Higher Body Fat Content Research Articles

Influence of body composition on the accuracy of reported energy intake in children.

Mis-reporting dietary intake is a substantial barrier to understanding the role of dietary behavior in disease. Work with adults indicates that heavier individuals under-report dietary intake and that under-reporting may be macronutrient-specific. Whether weight status and macronutrient intake influence the accuracy of dietary reports among children, however, is less clear. This research evaluated children's dietary reporting accuracy as a function of their relative weight, body composition, and macronutrient intake. Participants included 146 4- to 11-year-old children. Reported energy intake was determined by interviewing children in the presence of parents, using three multiple pass, 24-hour recalls. Children were classified as having had an under-reported, accurately reported, or over-reported dietary intake relative to total energy expenditure, as measured by doubly labeled water. Reporting accuracy was examined as a function of children's body weight, body composition (using dual energy x-ray absorptiometry), and macronutrient intake. Average reported intake was, on average, 14% greater than children's estimated expenditure (p < 0.01). Reporting accuracy varied as a function of children's relative weight and body composition; under-reporting tended to occur among heavier children, having the highest body fat content (p < 0.0001) and relative weight (p < 0.0001). These findings suggest that weight status influences the accuracy of dietary reports made by children and their parents. More research is needed to address possible psychological and social factors that introduce bias in reporting children's dietary data.

Obesity: burdens of illness and strategies for prevention or management.

Obesity is a progressive disease of unwanted fat accumulation which has multiple, organ-specific pathological consequences. The manifestations of obesity occur within virtually every subspecialty of medicine or surgery and they interact importantly to accelerate the ageing process in many organs. Many of the hazards of obesity have multiple causes (e.g., diabetes, heart disease, stroke, colonic and breast cancer, urinary incontinence, tiredness, back pain, breathlessness). All of these conditions become more prevalent with age and are also more prevalent among overweight persons, particularly those with a central fat distribution marked by a high waist circumference. Hypertension may be caused or aggravated by weight gain. It is mediated by the physical demands of an expanded circulating volume and increased metabolic rate by metabolic mechanisms related to central fat distribution and the "metabolic syndrome", and to increased sodium consumption by overweight people (because they need more food to maintain a higher metabolic rate). Since body mass index (BMI) and waist circumference increase significantly with age there is an escalation of the burden of ill health from obesity with age. The best simple indicator of disease risk with obesity is the waist circumference since this identifies people who have a high body fat content and also those who have an increased intraabdominal accumulation of fat. The quantitative burden of ill health from overweight and obesity varies within different specialties, but up to 80% of type 2 diabetes or polycystic ovarian syndrome can be attributed to obesity. Obesity is the cause of sleep apnea syndrome in around 50% of cases and heart disease in perhaps 10-20% of cases. In Scotland 80% of people with existing cardiovascular disease are overweight compared with 57% of the general population. The financial burden to health services from overweight and obesity has been incompletely assessed, although it is estimated that around 4% of total health care budgets are attributable to people having BMI > 25 kg/m(2). This is similar to the entire cost of diabetes, epilepsy or major cancers. Obesity is therefore an extremely expensive disease based on these conservative estimates from limited evaluations. More general assessments show how obesity increases the amount of time taken off work, the number of drugs prescribed and the expenditure from social services support. Thus, obesity represents a huge burden not only on the individual patient physically, psychologically, socially and financially but also on families and careers and is a huge drain on health care resources. Overweight affects well over half of all adults worldwide, progressing to BMI > 30 kg/m(2) in around 20% outside subsistence rural communities. Its rapidly increasing prevalence now described as an epidemic demands major preventive measures, as well as better medical treatment for individuals affected.

Effects of dietary lipid composition on growth, food utilization and body composition of European eel (Anguilla anguilla)

Abstract Six experimental diets with similar contents of macronutrients (450, 300 and 70 g/kg dry matter of protein, carbohydrate and fat, respectively) and, therefore, total energy, hut differing in the composition of lipid component, were each given to three replicate groups of European eel. Different fat mixtures were used to formulate diets with different levels of fatty acids considered as essential for fish: linoleic (18: 2n6), linolenic (18: ЗпЗ) and highly unsaturated fatty acid (HUFA)n3, mainly EPA (20: 5n3) and DHA (22: 6n3). One tested diet contained low levels of all the three components, three diets had a high level of each one of these, the fifth diet contained high levels of both 18C fatty acids and, finally, a sixth diet incorporated simultaneously high amounts of 18: 2n6 and (HUFA)nЗ. Dietary lipid composition did not significantly affect food intake or protein and fat apparent digestibility. However, growth and food efficiency were the best with the diet containing approximately 5 g/kg of both linoleic and linolenic acids. Although all groups increased their body fat content over the experiment, the fatty acid composition of total muscle lipids was rather insensitive to lipid dietary composition, perhaps due to the high body fat content of the eels prior to the experiment.

Effects of food restriction on food avoidance and risk of acute poisoning of captive feral pigeons from fonofos-treated seeds

Fonofos is a highly toxic insecticide to birds that, when used as a cereal seed treatment, has caused mortality of free-living feral pigeons (Columba livia). Pigeons kept individually under ad libitum feeding conditions in the laboratory do not suffer lethal poisoning because they develop a strong avoidance response to fonofos-treated seed, which restricts consumption to below lethal levels. Two laboratory experiments were conducted to assess the role of avoidance in reducing the risk of acute poisoning of captive birds under food stress. In the first experiment, pigeons acclimatized to feed on untreated wheat seeds for 6 h/day were presented with fonofos-treated seeds for 6 h on a testing day, following normal food surplus in one experimental group (eight birds) and 6 days of deprivation in another (eight birds). In the second experiment, different pigeons were acclimatized to a feeding regime of 2 h/day and treated seeds were offered without previous restriction (eight birds) or after 6 days of food restriction in which birds were given 15% of normal intake (eight birds). In the second experiment, six birds in each experimental group were videotaped to study their feeding behavior. Survivors at the end of the testing day were killed, and all birds were dissected and analyzed to determine carcass and pectoral muscle composition. Food-stressed birds lost approximately 11% of their initial body weight during 6 days of total or partial food restriction, but they still had visible fat deposits and a high body fat content, indicating that they were in good body condition in terms of energy reserves. Consumption of treated seeds on the testing day was reduced in comparison with normal intake of untreated seed in all birds, but there were differences between experimental groups. In ad libitum-fed birds, consumption of treated seed in each experiment averaged 12% and 19% of normal levels, exposure to fonofos was below lethal levels, and no bird died. In food-stressed birds, consumption was higher (34% or 56% of normal levels for the first and second experiments, respectively) and led to the ingestion of seed containing lethal doses of pesticide. Two birds in the first experiment and three in the second died of acute poisoning within around 2 h of initial exposure. The avoidance response developed quickly in both ad libitum-fed and food-stressed birds. Feeding took place in most birds almost exclusively in the first 9 min of the testing day. Within this interval, birds of the two experimental groups stopped ingesting treated seeds around 6 min after the onset of feeding. The differences between experimental groups in consumption of treated seed were due to the higher feeding rate and effective feeding time in food-stressed birds. It is concluded that although feral pigeons under severe food stress develop an early and strong conditioned food aversion to fonofos-treated seeds, avoidance does not always prevent mortality. The need for including hunger stress as a factor in avian dietary toxicity tests to make testing conditions more representative of those experienced by wild birds is discussed. http://link.springer-ny. com/link/service/journals/00244/bibs/37n1p115.html

Chronic energy deficiency and relative abdominal overfatness coexist in free‐living elderly individuals in Ho Chi Minh City, Vietnam

As part of the Cross-Cultural Research on Nutrition of Older Subjects (CRONOS) project, the aim of this cross-sectional study was to observe the nutritional status and body composition of free-living elderly and middle-aged people in a low-income area of Ho Chi Minh City, Vietnam. Anthropometric data (weight; height; arm span; four skinfold thicknesses; left upper mid-arm, abdomen, hip and calf circumferences) were collected from 50 Vietnamese men and 50 Vietnamese women aged between 35 and 44 years and 50 men and 50 women aged between 60 and 74 years who lived in Village 2, District 4, Ho Chi Minh City. The prevalence of chronic energy deficiency (CED) in the elderly men (BMI = 19.9 ± 2.8 kg/m2) was higher (52 vs 34%) than that in the middle-aged men (BMI = 19.2 ± 3.4 kg/m2). Fat-free mass and calf circumference of the elderly were lower than those of the middle-aged (p<0.001). However, the Vietnamese elderly had higher body fat content, higher abdomen-to-hip ratios and lower fat-free mass than their younger counterparts (p<0.05). In particular, 36% of middle-aged women and 20% of elderly women were classified with 'relative abdominal overfatness'. Vietnamese middle-aged and older adults are shorter and thinner than their counterparts in American and European countries but overfatness increases with age, particularly in women. Urban elderly are vulnerable to both undernutrition and overnutrition, both of which merit consideration in the geriatric care system in Vietnam.

Plasma leptin values in relation to bone mass and density and to dynamic biochemical markers of bone resorption and formation in postmenopausal women.

After the menopause it has been noted that heavier women conserve bone better than those with lower body weight. The protective effect of obesity on bone mass has been ascribed to a high body fat content. The present study of 54 postmenopausal women was undertaken to determine whether circulating plasma levels of leptin, the newly described hormone produced in adipocytes, were correlated with age-adjusted total body bone mineral content (BMC) or bone mineral density (BMD), or with dynamic biochemical markers of bone resorption or of bone formation. Leptin values were strongly correlated with all measures of adiposity (P < 0.001). Age-adjusted values for BMC and BMD, respectively, were also positively correlated (P < 0.001) with body weight (r = 0.643, r = 0.502), total fat mass (r = 0.557, r = 0.510) and with plasma leptin concentrations (r = 0.480, r = 0.551), confirming a positive relationship between fat mass and bone mass. By contrast, no significant correlations were observed between plasma leptin and dynamic markers of bone resorption (urinary deoxypyridinoline/creatinine r = -0.105, hydroxyproline/creatinine r = -0.193) or formation (plasma osteocalcin r = 0.103). Because there was no evidence for an association between ciculating plasma levels of leptin and biochemical markers of either osteoclastic or osteoblastic activity we conclude it is unlikely that circulating leptin plays any significant direct role in controlling bone cell activity. Our results do not support the hypothesis that leptin mediates the bone-sparing effects of obesity.

Whole Body Protein Metabolism Estimated by 15N Tracer Experiments and Body Composition of Mice Selected for Different Growth Parameters

Whole body protein synthesis was investigated in growing male mice which were long-time selected for high carcass protein amount (DU-6P, protein line) or for high body weight (DU-6, growth line) and in the unselected randomly bred control (DU-Ks). Six mice/line were housed singly in metabolic cages for the estimation of N balance, whole body protein synthesis (end-product method, single dose of 15N-labelled amino-acid mixture), and N distribution in the body. Another six mice/line were used for the determination of the body composition. All mice had free access to a commercial stock diet (crude protein 268 g, gross energy 19 MJ/kg dry matter) and to water. Body weight of both selection lines was about twice that of control mice at the same age. Selection for high body weight resulted in higher body fat content. Scaled to the corresponding body protein pools, the protein synthesis rates of selected mice were significantly higher than in controls, but were not significantly different between both selection lines in contrast to the protein deposition rates. The higher protein accretion in the protein line in comparison to the growth line seems to be due to a combination of a lower protein breakdown and an increased protein synthesis rate.

Adrenalectomy Lowers the Body Weight Set-Point in Rats

Gosselin, C. and M. Cabanac. Adrenalectomy lowers the body weight set-point in rats. Physiol Behav 62(3) 519–523, 1997.—In order to evaluate the impact of a complete depletion of glucocorticoids on rats’ body weight set-point, rats were adrenalectomized, and their set-points were estimated before, and after surgery. Body weight set-points were obtained from a quantitative behavioral method based on the rats’ food-hoarding response to weight deficit. In addition, body fat contents were measured in vivo using a total body electrical conductivity analyzer (TOBEC). The hoarding of food showed that adrenalectomized rats had significantly lower body weight set-points than the sham-operated controls (337 ± 11 g vs. 385 ± 8 g) and were also significantly lighter. TOBEC measurements showed that the sham-operated control rats had a higher body fat content than the adrenalectomized rats (16.7 ± 1.1% vs. 10.2 ± 1.2%). The present study demonstrates that adrenalectomy lowers the body weight set-point in rats, suggesting that the concentrations of glucocorticoid hormones, and in turn, the hypothalamic corticotrophin releasing hormone (CRH) participates in the adjustment of the body weight set-point.

Metabolic consequences of weight cycling induced by high fat and protein feedings in female Sprague-Dawley rats

In this study, we examined the effects of weight cycling (WC) on blood substrate, hormone levels and hepatic enzyme activities. WC in female Sprague-Dawley rats was produced by feeding them a high fat diet (HF) to induce obesity and then feeding them restricted amount of casein (3g/day) until body weight reached the control level. This weight gain/loss was repeated 3 times in HF ad-libitum fed rats (HFAL-C group). Rats in another group also weight cycled three times. During the refeeding phase, only 75% of the ad-lib intake of the HF diet was given to these rats (HF75-C). HFAL-NC group was fed the HF diet ad-libitum without any weight cycling. The control rats were fed the low fat rodent diet ad-lib and not cycled (CHAL-NC). After 61 weeks on these feeding regimens, all rats were sacrificed in a non-fasting state. It was observed that WC did not reduce final body weight or total fat content, but it reduced fat free mass compared to noncycled rats. The reduction of HF feeding to 75% reduced body weight of the HF75-C group to the level of the control rats. However, these rats still had a higher body fat content than the CHAL-NC group. Blood glucose and cholesterol levels were not different among the 4 groups. HF feeding significantly elevated blood insulin levels in HF groups, regardless of WC or not. Blood triglyceride levels, on the other hand, were affected by the quantity of energy consumed, rather than by the dietary fat content. Hepatic enzyme activities were not affected by WC or HF feeding. We concluded that WC exerted more influence on body composition than on metabolic parameters in Sprague-Dawley rats.

Dissociation of serum leptin concentration and body fat content during long term dietary intervention in obese individuals.

High serum leptin concentrations are observed in humans with high body fat content, indicating leptin resistance. Reducing leptin levels by lowering body fat could restore leptin sensitivity. Our study was designed to clarify the relationship between changes in body composition and circulating leptin during a long term hypocaloric diet. 12 obese women and 10 obese men were included in a 1000 kcal/day dietary intervention trial for 10 weeks. Body composition was measured by body impedance analysis and leptin by radioimmunoassay every 2 weeks. Body fat was reduced in females from 39.0 +/- 1.5 kg to 32.9 +/- 1.5 kg (p <0.001) and in males from 30.4 1.4 kg to 26.3 +/- 1.3 kg (p < 0.005). Plasma leptin decreased in females from 38.07 +/- 4.17 ng/ml to 18.90 +/- 2.75 ng/ml (p < 0.001) and in males from 10.58 +/- 2.16 ng/ml to 6.33 +/- 1.25 ng/ml (p < 0.001). Non-linear regression analysis of leptin kinetics showed a comparable one-phase exponential decline (y = Span x e(-K x x) + Plateau) in females (x +/- SEM: K = 0.48 +/- 0.01) and males (K = 0.60 +/- 0.01). Kinetics of body fat differed significantly from leptin data for females (K = 0.10 +/- 0.001, p < 0.001) but not for males (K = 0.27 +/- 0.02, p > 0.05). The leptin plateau was reached in both groups after 6- 8 weeks and the fat plateau in men after 10 weeks. Compared to healthy controls, some obese individuals had higher absolute values of leptin, but seemed to have a relative leptin deficiency when leptin was adjusted to body mass index according to a non-linear regression model of a large group of healthy women (n = 561) and men (n = 393). We conclude that during a long-term hypocaloric diet leptin uncouples from changes in body fat mass.

Decreased ratio of fat to carbohydrate oxidation with increasing age in Pima Indians.

Some metabolic changes related to age may increase the prevalence of obesity. Previous studies have shown that a low relative metabolic rate and a low ratio of fat to carbohydrate utilization are predictors of body weight gain. However, a possible relationship between age and energy substrate utilization (respiratory quotient; RQ = VCO2/VO2) has not been reported. To determine whether RQ increases and therefore fat oxidation decreases with age in Pima Indian men, independent of body fat and energy balance. We analyzed longitudinal data collected in seven non-diabetic Pima Indian men (31 +/- 6 years, 167 +/- 8 cm, 111.0 +/- 23.7 kg and 41 +/- 9% fat at baseline) who had repeated measurements of 24-hour RQ 7 years apart. On both admissions, subjects were fed a weight maintenance diet (50% carbohydrate, 30% fat and 20% protein) for 3 days before spending 1 day within a respiratory chamber for measurements of 24-hour energy expenditure, basal metabolic rate, sleeping metabolic rate and 24-hour RQ. Paired t-test was used to determine differences between the first and last measurement of 24-hour RQ. Cross-sectional data in 131 Pima Indian men (28 +/- 9 years, 171 +/- 6 cm, 94.5 +/- 24.4 kg, and 32 +/- 9% fat) were also analyzed to determine the relationship between 24-hour RQ and age. Multiple regression analysis was used to adjust 24-hour RQ for differences in energy balance (intake/expenditure in %) and percent body fat and metabolic rate for differences in body size and composition. Over a 7-year period, mean unadjusted and adjusted 24-hour RQ increased (p < 0.01). Cross-sectional data analysis showed that both the unadjusted (r = 0.19, p < 0.03) and adjusted (r = 0.19, p < 0.03) 24-hour RQ correlated with increasing age while adjusted BMR (r = -0.21, p < 0.02) correlated inversely with age. Despite a higher body fat content, older individuals utilize less fat than their younger counterparts. Reduced fat utilization and decreased BMR with age may both contribute to increasing obesity in older individuals.

Zinc supplementation aggravates body fat accumulation in genetically obese mice and dietary-obese mice

A perturbation of zinc metabolism has been noted in numerous laboratory animals with diabetes and obesity. The effects of zinc supplementation on body fat deposition in two types of experimental obese mice: genetically obese (ob/ob) mice and high-fat diet-induced ICR obese (HF) mice were investigated in this study. Their lean controls were +/? mice, and ICR on basal diet, respectively. The mice in the zinc-supplemented groups were administered 200 mg/kg zinc in their diets for 6 wk. Both the ob/ob mice and the HF mice, that were fed a diet containing a marginal zinc dosage (4-6 mg/kg), had lower zinc levels in their serum and carcass, and higher body fat content than their respective lean controls (p < 0.01). After zinc supplementation, ob/ob mice and the HF mice significantly (p < 0.05) increased their body fat by 49.4% and 18.9%, respectively. This study revealed that body fat deposition can be aggravated by zinc supplementation in both types of obese mice. Zinc may be associated with the energy homeostasis of obesity, via its interaction with dietary fat consumption.

The effect of dietary fat inclusion on growth, carcass characteristics, and chemical composition of rabbits.

Two hundred ten Californian x New Zealand White rabbits were used to study the influence of diet and slaughter weight (2.0, 2.25, and 2.5 kg) on feed intake, growth, feed efficiency, carcass characteristics, and body chemical composition. Seven diets were formulated to contain 24% ADF: Diet C (control) had no added fat; Diets T, O, and S contained 3% of added beef tallow, oleins, and soybean oil, respectively; Diets TWS, OWS, and SWS contained the same level and types of fat plus 18% heated whole soybeans (WS) to increase the dietary fat by 3%. Fat addition did not affect ADG or dressing percentage, but it improved feed:gain ratio (.06 for each 1% of dietary fat, P < .001). Although the main measurements of carcass were not influenced by fat addition, the rabbits fed diets containing the highest fat percentage had the highest weights of perirenal (P < .001) and scapular (P < .01) depots and the highest body fat content (P < .01). The increase in slaughter weight improved all the desirable carcass characteristics measured but imparied feed:gain (by 13%, P < .001). Increasing slaughter weight also increased the perirenal and scapular fat depots by 40 an 24%, respectively (P < .001)< and the body fat content by 28% (P < .01). There were no differences in the utilization of animal and vegetable fats, and only for some traits ADG, feed intake, kidney weights) did the diets with soybean oil result in better responses than those with oleins. The results indicate that fat addition to fibrous diets extends the rabbit's growing period without impairing the feed:gain ratio. The joints of rabbits killed at heavier weights have more desirable weights for marketing the carcass on a retail cut basis.

Body composition, body fat distribution, and resting metabolic rate in healthy centenarians

Our study investigated body composition and body fat distribution in healthy centenarians. Body composition, body fat distribution, and resting metabolic rate (RMR) were studied in 40 adult subjects aged < 50 y, 35 aged subjects > 75 y, and 15 healthy centenarians aged > 100 y. Body composition was determined by bioimpedance analysis, body fat distribution was calculated as waist-hip ratio (WHR), and RMR was calculated by using the Arciero-Poehlman formula. Healthy centenarians had a cognitive impairment and degree of disability greater than aged subjects. Despite such differences, fat-free mass (FFM) and RMR were not different in centenarians compared with aged subjects but were lower than in adult subjects. In contrast, healthy centenarians had a WHR lower than that of aged subjects but not different from that of the adult subjects. After the level of physical activity and degree of disability were adjusted for, FFM (44 +/- 2.7 and 40 +/- 1.1 kg; P < 0.05) and RMR (6757 +/- 761 and 5891 +/- 723 kJ/24 h; P < 0.05) were significantly higher in healthy centenarians than in aged subjects, respectively. Independent of age, sex, body weight, degree of disability, level of physical activity, and fasting plasma triiodothyronine, there was a strong correlation between RMR and FFM (r = 0.50, P < 0.05) in healthy centenarians. In conclusion, healthy centenarians had a lower FFM and higher body fat content than aged subjects. Level of physical activity and degree of disability seem to be the major determinants for explaining such differences.

The Maastricht protocol for the measurement of body composition and energy expenditure with labeled water.

An update of practical aspects of the use of labeled water for the measurement of total body water (TBW) and energy expenditure (EE) is presented as applied in Maastricht, The Netherlands. We use a 10-hour equilibration period. The isotopes for the measurement of TBW and EE are routinely administered, after collecting a background urine sample, as a last consumption before the night. Our data show an underestimate of TBW measured with isotope dilution after 4 hours (in the morning), a discrepancy which increases with the size of TBW. No such relation and no significant differences were found after 10-hour (overnight) equilibration. The ratio between the dilution space for deuterium and oxygen-18 is higher than the earlier figure of 1.03, especially in adult subjects with a high body fat content. For an observation period of EE over two weeks, samples from the second and the last voiding on the first, mid, and last day of the observation period are collected. Differences in EE calculated from morning and evening samples within the first and second week allow detection of sampling errors and if so, samples are excluded from the final calculation. Differences of EE between weeks 1 and 2 allow a check for the consistency of the subjects' physical activity level and usually fall within 10% of the average EE over the total observation interval.

Glucoprivation induces anestrus and lipoprivation may induce hibernation in Syrian hamsters.

Previous results supported the notion that estrous cycles in Syrian hamsters are responsive to the general availability of metabolic fuels, rather than to either fatty acid or glucose availability per se. To test this idea, we monitored estrous cycles in hamsters that were fed ad libitum and treated with a range of doses of 2-deoxy-D-glucose (2-DG), an inhibitor of glucose utilization. Hamsters treated with 2-DG at doses ranging from 750-1,250 mg/kg showed normal estrous cycles, but higher doses (1,750 or 2,000 mg/kg) induced anestrus. While it is clear from these data that estrous cycles are affected by glucoprivation, it is not clear whether they are responsive to decreased fatty acid availability. Groups of hamsters were fed ad libitum and treated with a range of doses of methyl palmoxirate (MP), an inhibitor of fatty acid utilization. Some of the hamsters that received the highest doses became torpid and thus were not tested for lordosis. None of the euthermic, MP-treated hamsters became anestrous. Other experiments examined the role of glucose availability in fasted hamsters. Hamsters with a high body fat content were protected from fasting-induced anestrus. In contrast, fat food-deprived hamsters treated with low doses of 2-DG (750 mg/kg) became anestrous. Thus fatty acids mobilized from adipose tissue did not prevent fasting-induced anestrus when glucose utilization was blocked. One interpretation is that during fasting fatty acid utilization spares glucose for other tissues involved in the control of estrous cycles.(ABSTRACT TRUNCATED AT 250 WORDS)

Seasonal changes in density, demography and body composition of small mammals in a southern temperate forest

Eleven small mammal species (nine rodents and two shrews) were recorded in 16 months of trapping in the Karkloof Forest, Natal. Total densities varied seasonally, ranging from 60.7 animals/ha in the dry autumn and winter to 29.1 animals/ha at the onset of the rains in spring and early summer. Peaks in breeding coincided with high body fat and water content in the five common species during summer: in winter, when body fat and water levels were low, there was no breeding. This may be related to poor food quality at this time. Annual changes in density, breeding season and juvenile recruitment of Rhabdomys pumilio, Mastomys natalensis and Myosorex varius are the same as recorded in conspecific populations from other habitat types and do not seem modified by the habitat stability of the forest environment. Of the five common species, only Grammomys dolichurus, one of the few forest‐associated small mammals in southern Africa, and Graphiurus murinus demonstrated stable, K‐selectéd life‐history styles.

The Pathophysiology of Obesity

Effective therapy for obesity would result in an improved quality of life and possibly even an increased life expectancy for many individuals. To understand why current therapy for obesity is inadequate, it is necessary to review what is known about the regulation of body composition. In individuals of normal weight, energy balance is maintained at a body fat content of less than 25% by adjustments in both energy intake and energy expenditure. Obese individuals are able to achieve long-term energy balance only at a higher body fat content. Both obese and normal weight individuals respond to any deviation of body fat content from its customary value with counterregulatory changes in energy expenditure and appetite. This review will elaborate upon these observations both to explain the limitations of current weight loss therapy and to suggest a strategy for targeting available therapy until the physiology of energy balance is better understood.

The influence of rumen volatile fatty acids on protein metabolism in growing lambs.

The effect of acetic or propionic acid rumen fermentation patterns on whole-body protein turnover, tissue protein synthetic rates and body composition was investigated in growing lambs. Protein turnover was assessed using a continuous intravenous infusion of [2,3-3H]tyrosine and tissue protein fractional synthetic rates (FSR) from the specific activities of plasma free, intracellular free and tissue bound tyrosine. Only the FSR of muscle tissue approached significance. The high FSR in the propionic group was attributed to the high plasma insulin concentration. Values for whole-body protein synthesis, corrected for tyrosine oxidation, were similar to those obtained by summating protein synthesis in individual tissues, confirming that tyrosine oxidation should be measured accurately if reliable whole-body protein synthesis values are required. Tyrosine oxidation and flux were high in the acetic acid group, suggesting that amino acids are used for gluconeogenesis. The high protein turnover rate probably ensures an adequate supply of gluconeogenic amino acids and that the penalty of mobilizing body proteins for gluconeogenic amino acids is minimal. In the propionic acid group, high plasma glucose and insulin concentrations were associated with a low protein turnover rate, high ratio of deposited: synthesized protein and a high body fat content. It is concluded that changing the proportion of ruminal volatile fatty acids influences protein turnover, protein synthesis and the efficiency of protein retention. Such factors probably contribute, indirectly, to the observed differences in body composition.

A thermographic study of the effect of body composition and ambient temperature on the accuracy of mean skin temperature calculations.

The problem associated with using measurements from a small number of sites to determine mean skin temperature was investigated by studying variations in distributions of skin temperatures of the bare torsos of humans exposed to ambient temperatures of 18, 23, and 28 degrees C. Following a 60 minute equilibration period the temperatures of four regions (chest, abdomen, upper back, and lower back) were measured using both thermistors and an infra-red thermographic system. Regions of the torso usually represented by a single temperature exhibited significant point-to-point temperature variations especially in chilled subjects. Also an earlier finding was confirmed: in that larger variations in skin temperature distributions occur as body fat content increases. Caution must therefore be used in applying the concept of a mean skin temperature derived from a few select sites, especially with nude subjects who are chilled or have a high body fat content.