This present paper reviews the reliability and validity of visual analogue scales (VAS) in terms of (1) their ability to predict feeding behaviour, (2) their sensitivity to experimental manipulations, and (3) their reproducibility. VAS correlate with, but do not reliably predict, energy intake to the extent that they could be used as a proxy of energy intake. They do predict meal initiation in subjects eating their normal diets in their normal environment. Under laboratory conditions, subjectively rated motivation to eat using VAS is sensitive to experimental manipulations and has been found to be reproducible in relation to those experimental regimens. Other work has found them not to be reproducible in relation to repeated protocols. On balance, it would appear, in as much as it is possible to quantify, that VAS exhibit a good degree of within-subject reliability and validity in that they predict with reasonable certainty, meal initiation and amount eaten, and are sensitive to experimental manipulations. This reliability and validity appears more pronounced under the controlled (but more artificial) conditions of the laboratory where the signal: noise ratio in experiments appears to be elevated relative to real life. It appears that VAS are best used in within-subject, repeated-measures designs where the effect of different treatments can be compared under similar circumstances. They are best used in conjunction with other measures (e.g. feeding behaviour, changes in plasma metabolites) rather than as proxies for these variables. New hand-held electronic appetite rating systems (EARS) have been developed to increase reliability of data capture and decrease investigator workload. Recent studies have compared these with traditional pen and paper (P&P) VAS. The EARS have been found to be sensitive to experimental manipulations and reproducible relative to P&P. However, subjects appear to exhibit a significantly more constrained use of the scale when using the EARS relative to the P&P. For this reason it is recommended that the two techniques are not used interchangeably.

The prevalence of obesity is increasing in westernized societies. In the USA the age-adjusted prevalence of BMI ≫30 kg/m2 increased between 1960 and 1994 from 13 % to 23 % for people over 20 years of age. This increase in the prevalence of obesity has been attributed to an increased fat intake and a decreased physical activity. However, the role of the impact of the level of dietary fat intake on human obesity has been challenged. High-fat diets, due to their high energy density, stimulate voluntary energy intake. An increased fat intake does not stimulate its own oxidation but the fat is stored in the human body. When diet composition is isoenergetically switched from low to high fat, fat oxidation only slowly increases, resulting in positive fat balances on the short term. Together with a diminished fat oxidation capacity in pre-obese subjects, high-fat diets can therefore be considered to be fattening. Another environmental factor which could explain the increasing prevalence of obesity is a decrease in physical activity. The percentage of body fat is negatively associated with physical activity and exercise has pronounced effects on energy expenditure and substrate oxidation. High-intensity exercise, due to a lowering of glycogen stores, can lead to a rapid increase in fat oxidation, which could compensate for the consumption of high-fat diets in westernized societies. Although the consumption of high-fat diets and low physical activity will easily lead to the development of obesity, there is still considerable inter-individual variability in body composition in individuals on similar diets. This can be attributed to the genetic background, and some candidate genes have been discovered recently. Both leptin and uncoupling protein have been suggested to play a role in the prevention of diet-induced obesity. Indeed, leptin levels are increased on a high-fat diet but this effect can be attributed to the increased fat mass observed on the high-fat diet. No effect of a high-fat diet per se on leptin levels is observed. Uncoupling proteins are increased by high-fat diets in rats but no data are available in human subjects yet. In conclusion, the increased intake of dietary fat and a decreasing physical activity level are the most important environmental factors explaining the increased prevalence of obesity in westernized societies.

To study the intestinal metabolism of lignans, the concentrations of plant and mammalian lignans in intestinal digesta sampled along the intestinal tract of pigs were determined by isotope dilution GC–MS. The pigs were fed rye-bread diets made from either whole rye-grains or rye-grain milling fractions enriched in pericarp–testa, aleurone or endosperm cells. The content and characteristics of dietary fibre varied between diets and had been shown to induce different colon fermentation patterns. As the metabolism of lignans depends on the action of the intestinal flora, we tested whether the rye-bread diets influence the metabolism of lignans. In the ileum, the lignans were mainly present as conjugated plant lignans, which were determined only when the analytical procedure included a hydrolysis step. High recovery of dietary lignans in the ileum may indicate that the lignans enter the enterohepatic circulation. In addition, two to three times the intake of lignans were recovered in the faeces when the diets had a high content of dietary fibre suggesting underestimation of plant lignans in the diet. Most of the plant lignans disappeared from the intestinal tract between the terminal ileum and the caecum. The intestinal concentrations and the disappearance of lignans correlated with the content of lignans in the diet, being highest on the pericarp–testa diet and lowest on the endosperm diet. No effect of fermentation pattern on the intestinal metabolism of lignans was observed. The lignans were liberated from the pericarp–testa diet although the plant cell walls remained largely undegraded.

The present study examines the interactive effects of three fatty acids: myristic, palmitic and stearic acids, with dietary cholesterol, on lipoprotein metabolism in the hamster. Each saturated fatty acid was fed at a concentration of 100 g pure synthetic triacylglycerol/kg in the presence of 100 g triolein/kg and was fed in the presence of 0·05, 1·2 or 2·4 g dietary cholesterol/kg. Dietary cholesterol increased the concentration of cholesterol in each of the major plasma lipoprotein fractions. The largest effects on VLDL and LDL were seen in the presence of tripalmitin where the increase between the lowest and highest dietary cholesterol groups were 129 % and 38 % respectively. In contrast, HDL showed the greatest change in the tristearin group when the equivalent increase was 59 %. No interactive effects of dietary cholesterol and fat were seen on hepatic mRNA concentrations for the LDL receptor, hydroxymethylglutaryl-CoA reductase or the microsomal triacylglycerol transfer protein. As the amount of cholesterol in the diet increased, large differences were seen in the storage of hepatic cholesterol ester. At the highest dietary cholesterol intake the amount of hepatic cholesterol ester was 1·7-fold higher in the animals fed trimyristin compared with those fed tripalmitin. These results suggest that, as the amount of cholesterol in the diet is increased, palmitic acid becomes more hypercholesterolaemic. This is associated with a reduced ability to store cholesterol ester in the liver.

The main purpose of this study was to quantify the absorption of nutrients derived from carbohydrate assimilation in a model experiment with catheterised pigs. A low-fibre (LF) diet based on wheat flour and two high-fibre diets with added insoluble fibre from wheat bran (HFWB) or soluble fibre from oat bran (HFOB) were used. The diets were offered as baked rolls to three catheterised pigs in a 3×3 Latin square design. The pigs were surgically fitted with catheters placed in the portal vein and mesenteric artery and with an ultrasonic flow probe attached to the portal vein to monitor the blood-flow rate. The pigs were fed the diets three times daily and portal and arterial blood samples collected twice weekly up to 8 h after the morning feeding. Glucose, insulin, lactic acid (LA) and short-chain fatty acids (SCFA) were determined on the samples. The baseline level of glucose in the portal vein was about 6 mmol/l increasing to 10–11 mmol/l 20–30 min post-feeding with no difference among the different diets. Portal and arterial insulin mirrored portal glucose concentration and was also unaffected by the dietary composition. The net absorption of glucose (per 24 h) was: diet LF 4190 mmol; diet HFWB 3050 mmol and diet HFOB 3190 mmol corresponding to a recovery of 0·76–0·92 of ingested starch. The levels of LA and SCFA in the portal vein were relatively constant in the postprandial period. The net absorption of LA and SCFA was in the same order (749 and 720 mmol/d respectively) with diet LF, while LA was lower (384 and 582 mmol/d) and SCFA higher (738 to 891 mmol/d) when feeding the two high-fibre diets. There was a higher molar proportion of butyrate in the portal vein after feeding the high-fibre diet supplemented with oat bran as compared with the wheat-based diets.

The present study investigated the effects of the red microalga Porphyridium sp. on gastrointestinal physiology and lipid metabolism in male Sprague-Dawley rats. Diets containing dietary fibre from pelleted red microalgal cells (biomass) or their sulfated polysaccharide, pectin or cellulose (control) were fed to rats for a period of 30 d. All three fibre-supplemented diets increased the length of both the small intestine and colon, with a significantly greater effect in rats fed the algal polysaccharide. The polysaccharide also increased mucosa and muscularis cross-sectional area of the jejunum, and caused hypertrophy in the muscularis layer. The algal biomass significantly lowered gastrointestinal transit time by 44 % in comparison with the control rats. Serum and mucosal cholecystokinin levels were lower in rats on the pectin and polysaccharide diets, while cholecystokinin levels in rats fed algal biomass were not different from those in the control animals. In comparison with the control diet, all the experimental diets significantly lowered serum cholesterol levels (22–29 %). Feeding of non-fermentable algal polysaccharide or biomass significantly increased faecal weight and bile acid excretion compared with pectin-fed or control rats. The algal polysaccharide and biomass were thus shown to be potent hypocholesterolaemic agents active at low concentrations in the diet. Both metabolic and morphological changes were observed following consumption of algae, suggesting several possible mechanisms by which the alga affects lipid metabolism. The results presented in the present study encourage the use of red microalga as a functional food.

The present study was undertaken to study the metabolism of short-chain fatty acids (SCFA) by the reticulo-ruminal epithelium and the portal-drained viscera (PDV) under in vivo conditions with no interference from the metabolism of the rumen microbes. The technique of temporary isolation of the reticulo-rumen was applied to wethers implanted with catheters in a mesenteric artery, the hepatic portal vein and the right ruminal vein. Portal blood flow was measured by downstream dilution of p-aminohippuric acid; the PDV uptake of arterial acetate, as well as the whole-body irreversible loss rate (ILR) of acetate, was estimated by [2-13C] acetate infusion into the right ruminal vein. The sheep were maintained with a bicarbonate-buffered solution of SCFA in the reticulo-rumen along with continuous intraruminal infusion of SCFA for 4 h. The portal appearance of SCFA of non-reticulo-ruminal origin was estimated before and after the infusion protocol. Of the acetate absorbed by the sheep, 89 (SE 5), 109 (se 7) and 101 (se 7) % was recovered as portal net appearance of acetate, portal net appearance of acetate corrected for PDV uptake of arterial acetate and increase in the ILR of acetate respectively. Of the propionate, isobutyrate, butyrate, isovalerate and valerate absorbed by the sheep, 95 (se 7), 102 (se 9), 23 (se 3), 48 (se 5) and 32 (se 4) % respectively was recovered as portal net appearance. In contrast to current concepts, the present study showed that the reticulo-ruminal epithelium metabolizes none (or only a small proportion) of the acetate and propionate absorbed from the rumen. This observation could lead to the more efficient use of results obtained with multi-catheterized animals to quantify the net metabolite output of the rumen microbes.

The net absorption of amino acids (AA) in young pigs fed a barley-based control diet (C) and diets where barley was replaced by 200 g/kg fresh weight of dried lucerne (Medicago sativa; L20), white clover (Trifolium repens; W20) or perennial ryegrass (Lolium perenne; PR20) meal was studied. Castrated male pigs were fitted with permanent catheters in the hepatic portal vein and mesenteric artery, and the hepatic portal net absorption of AA was estimated from the porto–arterial plasma concentration differences and the hepatic portal-vein blood flow. In general, the essential AA (EAA) concentrations in the hepatic portal vein reached peak levels 90 min after feeding and thereafter exhibited a transient decline. Maximum porto–arterial differences were reached between 1 and 3 h postprandially for most of the AA. The cumulative net absorption of non-essential AA (NEAA) and EAA did not differ significantly between the barley-based diet and diets W20 and PR20. Due to a lower intake of AA on diet L20, the cumulative net absorption of NEAA and EAA was significantly (P<0·05) lower than diet C. With the exceptions of the EAA arginine, cystine and valine, and the NEAA glutamic acid + glutamine and glycine, there were no significant differences in the absorption coefficients for the EAA and NEAA between the diets. In addition, the pattern of the total EAA in the mixture absorbed postprandially did not differ significantly between the diets. The present study gives support to the contention that the replacement of barley AA with forage meal AA in a barley-based diet for growing pigs should be expected to result in minor differences in the net portal flux of AA.

Guinea-pig fetuses at term are mineralized to a degree comparable with human fetuses, which makes the guinea-pig an attractive animal model to study maternal–fetal interactions with regard to Ca and phosphate (P) homeostasis. We studied non-pregnant and pregnant (day 57) vitamin D-replete guinea-pigs, fed either a normal guinea-pig chow with 9·6 g Ca/kg and 4·9 g P/kg or a study diet with 2 g Ca/kg and 1 g P/kg (low-Ca–P diet) for 7–8 weeks. Both pregnancy and the low-Ca–P diet decreased plasma concentrations of 25-hydroxycholecalciferol (25(OH)D3), but increased total and free 1α,25-dihydroxycholecalciferol (1,25(OH)2D3), strongly suggesting an additive stimulation of 1α-hydroxylase activity. Maternal and fetal 25(OH)D3 and 1,25(OH)2D3 levels were highly correlated (r 0·82 and 0·92 respectively, P<0·001). Dual-energy absorption X-ray absorptiometry (DXA) showed that both pregnancy and the low-Ca–P diet decreased bone mineral density (BMD) of the maternal femur, particularly at the distal metaphysis. Despite higher 1,25(OH)2D3 concentrations and lower BMD, pregnant animals on the low-Ca–P diet were hypocalcaemic; blood Ca2+ levels were inversely correlated with the number of fetuses in this group (r -0·93, P<0·001). Fetal growth as well as mineralization (assessed by whole-body and femoral DXA, bone histomorphometry and plasma–bone osteocalcin measurements) were unaltered in the low-Ca–P group. In conclusion, fetal mineralization proceeds normally but induces maternal hypocalcaemia in guinea-pigs with dietary restriction of Ca and P.

Epidemiological studies indicate that moderate alcohol consumption, particularly wine, reduce the risk of CHD. The present study was designed to investigate the effect of grape-skin extract on markers of oxidative status. The study was designed as a randomised crossover. A diet with a low content of flavonoids was served with strict control of intake in two consecutive 1-week intervention periods to fifteen subjects (nine women, six men) divided randomly into two groups. During one of the weeks the subjects from either group consumed 200 ml grape-skin extract in water (1 mg extract/ml) at each of three daily meals (31·3 mg total phenolics, including 9·0 mg catechin). An increased activity of glutathione reductase and a borderline increase of glutathione peroxidase activity in erythrocytes were observed after grape-skin intervention, while the intervention had no significant effect on superoxide dismutase or catalase. Likewise, no effect was found on 2-aminoadipic semialdehyde (AAS) residues, a plasma protein oxidation product, or on malondialdehyde in plasma or in LDL, which are markers of lipoprotein oxidation. A marginal effect of grape-skin intervention was observed on plasma ascorbate levels. Intake of the experimental diet significantly reduced plasma vitamin C and plasma AAS in both groups. This effect was most pronounced in the particular week with no grape-skin extract addition. We speculate that grape-skin extract may have a sparing effect on vitamin C. The effects of the experimental diet may be partly ascribed to a low content of several fruit- and vegetable-related antioxidants like flavonoids and vitamin C and a relatively high content of carrot-derived antioxidants, such as carotenes.

The reduction in resting metabolic rate (RMR) during weight loss exceeds that accounted for by changes in body composition by 15%, suggesting that factors other than fat-free mass (FFM) explain the metabolic adaptation during food restriction in obesity. Our study aimed to establish if changes in the sympathoadrenal system activity, as inferred from an integrated measure such as 24 h urinary excretion of catecholamines, may play a role in the RMR adaptation observed during dietary restriction in obese patients. Ninety-three obese female subjects consumed a low-energy diet (LED) (2930 kJ/d (700 kcal/d)) for a 3-week period. At the beginning and at the end of the study, 24 h urinary excretion of catecholamines, FFM and RMR were measured. The LED induced a significant reduction in body weight (-3·3 (SEM 0·4) KG; P < 0·01), FFM (-1·9 (sem 0·7) kg; P < 0·01) and in the fat mass (-1·2 (sem 0·5) kg; P < 0·01). Noradrenalin excretion (24 h) decreased during the LED from 264 (sem 26) during a weight-maintenance period to 171 (sem 19) nmol/24 h after consumption of the LED for 3 weeks (P < 0·001); mean 24 h adrenalin excretion did not change during the LED (22 (sem 3) during the weight-maintenance period v. 21 (sem 3) nmol/24 h after consumption of the LED for 3 weeks; NS). The LED induced a significant decrease in RMR (7300 (sem 218) v. 6831 (sem 138) kJ/24 h; P < 0·001). The only independent variable that significantly explained variations in RMR both before and after consumption of the LED for 3 weeks, was FFM (r2 0·79 and r2 0·80 respectively). Urinary noradrenalin excretion explained a further 4 % of the variability in RMR, but only before the diet, so that a role of sympathoadrenal system on RMR seems to be present in obese patients in basal conditions but not at the end of the LED.

The present study aimed to compare the action of high-fat and high-carbohydrate (CHO) foods on meal size (satiation) and post-meal satiety in obese women. A within-subjects design was used; each participant received all four nutritional challenges. Fifteen healthy obese women (age 21–56 years, BMI 35–48 kg/m2) participated; thirteen completed all four test days. On two test days, participants were exposed to a nutritional challenge comprising an ad libitum high-fat or high-CHO lunch. On the other two test days they were exposed to a challenge comprising an ad libitum sweet high-fat or high-CHO mid-afternoon snack. Energy and macronutrient intakes were measured at each eating episode. Visual analogue rating scales were completed periodically to record subjective feelings of appetite. When offered a high-CHO selection of foods at lunch and mid-afternoon participants consumed less energy than when offered a high-fat selection. However, post-meal satiety was similar. Total test-day energy intake was significantly higher when high-fat foods were consumed at lunch, but not as a snack. Consumption of high-fat foods at a lunch and snack increased the amount of fat consumed over the whole test day. In conclusion, energy intake of an eating episode was influenced by nutrient composition in this group of obese women. Consumption of high-fat foods at lunch or as a snack led to overconsumption relative to high-CHO foods. However, high-fat foods at meals may have greater potential to influence daily intake than at snacks, probably because meals are larger eating episodes and therefore give greater opportunity to overconsume.

The objectives of the study were to determine: (1) daily energy expenditure (EE) of athletic and non-athletic adolescents of both sexes in free-living conditions; (2) day-to-day variations in daily EE during 1 week; (3) energy costs of the main activities; and (4) the effect of usual activity on EE during sleep, seated and miscellaneous activities. Fifty adolescents (four groups of eleven to fifteen boys or girls aged 16–19 years) participated in the study. Body composition was measured by the skinfold-thickness method, and VO2max and external mechanical power (EMP) by a direct method (respiratory gas exchanges) on a cycloergometer. Daily EE and partial EE in free-living conditions were computed from heart-rate (HR) recordings during seven consecutive days using individual prediction equations established from the data obtained during a 24 h period spent in whole-body calorimeters with similar activities. Fat-free mass (FFM), VO2max, EMP, daily EE and EE during sleep were significantly higher in athletic than in non-athletic subjects. After adjustment for FFM, VO2max, EMP, daily EE and EE during exercise were still higher in athletic than in non-athletic adolescents (P<0·001). However, adjusted sleeping EE was not significantly different between athletic and non-athletic adolescents. Increases in exercise EE were partly compensated for by significant reductions in EE during schoolwork and miscellaneous activities. Thus, the differences in daily EE between athletic and non-athletic subjects resulted mainly from increases in FFM and EE during exercise (duration and energy cost).

This study evaluated the tracking of energy and nutrient intakes, assessed by diet history, in a random sample of adolescents (boys n 225, girls n 230) at baseline (age 12 years), and subsequently at age 15 years. Median energy (MJ/d) and macronutrient (g/d) intakes increased significantly (all P<0·001) with increasing age in the boys. The girls' reported energy intake (MJ/d) remained stable over time, despite significant increases in BMI, weight and % body fat. Age-related changes in the girls' macronutrient intakes were inconsistent. When expressed in terms of nutrient density, the diets of both sexes became significantly richer, over time, in total folate (both sexes, P<0·01), but poorer in Ca (boys P<0·01, girls P<0·001) and riboflavin (both sexes P<0·001). Vitamin B6 (P<0·001) and Fe (P<0·05) densities increased in the boys, while the thiamin density of the girls' diets decreased (P<0·001). Tracking, defined as maintenance of rank over time, was summarised using weighted kappa statistics (κ). There were some significant changes in intakes at the group level; however, tracking of energy and nutrients in both sexes was only poor to fair (κ<0·40), indicating substantial drift of individuals between classes of intake over time. Particularly poor tracking was evident for % energy from sugars (κ 0·09) and total fat (κ 0·09) in the girls' diets. In conclusion, the poor to fair tracking observed in this cohort suggests that individual dietary patterns exhibited at 12 years of age are unlikely to be predictive of energy and nutrient intake at age 15 years.

Recasting the role of fruit and vegetables (F&V) in the diet, and planning national and international campaigns to enhance their consumption are major public health service objectives. The present study seeks to describe F&V availability patterns in ten European countries and examine compliance with current recommendations. The mean and median F&V availability (g/person per d) was estimated based on household budget survey data retrieved from the Data Food Networking (DAFNE) databank. Low F&V consumers were identified based on WHO international recommendations (minimum combined F&V intake of about 400 g/person per d) and current conservative guidelines of a minimum daily intake of three portions of vegetables and two portions of fruit. Considerable disparities in F&V availability were found among the surveyed European populations. Only in Mediterranean countries did the mean daily population intake clearly exceed combined F&V recommendations. Dietary patterns were positively skewed in all populations studied, on account of the presence of exceptionally high values among segments of the populations. Moreover, the correlation was unexpectedly weak between the proportion of low fruit and low vegetable consumers (Spearman's correlation coefficient +0·18). More than 50 % of the households in the surveyed populations are likely to consume less than the recommended daily vegetable intake of three portions, and this applies even to the two Mediterranean populations. The efficiency of F&V promoting strategies may be enhanced if F&V are addressed separately; furthermore, interventions that would specifically focus on vegetables are probably needed.

A randomised crossover dietary intervention study was performed to evaluate the effects of replacing meat protein in the diet with a soyabean product, tofu, on blood concentrations of testosterone, dihydrotestosterone, androstanediol glucuronide, oestradiol, sex hormone-binding globulin (SHBG), and the free androgen index (total testosterone concentration/SHBG concentration×100; FAI). Forty-two healthy adult males aged 35–62 years were studied. Diets were isoenergetic, with either 150 g lean meat or 290 g tofu daily providing an equivalent amount of macronutrients, with only the source of protein differing between the two diets. Each diet lasted for 4 weeks, with a 2-week interval between interventions. Fasting blood samples were taken between 07.00 and 09.30 hours. Urinary excretion of genistein and daidzein was significantly higher after the tofu diet (P<0·001). Blood concentrations of sex hormones did not differ after the two diets, but the mean testosterone:oestradiol value was 10 % higher (P=0·06) after the meat diet. SHBG was 3 % higher (P= 0·07), whereas the FAI was 7 % lower (P=0·06), after the tofu diet compared with the meat diet. There was a significant correlation between the difference in SHBG and testosterone:oestradiol and weight change. Adjusting for weight change revealed SHBG to be 8·8 % higher on the tofu diet (mean difference 3 (95 % CI 0·7, 5·2) nmol/l; (P=0·01) and testosterone:oestradiol to be significantly lower, P=0·049). Thus, replacement of meat protein with soyabean protein, as tofu, may have a minor effect on biologically-active sex hormones, which could influence prostate cancer risk. However, other factors or mechanisms may also be responsible for the different incidence rates in men on different diets.

The objective of the study was to examine the cariogenic potentials of maltodextrins and glucose syrups (two glucose polymers derived from starch) using a range of techniques in vitro and in laboratory animals. The experimental methods used were: (1) measurement of acid production from glucose syrups and maltodextrins by human dental plaque micro-organisms; (2) evaluation of the role salivary α-amylase in degrading oligosaccharides (degree of polymerisation >3) in the glucose polymers, estimating the products by HPLC; (3) assessment of the fermentability of trioses relative to maltose; (4) measurement of dental caries levels in three large-scale studies in laboratory rats fed on diets containing the glucose polymers. It was found that acid production from the glucose polymers increased as their higher saccharide content fell. Salivary α-amylase rapidly degraded the oligosaccharides (degree of polymerisation >3), mainly to maltose and maltotriose. In the presence of oral micro-organisms, maltotriose took longer to ferment than maltose, but by the end of a 2 h period the total amount of acid produced was the same from both. Incorporated into the diets in solid form, the glucose syrups and maltodextrins were associated with unexpectedly high levels of dental caries. In conclusion, the findings were unforeseen in the light of earlier data that a glucose syrup was less cariogenic than sucrose.