The European Food Safety Authority has suggested that EU countries implement the 2 × 24 h diet recall (2 × 24 h DR) method and physical activity (PA) measurements for national dietary surveys. Since 2000, Denmark has used 7 d food diaries (7 d FD) with PA questionnaires and measurements. The accuracy of the reported energy intakes (EI) from the two diet methods, pedometer-determined step counts and self-reported time spent in moderate-to-vigorous PA (MVPA) were compared with total energy expenditure measured by the doubly labelled water (TEEDLW) technique and with PA energy expenditure (PAEE), respectively. The study involved fifty-two male and sixty-eight female volunteers aged 18–60 years who were randomly assigned to start with either the 24 h DR or the web-based 7 d FD, and wore a pedometer for the first 7 d and filled in a step diary. The mean TEEDLW (11·5 MJ/d) was greater than the mean reported EI for the 7 d FD (9·5 MJ/d (P < 0·01)) but the same as the 2 × 24 h DR (11·5 MJ/d). The proportion of under-reporters was 34 % (7 d FD) and 4 % (2 × 24 h DR). Most participants preferred the 7 d DR as it was more flexible, despite altering their eating habits. Pearson’s correlation between steps corrected for cycling and PAEE was r = 0·44, P < 0·01. Spearman’s correlation for self-reported hours spent in MVPA and PAEE was r = 0·58, P < 0·01. The 2 × 24 h DR performs better than the existing 7 d FD method. Pedometer-determined steps and self-reported MVPA are good predictors of PAEE in adult Danes.

Physical activity questionnaires (PAQ) could be suitable tools in free-living people for measures of physical activity, total and activity energy expenditure (TEE and AEE). This meta-analysis was performed to determine valid PAQ for estimating TEE and AEE using doubly labelled water (DLW). We identified data from relevant studies by searching Google Scholar, PubMed and Scopus databases. This revealed thirty-eight studies that had validated PAQ with DLW and reported the mean differences between PAQ and DLW measures of TEE (TEEDLW − TEEPAQ) and AEE (AEEDLW − AEEPAQ). We assessed seventy-eight PAQ consisting of fifty-nine PAQ that assessed TEE and thirty-five PAQ that examined AEE. There was no significant difference between TEEPAQ and TEEDLW with a weighted mean difference of –243·3 and a range of –841·4 to 354·6 kJ/d, and a significant weighted mean difference of AEEDLW – AEE PAQ 414·6 and a range of 78·7–750·5. To determine whether any PAQ was a valid tool for estimating TEE and AEE, we carried out a subgroup analysis by type of PAQ. Only Active-Q, administered in two seasons, and 3-d PA diaries were correlated with TEE by DLW at the population level; however, these two PAQ did not demonstrate an acceptable limit of agreement at individual level. For AEE, no PAQ was correlated with DLW either at the population or at the individual levels. Active-Q and 3-d PA diaries were identified as the only valid PAQ for TEE estimation. Further well-designed studies are needed to verify this result and identify additional valid PAQ.

Recently there has been a considerable rise in the frequency of metabolic diseases, such as obesity, due to changes in lifestyle and resultant imbalances between energy intake and expenditure. Whey proteins are considered as potentially important components of a dietary solution to the obesity problem. However, the roles of individual whey proteins in energy balance remain poorly understood. This study investigated the effects of a high-fat diet (HFD) containing α-lactalbumin (LAB), a specific whey protein, or the non-whey protein casein (CAS), on energy balance, nutrient transporters expression and enteric microbial populations. C57BL/6J mice (n 8) were given an HFD containing either 20 % CAS or LAB as protein sources or a low-fat diet containing CAS for 10 weeks. HFD-LAB-fed mice showed a significant increase in cumulative energy intake (P=0·043), without differences in body weight, energy expenditure, locomotor activity, RER or subcutaneous and epididymal white adipose tissue weight. HFD-LAB intake led to a decrease in the expression of glut2 in the ileum (P=0·05) and in the fatty acid transporter cd36 (P<0·001) in both ileum and jejunum. This suggests a reduction in absorption efficiency within the small intestine in the HFD-LAB group. DNA from faecal samples was used for 16S rRNA-based assessment of intestinal microbiota populations; the genera Lactobacillus, Parabacteroides and Bifidobacterium were present in significantly higher proportions in the HFD-LAB group. These data indicate a possible functional relationship between gut microbiota, intestinal nutrient transporters and energy balance, with no impact on weight gain.

The aim of this study was to validate the estimated habitual dietary intake from a newly developed web-based FFQ (WebFFQ), for use in an adult population in Norway. In total, ninety-two individuals were recruited. Total energy expenditure (TEE) measured by doubly labelled water was used as the reference method for energy intake (EI) in a subsample of twenty-nine women, and multiple 24-h recalls (24HR) were used as the reference method for the relative validation of macronutrients and food groups in the entire sample. Absolute differences, ratios, crude and deattenuated correlations, cross-classifications, Bland–Altman plot and plots between misreporting of EI (EI–TEE) and the relative misreporting of food groups (WebFFQ–24HR) were used to assess the validity. Results showed that EI on group level was not significantly different from TEE measured by doubly labelled water (0·7 MJ/d), but ranking abilities were poor (r −0·18). The relative validation showed an overestimation for the majority of the variables using absolute intakes, especially for the food groups ‘vegetables’ and ‘fish and shellfish’, but an improved agreement between the test and reference tool was observed for energy adjusted intakes. Deattenuated correlation coefficients were between 0·22 and 0·89, and low levels of grossly misclassified individuals (0–3 %) were observed for the majority of the energy adjusted variables for macronutrients and food groups. In conclusion, energy estimates from the WebFFQ should be used with caution, but the estimated absolute intakes on group level and ranking abilities seem acceptable for macronutrients and most food groups.

Increasing evidence suggests that the source of dietary protein can have an impact on weight gain and fat mass during high-fat feeding in both humans and rodents. The present study examined whether dietary bovine serum albumin (BSA) as the dominant source of protein alters energy balance and adiposity associated with high-fat feeding. C57/BL6J mice were given a diet with 10 % of energy from fat and 20 % of energy from casein or a diet with 45 % of energy from fat and either 20 % of energy from casein (HFD) or BSA (HFD+BSA) for 13 weeks. The HFD+BSA diet did not significantly alter daily energy expenditure, locomotor activity and RER, but did increase cumulative energy intake and percentage of lean mass while reducing feed efficiency and percentage of fat mass when compared with the HFD (P< 0·05). In subcutaneous adipose tissue (SAT), the HFD+BSA diet increased the mRNA levels of PPARα (PPARA), carnitine palmitoyltransferase 1b (CPT1b) and uncoupling protein 3 (UCP3), but reduced the mRNA level of leptin when compared with the HFD (P< 0·05). The SAT mRNA levels of PPARA, CPT1b and UCP3 were negatively correlated (P< 0·05) with SAT mass, which was reduced in HFD+BSA mice compared with HFD controls (P< 0·01). No differences in epididymal fat mass existed between the groups. The HFD+BSA diet normalised plasma leptin and corticosterone levels compared with the HFD (P< 0·05). While differences in leptin levels were associated with the percentage of fat mass (P< 0·01), changes in corticosterone concentrations were independent of the percentage of fat mass (P< 0·05). The data suggest that the HFD+BSA diet influences plasma leptin levels via SAT mass reduction where mRNA levels of genes linked to β-oxidation were increased, whereas differences in plasma corticosterone levels were not related to fat mass reduction.

The present study examined the underlying mechanisms by which whey protein isolate (WPI) affects energy balance. C57BL/6J mice were fed a diet containing 10 % energy from fat, 70 % energy from carbohydrate (35 % energy from sucrose) and 20 % energy from casein or WPI for 15 weeks. Mice fed with WPI had reduced weight gain, cumulative energy intake and dark-phase VO2 compared with casein-fed mice (P< 0·05); however, WPI intake had no significant effects on body composition, meal size/number, water intake or RER. Plasma levels of insulin, TAG, leptin, glucose and glucagon-like peptide 1 remained unchanged. Notably, the intake of WPI reduced stomach weight and both length and weight of the small intestine (P< 0·05). WPI intake reduced the gastric expression of Wingless/int-1 5a (Wnt5a) (P< 0·01) and frizzled 4 (Fzd4) (P< 0·01), with no change in the expression of receptor tyrosine kinase-like orphan receptor 2 (Ror2) and LDL receptor-related protein 5 (Lrp5). In the ileum, WPI increased the mRNA expression of Wnt5a (P< 0·01) and caused a trend towards an increase in the expression of Fzd4 (P= 0·094), with no change in the expression of Ror2 and Lrp5. These genes were unresponsive in the duodenum. Among the nutrient-responsive genes, WPI specifically reduced ileal mRNA expression of peptide YY (P< 0·01) and fatty acid transporter protein 4 (P< 0·05), and decreased duodenal mRNA expression of the insulin receptor (P= 0·05), with a trend towards a decreased expression of Na–glucose co-transporter 1 (P= 0·07). The effects of WPI on gastrointestinal Wnt signalling may explain how this protein affects gastrointestinal structure and function and, in turn, energy intake and balance.

During famines females generally have a mortality advantage relative to males, and the highest levels of mortality occur in the very young and the elderly. One popular hypothesis is that the sex differential in mortality may reflect the greater body fatness combined with lower metabolism of females, which may also underpin the age-related patterns of mortality among adults. This study evaluated the ‘body fat’ hypothesis using a previously published and validated mathematical model of survival during total starvation. The model shows that at a given body weight females would indeed be expected to survive considerably longer than males in the absence of food. At a mass of 70 kg for example a female aged 30 would survive for 144 days compared with life expectancy of only 95 days for a male of the same age and weight. This effect is contributed to by both the higher body fatness and lower metabolism of the females at a given body weight. However, females are generally smaller than males and in addition to a sex effect there was also a major effect of body size – heavier individuals survive longer. When this body size effect was removed by considering survival in relation to BMI the sex effect was much reduced, and could be offset by a relatively small difference in pre-famine BMI between the sexes. Nevertheless, combining these predictions with observed mean BMIs of males and females across 48 countries at the low end of the obesity spectrum suggests that in the complete absence of food females would survive on average about 40% longer (range 6 to 64.5%) than males. The energy balance model also predicted that older adult individuals should survive much longer than younger adult individuals, by virtue of their lower resting metabolic rates and lower activity levels. Observations of the female survival advantage in multiple famines span a much wider range than the model prediction (5% to 210%). This suggests in some famines body fatness may be a significant factor influencing the mortality differential between the sexes, but in other famines other factors are likely to be more important. Moreover, the pattern of mortality in relation to age is completely opposite that predicted. These data emphasize the complex nature of famine mortality and suggest that a simple model of energy utilization alone is inadequate to explain the major aspects of this phenomenon.

During late autumn insectivorous bats must deposit a fat store to cover their energy demands throughout the period of hibernation, yet the density of aerial insects by this time has already declined from its peak in midsummer. Krzanowski (1961) suggested that bats are able to deposit a fat store by manipulating their energy expenditure; specifically by selecting cold roosting locations rather than warm roosts, and depressing their body temperatures during the day roosting period. It was hypothesized that these behavioural changes result in very low daily energy demands, and despite reduced food intake the animals are still able to gain body fat. We made several tests of this hypodiesis. First, we explored the thermo-selection behaviour of long-eared bats (Plecotus auritus) in the summer and in the pre-hibernal period. We found that in summer bats preferred temperatures of about 32–35° (about thermoneutral), but in the pre-hibernal period they preferred much colder temperatures of about 10°. Second, using open-flow respirometry we found that in the cold pre-hibernal bats entered torpor for an average of 14 h each day. Compared with bats held at 30° (that did not go torpid), the bats at 7° expended less energy. The extent of saving was sufficient to positively affect their mass balance, despite the fact that bats at lower temperature also had reduced digestive efficiencies. Our findings support the hypothesis that during the pre-hibernal period insectivorous bats manipulate their mass balance primarily by alterations in their energy expenditure, specifically utilizing energy-sparing mechanisms such as torpor.

Adipose tissue produces signals that can have a profound effect on many physiological functions, including energy expenditure and food intake. The hypothesis that variation in food intake of sheep resulting from differences in animal fatness can be predicted from effects of animal fatness on energetic efficiency was subjected to three tests. First, an existing food intake model was adapted to account for effects of animal fatness, as estimated by condition score, on food intake. Parameter values were derived from data obtained with two of five treatment groups of an experiment where ewe lambs were fed either chopped hay or pelleted concentrates. The model predicted the intake of the remaining three treatment groups satisfactorily. The energy intake model was subsequently extended with a protein module based upon a Gompertz curve to simulate changes in body weight and condition score. The model predicted these changes satisfactorily for most treatment groups during the experimental period of 50 weeks. In a last test, the final body weights and body lipid contents of animals fed either hay or concentrates for a period of 3 years were predicted. The predictions for final body weight (77 or 118 kg) and lipid content in the empty body (26 or 58 %) were within the range of expectations for sheep with access to hay or concentrates, respectively. The biological implications of the hypothesis that body fatness acts upon voluntary intake via its effects on energetic efficiency are discussed.

It is widely believed that body fatness (and hence total body mass) is regulated by a lipostatic feedback system. This system is suggested to involve at least one peripheral signalling compound, which signals to the brain the current size of body fat stores. In the brain the level of the signal is compared with a desirable target level, and food intake and energy expenditure are then regulated to effect changes in the size of body fat stores. There is considerable support for this theory at several different levels of investigation. Patterns of body-mass change in subjects forced into energy imbalance seem to demonstrate homeostasis, and long-term changes in body mass are minor compared with the potential changes that might result from energy imbalance. Molecular studies of signalling compounds have suggested a putative lipostatic signal (leptin) and a complex network of downstream processing events in the brain, polymorphisms of which lead to disruption of body-mass regulation. This network of neuropeptides provides a rich seam of potential pharmaceutical targets for the control of obesity. Despite this consistent explanation for the observed phenomena at several different levels of enquiry, there are alternative explanations. In the present paper we explore the possibility that the existence of lipostatic regulation of body fatness is an illusion generated by the links between body mass and energy expenditure and responses to energy imbalance that are independent of body mass. Using computer-based models of temporal patterns in energy balance we show that common patterns of change in body mass following perturbation can be adequately explained by this ‘non-lipostatic’ model. This model has some important implications for the interpretations that we place on the molecular events in the brain, and ultimately in the search for pharmaceutical agents for alleviation of obesity.

The direct effects of physical activity interventions on energy expenditure are relatively small when placed in the context of total daily energy demands. Hence, the suggestion has been made that exercise produces energetic benefits in other components of the daily energy budget, thus generating a net effect on energy balance much greater than the direct energy cost of the exercise alone. Resting metabolic rate (RMR) is the largest component of the daily energy budget in most human societies and, therefore, any increases in RMR in response to exercise interventions are potentially of great importance. Animal studies have generally shown that single exercise events and longer-term training produce increases in RMR. This effect is observed in longer-term interventions despite parallel decreases in body mass and fat mass. Flight is an exception, as both single flights and long-term flight training induce reductions in RMR. Studies in animals that measure the effect of voluntary exercise regimens on RMR are less commonly performed and do not show the same response as that to forced exercise. In particular, they indicate that exercise does not induce elevations in RMR. Many studies of human subjects indicate a short-term elevation in RMR in response to single exercise events (generally termed the excess post-exercise O2 consumption; EPOC). This EPOC appears to have two phases, one lasting 2 h and a smaller much more prolonged effect lasting up to 48 h. Many studies have shown that long-term training increases RMR, but many other studies have failed to find such effects. Data concerning long-term effects of training are potentially confounded by some studies not leaving sufficient time after the last exercise bout for the termination of the long-term EPOC. Long-term effects of training include increases in RMR due to increases in lean muscle mass. Extreme interventions, however, may induce reductions in RMR, in spite of the increased lean tissue mass, similar to the changes observed in animals in response to flight.

Bats seldom soar because it is behaviour generally associated with the use of thermals, which are normally of insufficient strength at night to support the behaviour. Daylight flying bats, however, such as the Samoan flying fox Pteropus samoensis may be able to exploit thermals for soaring. This may give the bats one of two advantages. It may reduce the energy costs of transport because gliding flight is much cheaper than active flapping flight. However, because less endogenous heat is generated by soaring, a second advantage may be that it reduces the thermal stress placed on these bats. Thermal stress is a factor that we have shown previously probably constrains the daylight flying behaviour of this species. Observations of the patterns of soaring behaviour at two sites on American Samoa in March and October 1995 supported the predictions of the energy saving but not the hyperthermia avoidance hypothesis. Soaring was a common behaviour under all conditions and was used extensively when conditions did not pose a threat of hyperthermia. In March, the bats also adopted flight patterns over time that exposed them to areas of the valleys where insolation was greatest, presumably increasing their risk of hyperthermia but bringing energy saving benefits. Modelling the expected heat flows during soaring and flapping flight using an established model revealed that soaring reduced the risk of hyperthermia, when flying in the shade of clouds, because of the energy savings resulting from reduced endogenous heat production. However, when soaring in sunlight, these savings are more than offset by the increased exogenous heat uptake, because a greater proportion of the wing surface is exposed when soaring. Despite its low endogenous energy cost, soaring in sunlight is not thermally advantageous, and the behaviour of the bats reflected this fact.