The evolution of human fatness and susceptibility to obesity: an ethological approach

Human susceptibility to obesity is an unusual phenomenon amongst animals. An evolutionary analysis, identifying factors favouring the capacity for fat deposition, may aid in the development of preventive public health strategies. This article considers the proximate causes, ontogeny, fitness value and evolutionary history of human fat deposition. Proximate causes include diet composition, physical activity level, feeding behaviour, endocrine and genetic factors, psychological traits, and exposure to broader environmental factors. Fat deposition peaks during late gestation and early infancy, and again during adolescence in females. As in other species, human fat stores not only buffer malnutrition, but also regulate reproduction and immune function, and are subject to sexual selection. Nevertheless, our characteristic ontogenetic pattern of fat deposition, along with relatively high fatness in adulthood, contrasts with the phenotype of other mammals occupying the tropical savannah environment in which hominids evolved. The increased value of energy stores in our species can be attributed to factors increasing either uncertainty in energy availability, or vulnerability to that uncertainty. Early hominid evolution was characterised by adaptation to a more seasonal environment, when selection would have favoured general thriftiness. The evolution of the large expensive brain in the genus Homo then favoured increased energy stores in the reproducing female, and in the offspring in early life. More recently, the introduction of agriculture has had three significant effects: exposure to regular famine; adaptation to a variety of local niches favouring population-specific adaptations; and the development of social hierarchies which predispose to differential exposure to environmental pressures. Thus, humans have persistently encountered greater energy stress than that experienced by their closest living relatives during recent evolution. The capacity to accumulate fat has therefore been a major adaptive feature of our species, but is now increasingly maladaptive in the modern environment where fluctuations in energy supply have been minimised, and productivity is dependent on mechanisation rather than physical effort. Alterations to the obesogenic environment are predicted to play a key role in reducing the prevalence of obesity.     

Characterization of obesity in Japanese monkeys (Macaca fuscata) in a pedigreed colony

BACKGROUND: Japanese monkey, Macaca fuscata, is recognized as the monkey species inhabiting the northernmost area in the world, and thus likely to possess unique fat-depositing mechanisms to resist cold weather in winter. We report that obese females are present in the Wakasa group of Japanese monkey reared in an open enclosure of the Primate Research Institute, Kyoto University. METHODS AND RESULTS: Eight of 12 females were categorized as obese, showing percentage body fat of over 22%. The levels of serum leptin (mean +/- SD, 4.9 +/- 2.3 ng/ml) measured in these obese monkeys were significantly higher than those of non-obese peers of the same group (n = 4; 1.2 +/- 0.5 ng/ml) and another Japanese monkey group (Takahama, n = 14; 0.8 +/- 0.25 ng/ml); however, serum levels of adiponectin, insulin, glucose, hemoglobin A1c, and fructosamine did not differ between obese and non-obese monkeys. Few serum lipid parameters such as triglyceride and cholesterol showed lower levels in obese monkeys than their non-obese peers. CONCLUSIONS: These results show that these obese monkeys in the Wakasa group have not developed obesity-related diseases/disorders such as diabetes. In the Wakasa group, the frequency of obese individuals was high in some maternal lineages, suggesting that genetic factors responsible for obesity may have been inherited in these lineages.     

Eider females form non-kin brood-rearing coalitions

Kin selection is a powerful tool for understanding cooperation among individuals, yet its role as the sole explanation of cooperative societies has recently been challenged on empirical grounds. These studies suggest that direct benefits of cooperation are often overlooked, and that partner choice may be a widespread mechanism of cooperation. Female eider ducks (Somateria mollissima) may rear broods alone, or they may pool their broods and share brood-rearing. Females are philopatric, and it has been suggested that colonies may largely consist of related females, which could promote interactions among relatives. Alternatively, shared brood care could be random with respect to relatedness, either because brood amalgamations are accidental and nonadaptive, or through group augmentation, assuming that the fitness of all group members increases with group size. We tested these alternatives by measuring the relatedness of co-tending eider females in enduring coalitions with microsatellite markers. Females formed enduring brood-rearing coalitions with each other at random with respect to relatedness. However, based on previous data, partner choice is nonrandom and dependent on female body condition. We discuss potential mechanisms underlying eider communal brood-rearing decisions, which may be driven by the specific ecological conditions under which sociality has evolved in this species.     

Male size does not affect the strength of male mate choice for high-quality females in Drosophila melanogaster

Theory predicts that the strength of male mate choice should vary depending on male quality when higher-quality males receive greater fitness benefits from being choosy. This pattern extends to differences in male body size, with larger males often having stronger pre- and post-copulatory preferences than smaller males. We sought to determine whether large males and small males differ in the strength (or direction) of their preference for large, high-fecundity females using the fruit fly, Drosophila melanogaster. We measured male courtship preferences and mating duration to show that male body size had no impact on the strength of male mate choice; all males, regardless of their size, had equally strong preferences for large females. To understand the selective pressures shaping male mate choice in males of different sizes, we also measured the fitness benefits associated with preferring large females for both large and small males. Male body size did not affect the benefits that males received: large and small males were equally successful at mating with large females, received the same direct fitness benefits from mating with large females, and showed similar competitive fertilization success with large females. These findings provide insight into why the strength of male mate choice was not affected by male body size in this system. Our study highlights the importance of evaluating the benefits and costs of male mate choice across multiple males to predict when differences in male mate choice should occur.     

Visceral Adipose Tissue in Women: Longitudinal Study of the Effects of Fat Gain,Time, and Race

Objective: To determine the effects of fat gain, time, and race on the accumulation of visceral adipose tissue (VAT) in a group of normal‐weight premenopausal women. Research Methods and Procedures: Sixty‐five women participated in the study (32 African American and 33 white). The mean age of subjects was 34 ± 6 years (range, 22 to 47 years). Eligible subjects were women who had body mass indices <25 kg/m² at baseline and who had completed evaluations at baseline and at follow‐up year 1, without intervention. A subset of subjects was reevaluated annually for up to 4 years. Body composition was assessed by DXA, and VAT was determined from a single computed tomography scan. A linear mixed model was used to examine changes in VAT over time, with total body fat as a covariate Results: Total fat mass was not significantly different between races at baseline and increased significantly in both groups over time (p < 0.001). Time‐related increases in total body fat were greater in African‐American women (p < 0.01). VAT was significantly higher in white women at baseline (p < 0.01) and increased significantly over time in both races (p < 0.01), but remained higher in white women (p < 0.001). Increases in VAT, relative to total body fat, were greater than the increases in total body fat over time, independent of age and race (p < 0.001). Discussion: Gaining total body‐fat mass results in a higher increase in VAT, relative to total body fat, regardless of race and age, although African‐American women maintain a lower VAT levels across time.     

Adult obesity does not predict 6-year weight gain in men: the Aerobics Center Longitudinal Study

Objective: To determine the longitudinal relation between history of adult obesity and the 6‐year trajectory of weight change in men. Research Methods and Procedures: Subjects were healthy, affluent men (n = 761) between the ages of 20 and 78 years who completed at least four comprehensive medical exams at the Cooper Clinic between 1987 and 2003. Maximum adult weight was reported, and current height was measured at baseline. Body weight and cardiorespiratory fitness were measured at all examinations. Adult obesity status was determined from self‐reported maximum weight and measured height at baseline as BMI ≥ 30 kg/m². Weight at all examinations was regressed on a history of adult obesity using linear mixed effects modeling. Results: At baseline, men reporting a history of adult obesity were significantly heavier than men reporting no such history (BMI 29.8 vs. 25.0 kg/m²; p < 0.05). However, the rate of weight gain among men with a history of obesity was slower than among men without a history of adult obesity (0.04 vs. 0.18 kg/yr; p = 0.09), although this difference was only marginally significant. Fitness modulated the relationship between history of obesity and weight change over time, and both higher levels of fitness and greater frequency of dieting were associated with attenuated weight gain. In contrast, chronic disease and depression were associated with accelerated weight gain. Discussion: Although a history of obesity was associated with higher weight, it did not seem to result in accelerated weight gain over time. Additionally, dieting and fitness were important for minimizing weight gain.     

Identification of quantitative trait loci that regulate obesity and serum lipid levels in MRL/MpJ x SJL/J inbred mice

The total body fat mass and serum concentration of total cholesterol, HDL cholesterol, and triglyceride (TG) differ between standard diet-fed female inbred mouse strains MRL/MpJ (MRL) and SJL/J (SJL) by 38-120% (P < 0.01). To investigate genetic regulation of obesity and serum lipid levels, we performed a genome-wide linkage analysis in 621 MRLx SJL F2 female mice. Fat mass was affected by two significant loci, D11Mit36 [43.7 cM, logarithm of the odds ratio (LOD) 11.2] and D16Mit51 (50.3 cM, LOD 3.9), and one suggestive locus at D7Mit44 (50 cM, LOD 2.4). TG levels were affected by two novel loci at D1Mit43 (76 cM, LOD 3.8) and D12Mit201 (26 cM, LOD 4.1), and two suggestive loci on chromosomes 5 and 17. HDL and cholesterol concentrations were influenced by significant loci on chromosomes 1, 3, 5, 7, and 17 that were in the regions identified earlier for other strains of mice, except for a suggestive locus on chromosome 14 that was specific to the MRL x SJL cross. In summary, linkage analysis in MRL x SJL F2 mice disclosed novel loci affecting TG, HDL, and fat mass, a measure of obesity. Knowledge of the genes in these quantitative trait loci will enhance our understanding of obesity and lipid metabolism.     

Comparison of body fat composition and serum adiponectin levels in diabetic obesity and non-diabetic obesity

Objective: Clinical aspects of diabetes and obesity are somewhat different, even at similar levels of insulin resistance. The purpose of this study was to determine differences in body fat distribution and serum adiponectin concentrations in diabetic and non‐diabetic obese participants. We were also interested in identifying the characteristics of insulin resistance in these two groups, particularly from the standpoint of adiponectin. Research Methods and Procedures: Adiponectin concentrations of 112 type 2 diabetic obese participants and 124 non‐diabetic obese participants were determined. Abdominal adipose tissue areas and midthigh skeletal muscle areas were measured by computed tomography. A homeostasis model assessment of the insulin resistance score was calculated to assess insulin sensitivity. The relationships among serum adiponectin, body fat distribution, and clinical characteristics were also analyzed. Results: Both abdominal subcutaneous and visceral fat areas were higher in the non‐diabetic obese group, whereas midthigh low‐density muscle area was higher in the diabetic obese group. The homeostasis model assessment of the insulin resistance score was similar between groups, whereas serum adiponectin was lower in the diabetic obese group. Abdominal visceral fat (β = ?0.381, p = 0.012) was a more important predictor of adiponectin concentration than low‐density muscle (β = ?0.218, p = 0.026) in cases of non‐diabetic obesity, whereas low‐density muscle (β = ?0.413, p = 0.013) was a better predictor of adiponectin level than abdominal visceral fat (β = ? 0.228, p = 0.044) in diabetic obese patients. Discussion: Therefore, factors involved in pathophysiology, including different serum adiponectin levels and body fat distributions, are believed to be responsible for differences in clinical characteristics, even at similar levels of insulin resistance in both diseases.     

Contribution of breast volume and weight to body fat distribution in females

Breast volume and body composition were measured in 45 adult females to determine the contribution of breast weight and breast volume to total body fat. Plaster casts were filled with sand of known density to obtain breast volume. Breast weight was computed as breast volume times its density. The correlation between total breast volume and percent body fat was r = .40. Breast weight (X = 484 grams) accounted for 3.5 percent of the total weight of body fat, and at most, 12 percent of the estimated quantities of sex-specific fat. A theoretical model is proposed for the distribution of body fat in the female which subdivides total body fat into three components: reserve storage fat, essential fat, and expendable storage fat.     

Body composition and breast cancer in postmenopausal women: a Danish prospective cohort study

Objective: To assess the importance of body fat mass (BFM) and fat free mass (FFM) for the established positive association between BMI and breast cancer among post‐menopausal women. Research Methods and Procedures: A prospective cohort of 23,788 postmenopausal women included in the Danish study Diet, Cancer, and Health during 1993 to 1997 was linked to the Danish Cancer Registry to identify all cases of breast cancer occurring during 1993 to 2002. Breast cancer incidence rate ratios for anthropometric measurements with adjustment for known risk factors for breast cancer were calculated by Cox regression analyses. Results: Among the most commonly used anthropometric measurements, BMI was positively associated with breast cancer among never users of hormone replacement therapy (HRT). By splitting BMI into two indices, BFM index and FFM index, we found that the incidence rate ratio with each 1 kg/m² among never users of HRT was 0.98 (95% confidence interval, 0.93 to 1.03) for BFM index and 1.12 (95% confidence interval, 1.00 to 1.26) for FFM index after mutual adjustment. Discussion: The finding for BMI was in accordance with previous findings. Our results indicate that the FFM component of BMI may play a role for development of breast cancer among never users of HRT.     

Estimation of Energy Expenditure from Physical Activity Measures: Determinants of Accuracy

Objective: To describe the determinants, specifically age, body mass index, percentage of body fat, and physical activity (PA) level, associated with over‐ and underestimation of energy expenditure (EE) using PA records and the Stanford Seven‐Day Physical Activity Recall (7DR) compared with doubly labeled water (DLW). Research Methods and Procedures: We collected PA measures on 24 males eating a controlled diet designed to maintain body weight, and we determined EE from DLW and estimated EE from PA records and 7DR. Results: Absolute differences in the estimation of EE between DLW and PA assessment methods were greater for the 7DR (30.6 ± 9.9%) than PA records (7.9 ± 3.2%). In PA records, overestimation of EE was greater with older age and higher body fatness; EE was overestimated by 16.7% among men 50 years and older compared with only 5.3% among men <40 years of age. For percentage of body fat, EE was overestimated by 19.7% among men with a percentage of body fat ≥30% compared with only 5.6% among men with a percentage of body fat <25%. A trend for less overestimation of EE with higher levels of PA (measured by DLW/basal metabolic rate [BMR]) also was observed in the PA records. In the 7DR, the estimates of EE varied widely and no trends were observed by age, percentage of body fat, and PA levels. Discussion: Estimation of EE from the 7DR is considerably more variable than from PA records. Factors related to age and percentage of body fat influenced the accuracy of estimated EE in the PA record. Additional studies are needed to understand factors related to accurate reporting of PA behaviors, which are used to estimate EE in free‐living adults.     

Apolipoprotein A‐II Polymorphism and Visceral Adiposity in African‐American and White Women

To determine the association between the ?265 T to C substitution in the apolipoprotein A‐II (APOA‐II) gene and levels of visceral adipose tissue (VAT) in a group of premenopausal African‐American and white women, we genotyped 237 women (115 African‐American and 122 white) for this polymorphism. Body composition was assessed by DXA, and VAT was determined from a single computed tomography scan. In addition to VAT, we examined the association between the polymorphism and other phenotypes (total body fat, total abdominal adipose tissue, and subcutaneous abdominal adipose tissue). The mutant C allele in the APOA‐II gene was less frequent in African‐American compared with white women, 23% vs. 36%, respectively (p < 0.01). VAT was significantly higher in carriers of the C allele compared with noncarriers after adjustment for total body fat (p < 0.05). When separate analyses by ethnic group were conducted, the association between the polymorphism and VAT was observed in white (p < 0.05) but not African‐American (p = 0.57) women. There was no association between the polymorphism and the other phenotypes. These results indicate a significant association between the T265C APOA‐II polymorphism and levels of VAT in premenopausal women. This association is present in white but not African‐American women.     

Regional body volumes, BMI, waist circumference, and percentage fat in severely obese adults

Objective: This study presents total body volume (TBV) and regional body volume, and their relationships with widely used body composition indices [BMI, waist circumference (WC), and percentage body fat (% fat)] in severely obese adults (BMI ≥35 kg/m²). Research Methods and Procedures: We measured TBV, trunk volume (TV), arm volume (AV), leg volume (LV), and WC and estimated % fat in 32 severely obese persons with BMI 36 to 62 kg/m² (23 women; age, 19 to 65 years; weight, 91 to 182 kg) and in 58 persons with BMI <35 kg/m² (28 women; age, 18 to 83 years; weight, 48 to 102 kg) using a newly validated 3‐day photonic image scanner (3DPS, Model C9036–02, Hamamatsu Co., Japan) and calculated TV/TBV, AV/TBV, and LV/TBV. Results: Men had significantly larger TBV and higher TV/TBV and AV/TBV, but significantly lower LV/TBV than women, independently of BMI. TV/TBV increased while AV/TBV and LV/TBV decreased with increasing BMI, WC, and % fat, and the rate of increase in TV/TBV per % fat was significantly greater in severely obese individuals than in individuals with BMI <35 kg/m². The relationships for TBV with % fat were much lower than with BMI or WC. Conclusion: Body volume gains were mainly in the trunk region in adults, irrespective of sex or BMI. For a given BMI, WC, or % fat, men had a significantly larger TV than women. The implication is that men could have higher health risks due to having higher trunk body weight as a proportion of total body weight compared with severely obese or less severely obese women.     

Media Use and Dreaming: The Relationship Among Television Viewing, Computer Game Play, and Nightmares or Pleasant Dreams.

Children (N=2,546) in a random sample of 15 secondary schools in Flanders, Belgium, completed a questionnaire about volume of television viewing, computer game playing, and nightmares and pleasant dreams related to these activities. TV content showed up frequently in nightmares for 33% of the children, and computer games were associated with nightmares in about 10% of boys and 5% of girls. About 60% of 13-year-olds and 50% of 16-year-olds reported having pleasant dreams related to TV. Computer games also appeared in pleasant dreams for a majority of 13-year-olds and a minority of 16-year-olds. Media influence on dream content was not limited to excessive media users. Concerns about the implications for the impact of media on dreams and general psychological well-being are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Association Between Body Fat Response to Exercise Training and Multilocus ADR Genotypes

Objectives : To examine the contribution of adrenergic receptor (ADR) gene polymorphisms and their gene‐gene interactions to the variability of exercise training‐induced body fat response. Research Methods and Procedures : This was an intervention study that used a volunteer sample of 70 healthy, sedentary men (n = 29) and postmenopausal women (n = 41) 50 to 75 years of age, with a BMI ≤37 kg/m², from the Washington, DC, metropolitan area. Participants completed 6 weeks of dietary stabilization (American Heart Association diet) before 24 weeks of supervised aerobic exercise training. Diet was maintained throughout the intervention. Change in percent total body fat, percent trunk fat, and fat mass by DXA in ADR genotype groups (Glu¹²/Glu⁹ α2b‐ADR, Trp64Arg β3‐ADR, and Gln27Glu β2‐ADR) at baseline and after 24 weeks of aerobic exercise training was measured. Results : In multivariate analysis (covariates: age, gender, and baseline value of phenotype), best fit models for percent total body and trunk fat response to exercise training retained main effects of all three ADR gene loci and the effects of each gene‐gene interaction (p = 0.009 and 0.003, respectively). Similarly, there was a trend for the fat mass response model (p = 0.03). The combined genetic factors explained 17.5% of the overall model variability for percent total body fat, 22% for percent trunk fat, and 10% for fat mass. Discussion : The body fat response to exercise training in older adults is associated with the combined effects of the Glu¹²/Glu⁹ α2b‐, Trp64Arg β3‐, and Gln27Glu β2‐ADR gene variants and their gene‐gene interactions.     

Expression and localization of storage protein 1 (SP1) in differentiated fat body tissues of red hairy caterpillar, Amsacta albistriga Walker

The accumulation and utilization of storage proteins are prominent events linked to the metamorphosis of holometabolous insects. The female-specific storage protein 1 (SP1) is the major storage protein found in the hemolymph and fat body of female larvae of the groundnut pest, Amsacta albistriga. Here we show SP1 expression and localization in differentiated fat body tissues using biochemical and immunohistochemistry scrutiny. Comparison of A. albistriga SP1 with that of other species with respect to amino acid composition and N-terminal sequences show that SP1 is a methonine-rich protein and its identity was confirmed by means of immunoblot analysis. Northern blot studies revealed that the SP1 gene demonstrates stage- and tissue-specific expression in the peripheral fat body cells during the mid-larval period of fifth instar of A. albistriga. During the larval pupal transformation, SP1 are sequestered mainly by the perivisceral fat body tissues, until they serve the purpose of supplying amino acids for the production of egg yolk proteins. Further, electron microscopic studies using immunogold tracer techniques confirmed the localization of crystalline SP1 reserves, stored in the perivisceral fat body tissues. Hence, the peripheral fat body is responsible for biosynthesis of storage proteins, whereas the perivisceral fat body is a specialized storage organ.     

Mating increases starvation resistance and decreases oxidative stress resistance in Drosophila melanogaster females

Mating stimulates complex physiological changes in females of Drosophila melanogaster. Long-term effects of mating are manifested in increased fecundity and shortened lifespan. It is not clear how mating affects stress resistance in fly females. We addressed this question here and found that mated and highly fecund wild-type D. melanogaster females have significantly higher resistance to starvation throughout their lifetime than age-matched virgin females. Mean survival time under starvation was age dependent with maximum survival time observed in 15-day-old mated females. Mating-induced increase in starvation resistance was associated with significantly higher fat reserves stored as triacylglycerols. While mated females had higher resistance to starvation, their resistance to oxidative stress was significantly lower than in age-matched virgins. Our study revealed that mating leads to an opposing relationship between resistance to starvation and resistance to oxidative stress in Drosophila females. Thus, shortened lifespan of mated females is associated with their high-fat content and greater susceptibility to oxidative stress.     

Dynamics of oogenesis in the tropical anuranRana tigrina (Amphibia: Ranidae) with special reference to vitellogenic cycles in wild-caught and captive flogs

The ovarian cycle ofRana tigrina was analysed by quantifying the developing oocytes (classified into stages on the basis of diameter) and atretic ones at monthly intervals. Stages I to IV represent oocytes in the first growth phase and the remaining ones the vitellogenic or second growth phase. Stages I–III occurred year round but exhibited significant variation in their number. The number of stage II oocytes always dominated the other stages. Recruitment of oocytes to stages IV and V in April marked the initiation of vitellogenic growth in all specimens. Of the 30 to 35% second growth phase oocytes, 25 to 28% reached ovulatory sizes by June. After spawning the ovarian mass declined drastically from 15 to 0.2% of body mass in July. Atresia was maximal (5%) in August. In other months, it was less than 1.5% of the total oocytes. Oogenic episodes occurred in March and July yielding new oocytes. The number of first growth phase oocytes fluctuated from 65 to 95%. The fluctuation was inversely correlated with the second growth phase oocytes indicating a 30 to 35% annual turnover rate of oocytes in the frog. The final egg number/ovarian mass is positively correlated with the snout-vent length as well as body mass of the frogs.R. tigrina produces about 4000 eggs/100g body mass. Further, the mean number of yolky eggs/100 g body mass and the total volume (V) of eggs/frog were highly correlated. Frogs living in captivity produced fewer eggs compared to the wild ones (3594 ± 227 in captivevs 4704 ± 317 in wild frogs). Also, these frogs failed to breed though they showed amplexus with breeding males. Injection of desoxycorticosterone acetate however induced spawning in 4 out of 5 frogs. They released about 3000 eggs each. Captivity seems to mainly impair breeding and to a little extent the vitellogenic growth of oocytes inR. tigrina.