Disasters, whether natural or human-induced, present significant challenges and can lead to harmful outcomes for communities around the globe. According to United Nations Office for Disaster Risk Reduction (UNDRR), a disaster is defined as a serious disruption to the functioning of a community or a society at any scale due to hazardous events interacting with conditions of exposure, vulnerability, and capacity, leading to 1 or more of the following: human, material, economic, and environmental losses, and their impacts.1 Disasters are also classified into natural (geophysical, hydrological, meteorological, climatological, biological, and extra-terrestrial hazards) and human-induced (technological and societal hazards).2
Recognizing disaster types and their potential impacts are crucial for developing effective responses and mitigation strategies. They can be natural disasters, such as earthquakes, tsunamis, floods, cyclones, and pandemics, or human induced such as industrial accidents, terrorism, war, and road traffic accidents. The most frequently occurring natural disasters are earthquakes, tsunamis, floods, cyclones, and pandemic.Reference Martin3 The complexity of natural disasters significantly impacts the health of individuals, exacerbating existing health problems, damaging properties, and harming the environment.Reference Kreimer4 Mostly, priority is given to handling the short-term effects of natural disasters rather than long-term consequences, which may be as serious as their short-term consequences. Many of these long-term consequences can be prevented through simple lifestyle changes and modifications to the environment. Obesity is one such long-term consequence.Reference Qasim, Turcotte and De Souza5, Reference Jia, Cheng and Xue6
There is an increasing link between disaster aftermath and obesity, largely due to a lack of focus on the long-term effects of these events. According to World Health Organization (WHO), body mass index (BMI) is classified into normal (BMI between 18.5 and < 25 kg/m2), overweight (BMI ≥ 25 kg/m2 to < 30 kg/m2), and obese (BMI ≥ 30 kg/m2).7 Regardless of the long-term effects of natural disasters, the number of people with obesity has almost tripled since 1975, with the indices shifting from wealthy countries to poorer ones.8 In 2016, the WHO reported that 1.9 billion adults were overweight, with an additional 650 million classified as obese. Furthermore, in 2019, approximately 38.2 million children under the age of 5 were overweight or obese. In addition to that, in 2020, there were estimates that 39 million children and teenagers aged 5-19 years were affected by overweight or obesity.8, Reference Llewellyn, Simmonds and Owen9 In recent decades, natural disasters such as earthquakes, tsunamis, landslides, floods, and cyclones have affected over 2.6 billion individuals.10
The increasing prevalence of obesity significantly contributes to a range of short- and long-term health issues and imposing an economic burden on societies. Evidence has revealed that obesity is a major contributor to common noncommunicable diseases (NCDs),Reference Qasim, Turcotte and De Souza5, Reference Jia, Cheng and Xue6 and has serious consequences for both children and adults, causing physical and emotional problems, financial losses, and premature death.Reference Reilly and Kelly11 In addition, there is a heavy economic burden that directly impacts the health of individuals. A study predicted the economic burden of obesity if not intervened; the cost of overweight and obesity is expected to reach 3 trillion USD annually by 2030, and could rise to 18 trillion USD by 2060.Reference Okunogbe, Nugent and Spencer12 This highlights the urgent need for effective interventions, especially in a disaster context. Several studies have also revealed that sudden lifestyle changes during disasters can lead to overweight and obesity.Reference Reilly and Kelly11, Reference Moynihan, WAv and Igou13 Studies have shown that obesity is a complex issue during disasters, and sudden changes in lifestyle can lead to weight gain.Reference Reilly and Kelly11, Reference Moynihan, WAv and Igou13
A similar study identified a connection between natural disasters and the development of obesity and related issues.14 Understanding the specific risk factors that exacerbate obesity during disasters is crucial for addressing this growing issue. The main risk factors contributing to obesity during natural disasters are summarized as relocation, lack of access to amenities like playgrounds, sleep disturbances resulting from post-traumatic stress disorder, and stress experienced during pregnancy, which can also contribute to obesity and overweight.Reference Powell, Wegmann and Backode15–Reference Schulz17 Similarly, studies also identified that the death of close family members or friends during or after disasters, as well as being pregnant, can increase the likelihood of a child becoming obese in childhood.Reference Hohwü, Li and Olsen18 These factors highlight the immediate consequences of disasters and their long-lasting effects on community health.
Furthermore, disasters not only disrupt daily life but also hinder access to essential health care services, thus further intensifying the obesity crisis. This has been observed in instances such as floods in Ghana,Reference Codjoe, Gough and Wilby19 earthquakes in Japan,Reference Hasegawa, Murakami and Nomura20 earthquakes in Nepal,Reference Giri, Risnes and Uleberg21 and earthquakes in Haiti.Reference McIntyre, Hughes and Pauyo22 Such disruptions emphasize the need for effective public health strategies in disaster-prone areas. To prevent and manage obesity in normal circumstances, world bodies have developed different strategies to tackle overweight and obesity, such as the implementation of a school policy framework in 2008. This framework prioritizes diet-related issues, performing exercise, as well as health issues.23–25 The WHO also created a global action plan for physical activity spanning from 2018 to 2030 with the purpose of promoting and increasing movement to contribute to healthier individuals.26 A nonbinding agreement is the Sendai Framework for Disaster Risk Reduction 2015-2030 adopted by United Nations (UN) members advocating for disaster reduction. It focuses on 4 key priorities: understanding disaster risk, strengthening disaster risk governance, investing in disaster risk reduction for resilience, and enhancing disaster preparedness for effective response and recovery.27 If the effect of natural disasters on obesity is not prevented early, it will be hard for global bodies to achieve sustainable development goal 3, target 3.4, which is zero growth in prevalence of obesity, and reduce premature mortality from NCDs by one-third by 2030.
Obesity, once mainly a concern in high-income countries, is now a growing health issue in low- and middle-income nations.Reference Prentice and Jebb28 In addition to that, disasters exacerbate existing problems and significantly increase obesity, but planners and decision-makers have not adequately addressed the long-term consequences of disasters on obesity. It has serious implications for future generations because parental obesity has a positive impact on the degree of offspring obesity.Reference Dong, Wu and Chen29
Despite the importance of understanding the dynamics between natural disasters and obesity, there remains a significant knowledge gap regarding this relationship and its associated factors. Therefore, the current systematic review aimed to investigate all observational studies conducted on disasters and obesity, and synthesized them to provide comprehensive evidence to support policymakers and enable them to develop strategies to address overweight or obesity and associated factors in the aftermath of disasters.
Materials and Methods
This systematic review was conducted following the Preferred Systematic Review and Meta-analysis (PRISMA) guidelines.Reference Moher, Liberati and Tetzlaff30 Its protocol was registered as an international prospective register of systematic reviews with PROSPERO no: CRD 42024506070 and it is available at https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42024506070.
Searching Strategies
Electronic searches were conducted in PubMed/Medline, Web of Science, HINARI, Scopus, and Google Scholar to identify published articles that met the inclusion criteria for obesity or weight gain and their associated risk factors. Manual searches were also conducted to identify articles about prevalent forms of natural disasters, such as earthquakes, floods, tsunamis, cyclones, and hurricanes using the Boolean operators “AND/OR” to refine the search strategies. The search was guided by the PECO (Population, Exposure, Comparison, Outcome) framework to include articles involving individuals of all age groups whom reported being overweight or obese following natural disasters, risk factors for outcomes following disasters, individuals who developed overweight or obesity in comparison to those who did not after common natural disasters, and the presence of primary and secondary outcomes of overweight or obesity and their determinants following natural disasters.
Study Selection
The search terms were matched with relevant subject headings and searched as keywords in the title and abstract of the included databases. We used a predetermined and comprehensive search strategy that specifically examines the link between natural disasters and obesity or being overweight. This systematic review included all articles reporting either BMI and BMI z score and waist circumference, or both, without time restriction using these MeSH terms (((("Natural Disasters"[MeSH Terms] OR("Natural disaster"[MeSH Terms] OR “Earthquakes”[MeSH Terms] OR “Floods”[MeSH Terms] OR “Tsunamis”[MeSH Terms] OR “Cyclonic Storms”[MeSH Terms]) OR “Hurricane”[MeSH Terms]) AND ("Overweight"[MeSH Terms] OR “Paediatric Obesity”[MeSH Terms])) OR ("Obesity"[MeSH Terms] OR “obesity, abdominal”[MeSH Terms])) AND ((observational study[Filter]) AND (humans[Filter])). All articles that met the inclusion criteria were included in the current systematic review. They were extracted, summarized, and reported in the systematic review.
Inclusion and Exclusion Criteria
Inclusion: For this study, we examined articles that focused on observational study designs, including cohort, case-control, and cross-sectional studies. There were no restrictions on age or time. We also included articles that investigated the increase in body weight following natural disasters. This used BMI for adults and BMI z-score for children, in addition to waist circumference. According to the classification, body weight participants might be normal (BMI between 18.5 and < 25 kg/m2), overweight (BMI ≥ 25 kg/m2 to < 30 kg/m2), and obese (BMI ≥ 30 kg/m2).31 Waist circumference is a basic test to assess if someone has too much body fat or potential health issues. If a woman’s waist circumference is over 88 cm (35 inches) or a man’s is over 102 cm (40 inches), it may indicate the need to pay attention to their belly fat and overall health. It is not a diagnostic tool, but rather a screening tool.Reference Mason and Katzmarzyk32
Exclusion: The following criteria were used to exclude certain studies from our systematic review: human induced disasters, studies conducted on species other than humans, non-observational and qualitative study designs, editorial letters, articles written in languages other than English, articles that were inaccessible despite 2 attempts to contact the authors, and non-peer-reviewed articles.
Data Extraction
Two authors developed a Microsoft Excel template for data extraction and independently collected data after piloting and making subsequent changes. The essential characteristics that were included were the first author, year of publication, country, type of disaster, study design, study setting, total sample size, male proportion, study period, age, anthropometric measurements, prevalence of overweight or obesity, and all significant factors, as shown in Table 1.
Characteristics of included studies in systematic review
AHR, Adjusted Hazard Ratio; BMI, Body Mass Index; BMI SDS, Body Mass Index Standard Deviation Scores; CI, Confidence Interval; HDLC, high-density lipoprotein cholesterol; HbA1c, hemoglobin A1c or glycosylated hemoglobin; M5, Measurement 5; OR, Odd Ratio; PNMS, Postnatal Maternal Stress; SES, Socioeconomic Status; SBP, Systolic Blood Pressure.
Quality Assessments
Critical appraisal
The authors independently assessed the methodological quality of all 17 eligible studies using Joanna Briggs Institute (JBI) critical appraisal tools,Reference Moola, Munn and Tufanaru33 as shown in Table 1. The tools consist of 11 detailed questions with 4 possible answers: (1) Yes, (2) No, (3) Unclear, and (4) Not Applicable,Reference Moola, Munn and Tufanaru33 as shown in Appendix I. Conflicts were resolved through discussion and consensus among the authors. The findings of all eligible articles that scored above the average for all questions were synthesized and reported in narrative form.
Types of outcomes
The outcomes of interest in this review were obesity after natural disasters and its risk factors. We assessed weight increment based on weight indices and identified the risk factors associated with obesity in the aftermath of natural disasters.
Data analysis
Data analysis involved a narrative synthesis of the articles that passed the risk of bias assessment using the JBI critical appraisal tools mentioned above. The results were reported in a narrative format for both primary and secondary outcomes.
Results
Included Studies
A total of 2343 articles from databases and through searching through previously accessed references were gathered. Before we started reviewing, we excluded 81 articles that didn’t meet our requirements. We exported all of the articles to EndNote software version X9.3.3 for easier management, which automatically excluded 1746 articles. We couldn’t locate 7 articles, so we only had 509 left to access and review the full text according to our criteria. Finally, after going through all of that, we ended up with 17 articles that met our criteria and were included in the current systematic review. You can see the entire process in Figure 1.
PRISMA flow diagram for the search result of included studies.
Critical Appraisal
The quality of the 17 included articles was assessed using the JBI critical appraisal checklist. All the articles were above average according to the authors’ agreement. Some of the articles did not answer 2 questions of (1) Whether the follow-up was completed and (2) The reason for the loss of follow-up was not clear.
Characteristics of Included Studies
Seventeen relevant studies were included, with a total sample size of 229 058 participants that met the inclusion criteria. The smallest sample size was 103 participants,Reference Kroska, O’Hara and Elgbeili34 and the largest was 93 538.Reference Kikuya, Matsubara and Ishikuro35 Eleven of the included studies focused on children,Reference Kroska, O’Hara and Elgbeili34–Reference Hikichi, Aida and Kondo44 5 were conducted on adults,Reference Hikichi, Aida and Kondo44–Reference Takahashi, Yonekura and Sasaki48 and only 1 on adolescents.Reference Arlinghaus, Gorniak and Hernandez49 Geographically, most of the included studies (n = 12) were conducted in Japan,Reference Kikuya, Matsubara and Ishikuro35, Reference Yokomichi, Matsubara and Ishikuro36, Reference Isojima, Yokoya and Ono39–Reference Moriyama, Fuchimukai and Kondo42, Reference Hikichi, Aida and Kondo44–Reference Takahashi, Yonekura and Sasaki48, Reference Kuniyoshi, Kikuya and Matsubara50 followed by the USA,Reference Kroska, O’Hara and Elgbeili34, Reference Dancause, Laplante and Hart38, Reference Arlinghaus, Gorniak and Hernandez49 and Canada.Reference Dancause, Laplante and Fraser37, Reference Liu, Dancause and Elgbeili43 The research covered various natural disasters, with 7 studies on earthquakes,Reference Kikuya, Matsubara and Ishikuro35, Reference Yokomichi, Matsubara and Ishikuro36, Reference Ono, Isojima and Yokoya40–Reference Moriyama, Fuchimukai and Kondo42, Reference Uemura, Ohira and Yasumura47, Reference Kuniyoshi, Kikuya and Matsubara50 4 on a combination of earthquakes and tsunamis,Reference Isojima, Yokoya and Ono39, Reference Hikichi, Aida and Kondo44, Reference Takahashi, Yonekura and Tanno46, Reference Takahashi, Yonekura and Sasaki48 2 on floods,Reference Kroska, O’Hara and Elgbeili34, Reference Dancause, Laplante and Hart38 2 on storms,Reference Dancause, Laplante and Fraser37, Reference Liu, Dancause and Elgbeili43 and 1 on hurricanes.Reference Arlinghaus, Gorniak and Hernandez49 Both prospective and retrospective cohort study designs were utilized, with follow-up times ranging from 6 monthsReference Yokomichi, Matsubara and Ishikuro36 to 15.5 years.Reference Liu, Dancause and Elgbeili43 The minimum reported mean age of participants was 3 months,Reference Yokomichi, Matsubara and Ishikuro36 and the maximum was 67 years.Reference Uemura, Ohira and Yasumura47 The 17 included studies used various anthropometric measurements or indices, including only BMI,Reference Kroska, O’Hara and Elgbeili34, Reference Kikuya, Matsubara and Ishikuro35, Reference Dancause, Laplante and Fraser37, Reference Ono, Isojima and Yokoya40–Reference Moriyama, Fuchimukai and Kondo42, Reference Hikichi, Aida and Kondo44–Reference Takahashi, Yonekura and Tanno46, Reference Takahashi, Yonekura and Sasaki48, Reference Kuniyoshi, Kikuya and Matsubara50 BMI and waist circumference,Reference Liu, Dancause and Elgbeili43, Reference Uemura, Ohira and Yasumura47 BMI z-score for children and adolescents,Reference Dancause, Laplante and Hart38, Reference Moriyama, Fuchimukai and Kondo42, Reference Arlinghaus, Gorniak and Hernandez49 and 2 studies that measured BMI standard deviation score (SDS).Reference Isojima, Yokoya and Ono39, Reference Ono, Isojima and Yokoya40 A detailed summary of the included studies can be found in Table 1.
Change of Body Weight After Natural Disasters
Disaster management encompasses 4 essential phases: mitigation, preparedness, response, and recovery, each playing a crucial role at different stages.51 Overweight or obesity which is the byproduct of natural disasters occur during the recovery phase following natural disasters.52 Based on evidence, it can emerge with a timeframe of 7 monthsReference Takahashi, Yonekura and Sasaki48 to 6 years.Reference Zheng, Yokomichi and Matsubara41 To effectively manage these byproducts, early planning during the mitigation phase is key. Based on current systematic review all 17 included studies reported an increase in body weight following natural disasters. Five studiesReference Hikichi, Aida and Kondo44–Reference Takahashi, Yonekura and Sasaki48 focused on adult populations, while only 1 specifically targeted adolescents. Reference Arlinghaus, Gorniak and Hernandez49 Eleven studies examined the impact on children.Reference Kroska, O’Hara and Elgbeili34–Reference Liu, Dancause and Elgbeili43, Reference Kuniyoshi, Kikuya and Matsubara50 In adolescents, the prevalence of obesity increased by 5.79% in the aftermath of natural disasters.Reference Arlinghaus, Gorniak and Hernandez49 The studies presented different prevalence rates for obesity or overweight conditions. The smallest reported increase was 5.3%,Reference Moriyama, Fuchimukai and Kondo42 while the highest documented was 42.1%Reference Uemura, Ohira and Yasumura47 as shown in Table 1.
Determinant Factors
The systematic review identified risk factors that link natural disasters to overweight or obesity. These risk factors were classified as sociodemographic and socioeconomic (SES), limited access to healthy food, sedentary behavior, concerns related to maternal nutrition, child feeding practices, maternal psychological factors, unhealthy lifestyle behaviors, and factors related to location and displacement. This approach thoroughly analyzed the impact of natural disasters on overweight and obesity in people of all age groups as shown in Table 1.
Sociodemographic and socioeconomic factors
It was found that age and sex were significant risk factors for development of overweight or obesity after natural disasters. One study evaluated that being male and being older increased the likelihood of developing obesity.Reference Takahashi, Yonekura and Tanno46 Similarly, 2 studies showed a significant relation between childhood age and obesity after occurrence of natural disasters.Reference Yokomichi, Matsubara and Ishikuro36, Reference Liu, Dancause and Elgbeili43 Furthermore, 1 study evaluated that being a boy increased the probability of becoming obese.Reference Hikichi, Aida and Kondo44 However, 3 studies revealed that both sexes are at risk for obesity after natural disasters.Reference Yokomichi, Matsubara and Ishikuro36, Reference Uemura, Ohira and Yasumura47, Reference Takahashi, Yonekura and Sasaki48 As a determinant of health, SES is one of the important risk factors for health. High SES households were more likely to develop overweight or obesity in the aftermath of natural disasters.Reference Kroska, O’Hara and Elgbeili34
Access to unhealthy food and sedentary behavior
This systematic review examined the relationship between obesity and post-natural disaster risk factors. It is commonly observed that significant changes in lifestyles and eating habits occur following natural disasters. A study conducted on children showed that physical inactivity is a potential risk factor for obesity.Reference Yokomichi, Matsubara and Ishikuro36 Similarly, another study identified sedentary activities, such as prolonged comic book reading, altered walking habits to and from school, and excessive film watching as risk factors for obesity after disasters.Reference Moriyama, Fuchimukai and Kondo42 Additionally, frequent snacking was found to contribute to this phenomenon.Reference Moriyama, Fuchimukai and Kondo42 Consuming snacks after dinner and not skipping breakfast were significant risk factors for being overweight or obese after natural disasters.Reference Uemura, Ohira and Yasumura47 Furthermore, living in close proximity to supermarkets, food establishments, or bars was associated with an increased likelihood of obesity.Reference Takahashi, Yonekura and Sasaki48
Maternal nutritional status and child feeding
The nutritional status of the mother and feeding practices for the child have a significant impact on the child’s nutritional status and overall well-being. They can also enhance Intelligence Quotient (IQ), school performance, and even result in higher income in adulthood.Reference Victora, Bahl and Barros53 Three studies have found a significant association between high maternal BMI and increased risk of childhood obesity after natural disasters.Reference Kroska, O’Hara and Elgbeili34, Reference Dancause, Laplante and Fraser37, Reference Dancause, Laplante and Hart38 One of the studies specifically indicated that maternal height could potentially serve as a risk factor for overweight and obesity following natural disasters.Reference Dancause, Laplante and Fraser37 Another study found that the lack of breastfeeding was associated with an increased risk of obesity.Reference Dancause, Laplante and Fraser37 Additionally, a study reported that mixed feeding was also linked to obesity outcomes after natural disasters.Reference Kuniyoshi, Kikuya and Matsubara50
Maternal psychological factors
Two studies were conducted to investigate the link between the objective hardship stress experienced by mothers and the increased risk of childhood overweight or obesity.Reference Dancause, Laplante and Hart38, Reference Liu, Dancause and Elgbeili43 Additionally, 3 studies examined maternal subjective hardship stress.Reference Kroska, O’Hara and Elgbeili34, Reference Dancause, Laplante and Hart38, Reference Liu, Dancause and Elgbeili43 Moreover, 1 study indicated that maternal generalized stress was a contributing factor to obesity.Reference Dancause, Laplante and Hart38 Previous maternal exposure to natural disasters, specifically floodsReference Yokomichi, Matsubara and Ishikuro36 and tsunamis,Reference Zheng, Yokomichi and Matsubara41 was also identified as a general risk factor.Reference Kikuya, Matsubara and Ishikuro35, Reference Dancause, Laplante and Fraser37 Furthermore, a study highlighted that insufficient social support during natural disasters could potentially contribute to childhood overweight and obesity.Reference Kroska, O’Hara and Elgbeili34
Unhealthy behavioral lifestyle
Healthy behaviors are actions taken to promote and maintain good health, while unhealthy behaviors are actions that harm health.Reference Mokdad, Marks and Stroup54 A recent systematic review identified a study that reported a significant association between alcohol consumption before and after natural disasters and obesity.Reference Uemura, Ohira and Yasumura47 Similarly, 2 studies found that quitting smoking was statistically linked to increased obesity following natural disasters.Reference Uemura, Ohira and Yasumura47, Reference Takahashi, Yonekura and Sasaki48
Location and displacement related factors
Three studies found a link between individuals whose homes collapsed and a higher prevalence of obesity or being overweight.Reference Kikuya, Matsubara and Ishikuro35, Reference Dancause, Laplante and Fraser37, Reference Zheng, Yokomichi and Matsubara41 Researchers identified that living near coastal areas and proximity to nuclear power plants were associated with an increased likelihood of being overweight or obese.Reference Ono, Isojima and Yokoya40 Evacuees or displaced people were more prone to developing obesity compared to non-evacuees, according to 3 studies.Reference Kikuya, Matsubara and Ishikuro35, Reference Ohira, Hosoya and Yasumura45, Reference Uemura, Ohira and Yasumura47 Non-displacement was negatively associated with obesity, and obesity was decreased from 26.9% to 26.6%.Reference Hikichi, Aida and Kondo44 Regardless of whether individuals were living in temporary or permanent settlements, there was a risk of being overweight or obese, according to 3 studies.Reference Takahashi, Yonekura and Tanno46–Reference Takahashi, Yonekura and Sasaki48 A study with similar findings demonstrated that individuals living in temporary housing tended to gain weight, regardless of their sex or previous BMI.Reference Takahashi, Yonekura and Sasaki48 Moreover, the duration of residing in temporary housing versus permanent housing had a significant impact on body weight gain for both sexes following natural disasters, according to 2 studies.Reference Takahashi, Yonekura and Tanno46, Reference Takahashi, Yonekura and Sasaki48
Discussion
This is the first comprehensive review to examine the relationship between obesity and natural disasters. Its primary objective was to synthesize overweight or obesity and report it, while the secondary objective was to identify factors influencing this link, which is crucial for developing strategies to reduce obesity after natural disasters. In total, 17 studies involving 229 058 participants were included in the review. All eligible studies reported significant increases in overweight or obesity prevalence following natural disasters in both children and adults. The determinant factors were grouped into several categories, including sociodemographic and SES factors, access to unhealthy food, sedentary behavior, maternal nutrition-related issues, child feeding practices, maternal psychological factors, unhealthy lifestyle behaviors, and location- or displacement-related issues. These findings highlight the complex interplay between disaster-induced factors and their impact on health, like overweight or obesity.
Children are particularly vulnerable during and after natural disasters, which can increase the risk of developing overweight or obesity. Eleven studies have reported an increase in overweight or obesity among children following natural disasters.Reference Kroska, O’Hara and Elgbeili34–Reference Hikichi, Aida and Kondo44 In contrast, 2 studies have found that children experience undernutrition in the aftermath of such events.Reference Zhao, Yu and Huang55, Reference Zhao, Yin and Zhao56 Similarly, research conducted in Haiti and China has observed cases of undernutrition across various childhood age groups.Reference Ayoya, Heidkamp and Ngnie–Teta57, Reference Dong, Ge and Zhao58 The possible reasons for this discrepancy may be studies in Haiti and other low-income countries have reported that limited access to nutritious foods, clean water, and sanitation contributes to undernutrition.Reference Gaire, Delbiso and Pandey59–Reference Del Ninno, Dorosh and Smith61 Additionally, increased episodes of diarrhea due to bottle feeding contribute to decreased BMI.Reference Yokomichi, Matsubara and Ishikuro62 A disrupted food supply chain caused by damaged transportation routes is another cause of undernutrition.Reference Shozugawa, Nogawa and Matsuo63 Conversely, overweight and obesity are due to natural disasters disrupting normal lifestylesReference Lai, La Greca and Colgan16, Reference Codjoe, Gough and Wilby19, Reference Kroska, O’Hara and Elgbeili34–Reference Zheng, Yokomichi and Matsubara41, Reference Liu, Dancause and Elgbeili43–Reference Takahashi, Yonekura and Sasaki48, Reference Arcaya, James and Rhodes64 and physical inactivity.Reference O’Brien, Nader and Houts65 Moreover, a study explained that one of the main reasons for the increase in obesity among children following natural disasters is that parents restrict outdoor play due to fear of environmental hazards.Reference McCurry66
The current systematic review identified age and sex as risk factors for overweight or obesity. Two studies highlighted age and sex,Reference Yokomichi, Matsubara and Ishikuro36, Reference Liu, Dancause and Elgbeili43 whereas, 1 study focused on male sex alone.Reference Yokomichi, Matsubara and Ishikuro36 Across age groups, overweight or obesity are not evenly distributed. BMI of children aged 42 months or above is higher than that of children younger than 42 months.Reference Yokomichi, Matsubara and Ishikuro36, Reference Liu, Dancause and Elgbeili43 The possible reasons may be parents restricting outdoor activities and reducing the opportunity to exercise because of possible hazards.Reference McCurry66, Reference Tremblay, LeBlanc and Carson67 At this age, children who were more active may experience higher levels of stress due to parents’ restrictions, leading to sleeplessness and preventing them from engaging in outdoor activities and exercise, resulting in an increased risk of overweight and obesity after natural disasters. Additionally, the fear of environmental hazards and the possibility of future disasters can further exacerbate these issues, as parents may continue to restrict their children’s outdoor activities.
Another important determinant was sedentary behavior that increases the risk of all causes of morbidity and mortality, including overweight or obesity. A sedentary behavior refers to sitting, reclining, or lying down with an energy expenditure of less than 1.5 metabolic equivalents (METs).Reference Clemes, O’Connell and Edwardson68 Sedentary behavior can occur in educational settings, at home, and during travel.69 Two studies found that increased access to technology leads to prolonged sitting time,Reference Kadouh and Acosta70, Reference Jakicic and Davis71 which, along with extended TV watching, contributes to excessive weight gain.Reference Kadouh and Acosta70, Reference Segal, Lacayanga and Dunaif72 Disruption of infrastructure due to natural disasters also is a risk factor for weight gain.Reference Tsuboyama-Kasaoka, Hoshi and Onodera73 Adopting a healthy lifestyle, including a balanced diet, regular exercise, and minimising risk factors, remains the most commonly effective strategy for preventing obesity.Reference Malekzadeh, Mohamadnejad and Merat74 Notably, physical exercise accounts for 20-30% of daily energy expenditure.Reference Kadouh and Acosta70, Reference Segal, Lacayanga and Dunaif72 This indicates that sedentary behavior is a key risk factor for obesity, especially when combined with reduced physical activity opportunities and parental restrictions on outdoor activities, which significantly diminish exercise opportunities.Reference Tremblay, LeBlanc and Carson67, 69, Reference Scharadin, Zanocco and Chistolini75
SES is another significant risk factor for overweight and obesity in the aftermath of natural disasters. A previous study found that high SES is associated with weight gain.Reference Kroska, O’Hara and Elgbeili34 Conversely, 2 studies reported that low SES also contributes to weight gain.Reference Ng and Jeffery76, Reference Gray77 The possible reasons for an increase in weight gain among low-income individuals including the tendency to choose cheaper, unhealthy foods, increased stress leading to poor dietary habits, and stress-related eating behaviors, or emotional eating disorders during natural disasters.Reference Ng and Jeffery76, Reference Gray77
Maternal factors, such as anthropometric indices, play a role in childhood obesity caused by natural disasters. High maternal BMI beforeReference Kroska, O’Hara and Elgbeili34, Reference Dancause, Laplante and Fraser37, Reference Dancause, Laplante and Hart38 and during pregnancy,Reference Kadouh and Acosta70, Reference Baptiste-Roberts, Nicholson and Wang78 maternal smoking during pregnancy,Reference Oken, Levitan and Gillman79 caesarean section,Reference Kadouh and Acosta70, Reference Lifschitz80 gestational diabetes,Reference Baptiste-Roberts, Nicholson and Wang78 and short maternal stature are associated with an increased risk of childhood obesity.Reference Dancause, Laplante and Fraser37 The possible reasons for childhood obesity may be intergenerational in nature, and hormonal imbalance, such as adrenocorticotropic hormone, corticosterone, and catecholamines triggered by disasters, affects appetite and contributes to offspring overweight or obesity.Reference Dong, Wu and Chen29
Breastfeeding is one of the most effective ways of ensuring health and survival. Breastfeeding provides several benefits for children, such as providing energy and nutrients, improving intelligence, and being less prone to diabetes, overweight or obesity. Available evidence suggests that exclusive breastfeeding enhances infant and child health and reduces morbidity and mortality.Reference Lopez-Alarcon, Villalpando and Fajardo81, Reference Perera, Ganesan and Jayarasa82 Another similar study identified that exclusive breastfeeding promotes optimal weight gain and protects against overweight or obesity.Reference Owen, Martin and Whincup83 Conversely, not breastfeedingReference Dancause, Laplante and Fraser37 or shorter periods of breastfeeding with mixed feeding,Reference Kuniyoshi, Kikuya and Matsubara50 can lead to overweight or obesity. A previous systematic review and meta-analysis found that breastfeeding decreases the risk of becoming overweight.Reference Horta, Rollins and Dias84 Furthermore, a comparative study revealed that infants who receive expressed breast milk have a higher risk of obesity than those who are directly breastfed, emphasizing the importance of direct breastfeeding.Reference McCarthy85 Despite the presence of microbiota in human milk either expressed or direct breastfed, and other factors that help maintain a healthy immune balance, exerting an obesity prevention effect found in the digestive tract of breastmilkfed children.Reference Enaud, Prevel and Ciarlo86, Reference Hufnagl, Pali-Schöll and Roth-Walter87 A possible reason for expressed breast milk being linked to obesity may be due to potential overfeeding of a child when caregivers may encourage excessive bottle feeding when the mother is unavailable, which can lead to mixed feeding. Furthermore, the nutritional degradation that occurs during storage might reduce some of the health benefits, potentially influencing infants’ overweight or obesity after natural dissters.
Moreover, maternal psychological issues during or following a natural disaster also significantly influence childhood obesity. Factors such as subjective hardship stress,Reference Kroska, O’Hara and Elgbeili34, Reference Dancause, Laplante and Hart38, Reference Liu, Dancause and Elgbeili43 stress resulting from both subjective and objective hardship stress,Reference Dancause, Laplante and Hart38, Reference Liu, Dancause and Elgbeili43 general stress,Reference Dancause, Laplante and Hart38 negative experiences during flood events,Reference Yokomichi, Matsubara and Ishikuro36 negative tsunami experiences,Reference Zheng, Yokomichi and Matsubara41 severe experiences of natural disasters,Reference Kikuya, Matsubara and Ishikuro35 exposure to multiple stressful events,Reference Dancause, Laplante and Fraser37 and lack of social supportReference Kroska, O’Hara and Elgbeili34 contribute to overweight and obesity following natural disasters. Our findings are consistent with a previous study which revealed that prenatal maternal stress contributed to childhood overweight or obesity.Reference Whitaker, Pepe and Wright88 In addition, increased activity of serotonergic neurons and levels of tryptophan for adults contribute to excessive consumption of carbohydrate-rich, low-protein meals, resulting in weight gain.Reference Cooke and Hole89 It’s very important to focus on preventing childhood obesity by improving maternal health, early healthy eating behaviors, physical activity according to WHO recommendations, adequate sleep, and decreasing screen time for all children under 5.
Interestingly, adolescents and adults are also not immune to the effects of overweight or obesity following the occurrence of natural disasters. Six of the included studies reported that they developed overweight or obesity due to sedentary behavior, and sociodemographic, socioeconomic, psychological, and behavioral factors.Reference Hikichi, Aida and Kondo44–Reference Arlinghaus, Gorniak and Hernandez49
As age increases, the probability of becoming obese also increases. Two of the included studies found that male sex and age > 57 years were key determinants of overweight or obesity.Reference Liu, Dancause and Elgbeili43, Reference Takahashi, Yonekura and Tanno46 There are several possible explanations for this trend. As people age, hormonal changes, such as the decline of growth and leptin hormones, lead to metabolic slowdown.Reference Pataky, Young and Nair90, Reference Rolls91 Additionally, sensory perception of taste and smell can decline and lead to loss of appetite and choosing inadequate nutritious foods.Reference de Jong, Mulder and de Graaf92, Reference Duffy, Backstrand and Ferris93 Increased physical inactivity is also related to age,Reference O’Brien, Nader and Houts65 and reduced social activities can lead to increased depressive symptoms and affect appetite.Reference Kawaharada, Sugimoto and Uchida94 In addition, both subjective and objective causes of stress can lead to emotional eating of unhealthy foods.Reference Calderón-Asenjo, Jalk-Muñoz and Calizaya-Milla95 Furthermore, natural disasters can limit access and affordability of fresh foods, resulting in a diet high in sugar and calories, ultimately exacerbating the risk of obesity.Reference Shozugawa, Nogawa and Matsuo63, Reference Tsuchida, Isobe and Watanabe96–Reference Mendez and Grissom98
The study also underscores SES as a risk factor for overweight and obesity following natural disasters. Specifically, individuals with high SES are more likely to experience weight gain during disasters.Reference Kroska, O’Hara and Elgbeili34 However, current evidence has identified that the burden of SES is shifting from high to low-income individuals, and rural residents instead of urban residents.Reference Mendez, Monteiro and Popkin99, Reference Monteiro, Moura and Conde100 Another study stated that the prevalence of obesity is higher among individuals with the lowest SES compared with their higher SES counterparts.Reference Park and Ko101 Similarly, 2 studies found that individuals with low SES are at greater risk of overweight or obesity.Reference Drewnowski, Moudon and Jiao102, Reference Wang and Beydoun103 During disaster, households with low SES often choose cheaper, unhealthy foods over expensive and nutritious alternatives.Reference Ng and Jeffery76 The possible reason for developing low SES-based obesity may be the financial constraint on access to health facilities, contributing to the obesity epidemic among vulnerable populations.Reference Tan, Min and Xue104 The reliance of unhealthy foods such as high-energy processed and saturated fats may contribute to overweight and obesity during disasters. Although both the high and low SES groups are at risk of developing overweight or obesity, individuals with low SES face a greater risk because of limited access to healthy foods.
Additionally, physical activity plays a crucial role in maintaining a healthy weight and lifestyle. The WHO defines physical activity as any movement driven by skeletal muscles that requires energy expenditure. Activities performed for recreation, transportation, or work can range from light to intense exercise, all of which contribute to better health.105 Natural disasters are inversely correlated with normal lifestyles, and enhance sedentary lifestyle, ease of access to unhealthy food, and development of unhealthy behaviors. Evidence has shown that access to technology leads to prolonged sitting time and enhances excessive weight gain.Reference Kadouh and Acosta70, Reference Jakicic and Davis71 Improving healthy lifestyle habits, such as consuming a nutritious diet and engaging in regular exercise which accounts for 20-30% of daily energy expenditure, plays a significant role in reducing overweight and obesity, both under normal conditions and during natural disasters.Reference Kadouh and Acosta70, Reference Segal, Lacayanga and Dunaif72, Reference Malekzadeh, Mohamadnejad and Merat74
While breakfast consumption can support weight management, poor food choices or excessive calorie intake can contribute to weight gain. Moreover, abstaining from skipping breakfast has been identified as a risk factor for weight gain.Reference Uemura, Ohira and Yasumura47 In contrast, 2 separate studies conducted on preschoolers and adolescents have indicated that skipping breakfast is associated with increased abdominal adiposity.Reference Kesztyüs, Traub and Lauer106, Reference Alexander, Ventura and Spruijt‐Metz107 The plausible mechanism underlying this finding could be attributed to energy depletion, which prompts the utilization of stored fat and subsequently results in weight loss. However, the possible explanations for weight gain may include unhealthy breakfast choices, increased overall caloric intake, false sense of nutritional balance, and disrupted hunger cues.
Maternal psychology during and after natural disasters as mentioned aboveReference Kroska, O’Hara and Elgbeili34–Reference Dancause, Laplante and Hart38, Reference Zheng, Yokomichi and Matsubara41, Reference Liu, Dancause and Elgbeili43 is associated unhealthy maternal weight gain. This finding is consistent with previous research, which revealed that maternal stress contributes to increased abdominal adiposity.Reference Liu, Dancause and Elgbeili108 The possible explanation is that stress can lead to emotional eating, characterized by consumption of high-energy foods, as well as prolonged sedentary behavior after natural disaster. Hormonal imbalance during stress increases activity of serotonergic neurons and elevated tryptophan levels, which may contribute to excessive consumption of carbohydrate-rich, low-protein meals, resulting in weight gain.Reference Cooke and Hole89
According to the WHO, quitting smoking has immediate and long-term benefits, including increasing life expectancy and preventing various health issues, such as impotence, premature birth, low birth weight (LBW) babies, asthma, and ear infections, active smokers and second-hand or passive smokers.109 One study found a link between disasters, smoking cessation, and abdominal obesity.Reference Uemura, Ohira and Yasumura47 A similar study identified quitting smoking as a risk factor for obesity.Reference Pisinger and Jorgensen110 Another study reported weight gain after quitting smoking.Reference Williamson, Madans and Anda111 Conversely, 3 studies have shown that quitting smoking before or after a disaster reduced weight.112–Reference Clair, Chiolero and Faeh114 Similarly, 1 study aligns with this, as nonsmokers were less likely to be obese compared to with smokers.Reference Audrain‐McGovern and Benowitz115 The possible reason for increasing weight after quitting smoking post-disaster include nicotine withdrawal, which contributes to increased food consumption and decreased energy expenditure, potentially increasing the risk of obesity.Reference Filozof, Fernandez Pinilla and Fernández‐Cruz116 Other reasons for quitting smoking include concerns about family members’ health, lack of designated smoking areas, and overall health concerns. Overall, smoking poses significant risks to respiratory health, decreases lung function, intensifies asthma, causes chronic obstructive pulmonary disease, and contributes to cardiovascular problems. Quitting smoking can help prevent all these issues, including financial-related issues.
According to the WHO, alcohol is a toxic and psychoactive substance that causes dependency and contributes to 3 million deaths globally each year, as well as disabilities and poor health for millions of people. It is also a leading risk factor of premature mortality.117 This study found that alcohol consumption was a risk factor for overweight and obesity during and after natural disasters.Reference Uemura, Ohira and Yasumura47 A previous study found that alcohol consumption is associated with increased total energy intake and excessive weight gain.Reference Schröder, Morales-Molina and Bermejo118 Similarly, a systematic review and meta-analysis showed that alcohol consumption causes abdominal obesity in men.Reference Bendsen, Christensen and Bartels119 It is reasonable to assume that alcohol consumption exceeds the daily required energy, and the body converts it into fat, resulting in overweight and obesity, which worsen during and after disasters when people are inactive in that setting and/or physically inactive after consuming alcohol.
Obesity is the result of a mix of biological, environmental, and behavioral influences, including excessive energy intake and insufficient energy expenditure.Reference Hill and Commerford120, Reference Walley, Blakemore and Froguel121 Notably, individuals displaced by natural disasters are at a higher risk for developing obesity, particularly in temporary housing situations where access to healthy food is often limited.Reference Kikuya, Matsubara and Ishikuro35, Reference Ohira, Hosoya and Yasumura45 Likewise, 2 additional studies showed that residing in temporary housing is associated with a higher likelihood of being overweight or obese.Reference Uemura, Ohira and Yasumura47, Reference Takahashi, Yonekura and Sasaki48 After natural disasters, most public and private facilities were either completely or partially destroyed, leading to a sedentary lifestyle for the entire community.Reference Davison and Lawson122 Additionally, there is an increase in the consumption of high-energy foods, resulting in an excess energy consumption. Another significant risk factor for obesity was living in coastal areas.Reference Ono, Isojima and Yokoya40 One possible reason is that people have easy access to seafood, as well as food distribution during disasters. Coastal residents have numerous options to obtain unhealthy foods which are processed foods because of fear of contaminated seafood after disasters, as disasters are less likely to disrupt the transportation compared to other areas. Similarly, the other possible reasons for overweight and obesity after natural disasters may be limited access to healthy foods and physical inactivates.Reference Scharadin, Zanocco and Chistolini75 Moreover, low SES leads to limited access to health facilities.Reference Gray77
Conclusion
The conclusion of this paper highlights that natural disasters significantly contribute to increased rates of overweight or obesity in both children and adults. The review synthesizes evidence from 17 studies, showing that disaster-related factors such as socioeconomic conditions, limited access to healthy food, increased sedentary behavior, maternal health, psychological stress, and lifestyle changes play key roles in exacerbating obesity risk. Vulnerable populations, including children, low-income individuals, and those displaced by disasters, are particularly affected.
To mitigate the impact of natural disasters on obesity, a comprehensive approach is needed, focusing on promoting healthy lifestyles, improving access to nutritious food, encouraging physical activity, and addressing stress-related behaviors. Special attention should be given to high-risk groups such as children and those of lower SES. Ultimately, targeted strategies are crucial to reducing the long-term health consequences of natural disasters and preventing the growing epidemic of obesity in disaster affected populations. Promoting community gathering initiatives to empower informed food choices and stress management are important to prevent overweight or obesity.
Strengths and Limitations
This study is the first review ever done on the topic of overweight and obesity after natural disasters and their related risk factors. With climate change, more natural disasters are happening around the world, and this issue is a big problem globally. This research gives us valuable insights about disasters’ effect on obesity and their risk factors in the aftermath of disasters. Despite its strengths, the paper has several limitations. Firstly, the quality of the included studies varies, which may affect the reliability of the findings. Secondly, the lack of standardized definitions for obesity and related factors across studies complicates data comparisons. Thirdly, the geographical context of the studies may limit the generalizability of the findings, as many focus on specific regions. Most of the studies we looked at are from a few specific countries. Fourthly, this systematic review did not include all types of disasters, like biological disasters. Finally, we only considered papers written in English for this study, which is more likely to have a risk of publication bias.
Study Implications
To our knowledge, this systematic review is the first to examine the link between post-natural disasters and obesity. The findings of the study suggest that there is a limited understanding of obesity following natural disasters. Obesity is a complex issue that contributes to chronic diseases, highlighting the need to address the factors that contribute to obesity after natural disasters to implement effective prevention and control strategies.
Supplementary material
The supplementary material for this article can be found at http://doi.org/10.1017/dmp.2024.347.
Data availability statement
The data for this systematic review is available in this research paper and the authors’ records.
Acknowledgments
We would like to acknowledge all our colleagues who encouraged us and supported indirectly to perform this systematic review.
Author contribution
The authors have been involved in every stage of the study. TY and KHA were responsible for planning, conducting literature searches, performing critical appraisal and quality assessments, and data extraction. TY drafted the manuscript, KHA reviewed and revised it, and finally proofread it. Then, both authors approved the final version for publication.
Funding statement
The authors have stated that they did not receive any financial support from any institution or publishing entity for conducting and the publication of this systematic review.
Competing interest
The authors stated that there are no conflicts of interest, authorship disputes, or competing interests associated with the publication of this article.
Ethical standard
This systematic review was conducted utilizing publicly available secondary data, which did not entail the involvement of either animal or human subjects, and, thus, did not necessitate ethical approval.
Open access
