J Speakman

..We also provide interpretations of the results obtained at each step. We hope that this algorithm will assist in the statistically appropriate analysis of such data, a field in which there has been much confusion and some controversy...

..The TGH is further weakened by the observation of no link between the effect size of these SNPs and their prevalence, which would be anticipated under the TGH model of selection if all the SNPs had arisen in the last 900,000 years...

..We discuss two additional models--the general intake model and the dual intervention point model--that address this issue and might offer better ways to understand how body fatness is controlled...

..For some, we do not even know whether they are compensatory or obligatory. For almost all of them, we have no idea of exact mechanisms or how these costs translate into fitness trade-offs...

..These new ideas concerning the manner in which mitochondria generate free radicals as a function of metabolism shed some light on the complexity of observations linking body size, metabolism and lifespan...

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..At this level there is very little support for the suggestion that variation in RMRt (and thus BMR) is sustained by associations with SusMR...

..Together, these alternatives, based on central notion that genetic drift rather than positive selection was a dominant factor, may be called the 'drifty gene' hypothesis...

..However, those studies all used body mass index or skinfold thicknesses to measure obesity and did not always account for potential confounding factors...

..These data strongly support the previous suggestion that for small mammals single-pool models provide more accurate estimates of energy demands than two-pool formulation of the DLW method...

..Because this novel hypothesis involves random drift, rather than directed selection, it explains why, even in Western society, most people are not obese...

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..Current evidence with respect to these hypotheses is also reviewed. The limited evidence presently available does not unambiguously support any one of them...

..However, what is unclear from animal studies is whether taking drugs that suppress appetite will generate the same impact on longevity or whether the neuroendocrine correlates of hunger play an integral role in mediating CRs effects...

..Over the 40 or so years since Neel proposed the thrifty gene hypothesis, no convincing candidates for these genes have been discovered. My analysis suggests that perhaps it is time to call off the search...

..Individuals with high metabolism were therefore more uncoupled, had greater resting and total daily energy expenditures and survived longest - supporting the 'uncoupling to survive' hypothesis...

..Our aim was to use data on the scaling of daily energy expenditure, fat and lean tissue mass to predict the pattern of variation in mortality with obesity under the contrasting hypotheses...

..Reduction of insulin levels in obesity as a strategy to reduce cancer risk may pose additional problems unless it is combined also with interventions that aim to limit nutrient influx...

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..Moreover, these previous validation studies have ground up entire carcasses prior to chemical analysis, thus potentially obscuring sources of error in the DXA analysis...

..This review reveals that there might be contrasting effects of resting and nonresting energy expenditure on aging, with increases in the former being protective and increases in the latter being harmful...

..Moreover, even if such drugs are developed how the current licensing system for drug use in western societies would cope with them may be a further obstacle to their use...

..The HDL theory provides a novel mechanism underpinning the evolution of life history and ageing in endotherms, and makes a number of testable predictions that directly contrast with the predictions arising from the DST...

..Combined, these findings raise fundamental questions over whether the free-radical damage theory remains useful for understanding the ageing process, and variation in lifespan and life histories...

..5 MJ for the "at risk" AT and AA genotypes, respectively. Adjusting intake for BMR did not remove the significance (P = 0.043). FTO genotype probably affects obesity via effects on food intake rather than energy expenditure...

..In the 15 minutes it will take you to read this article nine people in the USA, and one person in the UK, will have died as a direct consequence of obesity related illnesses.'..

..The Fto(-/-) mice showed no significant differences in food intake relative to wild-types litter-mates but had an elevated metabolic rate. The apparent contrasting effects of the gene in humans and mice is worthy of closer investigation...

..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...

..Associations between body composition and the energy expended on basal metabolism and activity are complex and age dependent...

..These contrasting correlations suggest that metabolism is affecting life expectancy in different ways at these different levels of enquiry...

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..All studies agree that variation in fat-free mass (FFM) plays a major role, but effects of fat mass (FM), age, sex, and the hormones leptin, triiodothyrionine (T3), and thyroxine (T4) remain uncertain...

..Television (TV) viewing in children is associated with a higher body mass index, but it is unknown whether this reflects body fatness, and, if it does, why...

..In particular, we know nothing about how the target body weight in the brain is encoded. As our understanding in this field advances, new drug targets are likely to emerge and allow us to treat this crippling disorder...

..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...

..3. On the basis of the range of body masses of the turtles used in this study (2-60 kg), the intraspecific scaling exponent for VO2 was 0.353...

..We hypothesized that MLs might, therefore, be more likely to increase their body and fat mass when exposed to a high-fat diet (HFD)...

..We examined the compensatory responses of mice to a 20% dietary restriction...

..The literature is divided over whether variation in resting metabolic rate (RMR) is related to subsequent obesity. We set out to see whether the effect of RMR on weight gain in mice could be revealed with high-fat feeding...

..This protection may be a very important factor in sustaining uncoupled respiration, which underpins nonshivering thermogenesis at cold temperatures...

..The consequences of mass loss in females may be more significant as this may delay the onset of breeding or reduce the size or number of young, thereby negatively affecting breeding success...

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..The reduced leptin levels may drive the gorging behaviour...

..However, these signaling pathways now require further investigation to establish their exact role in life span extension following alpha-tocopherol supplementation...

..The results from our models are discussed in light of published data. Resource acquisition is shown to be a potentially important mechanism for controlling somatic damage which deserves further study...

..There was no evidence of any significant increase in any oxidative stress parameter in running individuals, despite having significantly elevated energy expenditures compared to sedentary controls...

..Our data suggest that by varying circulation of the front flippers, turtles are capable of either transporting heat quickly into the body or retaining heat inside the body, depending on the prevailing thermal demands...

..These strain-specific differences in glucose homeostatic parameters may underlie the reported unresponsiveness of DBA/2 mice to CR. We also demonstrate delineation in the response of insulin and IGF-1 to acute CR in mice...

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..These data suggest that in captive animals physiologically mediated costs on life history do not result from increased energy expenditure and consequent elevations in oxidative stress and reduced survival...

..Long-term elevations in voluntary exercise did not result in elevations in antioxidant enzyme activities or protein synthesis rates...

..We suggest that the role of this pathway in life span extension following supplementation of vitamin E now requires further investigation...

..In this context, a high BMR may actually be disadvantageous, conflicting with the idea that high BMR may bring reproductive benefits...

..The aim of this study was to map quantitative trait loci (QTLs) associated with regional fat depots in mouse lines divergently selected for food intake corrected for body mass...

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..However, the mechanism by which these changes may be linked to alterations in digestive efficiency that underpin the changes in adiposity, or how the differences are signalled by changes in photoperiod, remains unclear...

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..To validate GE PIXImus2 DXA fat mass (FM) estimates by chemical analysis, to compare previously published correction equations with an equation from our machine, and to determine intermachine variation...

..To nutritionally analyse mean energy intake (EI) from different 3 d intervals within a 7 d recording period and to evaluate the seasonal effect on energy and nutrient intake...

..Bioenergetics can provide the simple link between climate and biogeography needed to predict the consequences of climate change...

..This study examined the repeatability of measuring resting metabolic rate (RMR) in preschool children and the effect of different calculation protocols...

..5+/-1.8 per thousand (N=6 species) after endogenous substrates were in isotopic equilibrium with exogenous substrates...

..At least part of their energy minimising strategy could involve the use of moderate heterothermy, allowing a greater proportion of daily energy expenditure to diverted to milk production...

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..We discuss the ecological and behavioral implications of making associational errors and contrast the timescale and mechanisms of our theory with those of existing theory...

..A body condition score of approximately 3.5 on a 9-point scale is normal for a trained Greyhound in racing condition...

..The biological implications of the hypothesis that body fatness acts upon voluntary intake via its effects on energetic efficiency are discussed...

..The health benefits of chronic exercise may be, at least partially, due to a reduction in mitochondrial oxidant production; however, we could not detect a significant reduction in several selected parameters of oxidative stress...

..RMR of juveniles showed no clear seasonal patterns, but did increase with increasing mass. These data support the hypothesis that seasonal variation in RMR in female grey seals is related to the high costs of breeding...

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..This suggests that variation in wintering body mass between sites was due to variation in food quality/availability and not adjustments in foraging activity to varying risks of predation...

..Pups that receive greater maternal provisioning and lay down more protein may have increased survival chances at sea. This study highlights the importance of protein reserves in first year survival of grey seal pups...

..We suggest that physiological plasticity in energy expenditure, which exists both temporally and spatially, combined with stable WTO, perhaps reflecting a xeric ancestry, has enabled A. cahirinus to invade a wide range of habitats...

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..Our findings demonstrate a critical role for IRS2 in beta cell and hypothalamic function and provide insights into the role of RIPCre neurons, a distinct hypothalamic neuronal population, in growth and energy homeostasis...

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..This result suggests that senescence acceleration by increased reproductive effort is at least in part mediated by oxidative stress...

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..A similar trend was seen for male rats fed on the obesogenic diet. Thus leptin levels during pregnancy and lactation can affect the development of energy balance regulatory systems in their offspring...