The global syndemic of obesity, undernutrition, and climate change – three interconnected challenges – threatens both human and planetary health. This review focuses on one critical intersection: older populations living with overweight and obesity in the context of sustainable nutrition. Obesity and sarcopenia, particularly the co-occurrence called sarcopenic obesity, are often overlooked until the onset or exacerbation of other diseases necessitates secondary care. Preventing sarcopenic obesity requires reducing excess fat mass while preserving muscle mass and function. This involves lowering total energy intake while ensuring adequate protein intake in terms of quantity, quality, and distribution, combined with physical activity, particularly resistance exercise. Short-term studies show that both the source and dose of dietary protein significantly influence muscle protein synthesis rates. Longer-term studies examining the impact of plant-based diets on muscle health in older adults with or without overweight or obesity remain limited. Animal proteins have shown a modest advantage over most plant-based proteins in supporting muscle mass. Qualitative studies suggest that emphasizing both the health benefits and palatability of plant-based protein sources is key to promoting dietary changes in older adults. In older adults with obesity, it is challenging to combine energy restriction with higher protein intake, especially when protein sources are plant-based. To prevent and treat sarcopenic obesity in older adults and support planetary health, a shift toward more plant-based protein sources is required, while ensuring sufficient protein quantity and quality to preserve muscle health during weight loss.

Plant-based proteins are considered to be less effective in their capacity to stimulate muscle protein synthesis when compared with animal-based protein sources, likely due to differences in amino acid contents. We compared the postprandial muscle protein synthetic response following the ingestion of a lysine-enriched plant-based protein product with an isonitrogenous amount of chicken. Twenty-four men (age 24 ± 5 years; BMI 22·9 ± 2·6 kg·m−2) participated in this parallel, double-blind, randomised controlled trial and consumed 40 g of protein as a lysine-enriched wheat and chickpea protein product (Plant, n 12) or chicken breast fillet (Chicken, n 12). Primed, continuous intravenous l-(ring-13C6)-phenylalanine infusions were applied while repeated blood and muscle samples were collected over a 5-h postprandial period to assess plasma amino acid responses, muscle protein synthesis rates and muscle anabolic signalling responses. Postprandial plasma leucine and essential amino acid concentrations were higher following Chicken (P < 0·001), while plasma lysine concentrations were higher throughout in Plant (P < 0·001). Total plasma amino acid concentrations did not differ between interventions (P = 0·181). Ingestion of both Plant and Chicken increased muscle protein synthesis rates from post-absorptive: 0·031 ± 0·011 and 0·031 ± 0·013 to postprandial: 0·046 ± 0·010 and 0·055 ± 0·015 % h−1, respectively (P-time < 0·001), with no differences between Plant and Chicken (time x treatment P = 0·068). Ingestion of 40 g of protein in the form of a lysine-enriched plant-based protein product increases muscle protein synthesis rates to a similar extent as an isonitrogenous amount of chicken in healthy, young men. Plant-based protein products sold as meat replacers may be as effective as animal-based protein sources to stimulate postprandial muscle protein synthesis rates in healthy, young individuals.

Plant-derived proteins have been suggested to have less anabolic properties when compared with animal-derived proteins. Whether blends of plant- and animal-derived proteins can compensate for their lesser anabolic potential has not been assessed. The present study compares post-prandial muscle protein synthesis rates following the ingestion of milk protein with wheat protein or a blend of wheat plus milk protein in healthy, young males. In a randomised, double-blind, parallel-group design, 36 males (23 (sd 3) years) received a primed continuous L-[ring-13C6]-phenylalanine infusion after which they ingested 30 g milk protein (MILK), 30 g wheat protein (WHEAT) or a 30 g blend combining 15 g wheat plus 15 g milk protein (WHEAT+MILK). Blood and muscle biopsies were collected frequently for 5 h to assess post-prandial plasma amino acid profiles and subsequent myofibrillar protein synthesis rates. Ingestion of protein increased myofibrillar protein synthesis rates in all treatments (P < 0·001). Post-prandial myofibrillar protein synthesis rates did not differ between MILK v. WHEAT (0·053 (sd 0·013) v. 0·056 (sd 0·012) %·h−1, respectively; t test P = 0·56) or between MILK v. WHEAT+MILK (0·053 (sd 0·013) v. 0·059 (sd 0·025) %·h−1, respectively; t test P = 0·46). In conclusion, ingestion of 30 g milk protein, 30 g wheat protein or a blend of 15 g wheat plus 15 g milk protein increases muscle protein synthesis rates in young males. Furthermore, muscle protein synthesis rates following the ingestion of 30 g milk protein do not differ from rates observed after ingesting 30 g wheat protein or a blend with 15 g milk plus 15 g wheat protein in healthy, young males.