Predicted effects of small decreases in energy expenditure on weight gain in adult women.

Small daily positive energy imbalances of 200 to 800 kJ (about 50 to 200 kcal) due to reduced resting energy expenditure (REE), reduced diet-induced thermogenesis, or physical inactivity are believed to predispose to obesity. However, estimates of the magnitude of the weight gain often fail to account for concurrent changes in body composition and increases in maintenance energy requirements as weight increases and energy equilibrium is re-established. Using previously reported data on body composition and REE in women and the energy cost of tissue deposition, we used mathematical models to predict the theoretical effect of a persistent reduction in energy expenditure on long-term weight gain, assuming no adaptation in energy intake. The analyses indicate the following effects of a reduced level of energy expenditure in lean and obese women: (i) REE rises more slowly with increasing degrees of obesity due to a declining proportion of the more metabolically active fat-free mass; so, for the same positive energy balance, a significantly greater weight gain is expected for obese than for lean women before energy equilibrium is re-established; (ii) due to the greater energy density of adipose tissue, the time course of weight gain to achieve energy balance is longer for obese subjects: in general, this is approximately five years for lean and ten years for obese women; (iii) the magnitude of weight gain of lean women in response to a reduced energy expenditure of 200 to 800 kJ/day is only about 3 to 15 kg, amounts insufficient to explain severe obesity.

Prevalence of normal weight obesity in the general population

Background and Aims: normal weight obesity (NWO) has been defined as an excessive body fat (BF) associated with a normal body mass index (BMI). Little is known regarding its prevalence in the general population or which cut-offs for BF should be used. Methods: convenience sample of 1,523 Portuguese adults. BF was measured by validated hand-held bioimpedance. NWO was defined as a BMI<25 kg/m2 and a %BF mass>30%, along other published criteria. Results: prevalence of NWO was 10.1% in women and 3.2% in men. In women, prevalence of NWO increased considerably with age, and virtually all women aged over 55 with a BMI<25 kg/m2 were actually considered as NWO. Using gender specific cut-offs for BF (29.1% in men and 37.2% in women) led to moderately lower of NWO in women. Using gender- and age-specific cut-points for %BF considerably decreased the prevalence of NWO in women (0.5 to 2.5% depending on the criterion) but not in men (1.9 to 3.4%). Conclusions: gender- and age- specific or at least gender-specific, instead of single cut-offs for %BF, should be used to characterize and study NWO.

Metabolic cost of growth in very low-birth-weight infants.

Forty-eight measurements of energy expenditure were performed in 15 very low-birth-weight infants during the first 6 wk of life. Their mean birth weight and gestation age was 1223 g and 31 wk respectively. Their mean weight gain was 11.2 g/kg . d (range: -6.6 to +15.9 g/kg . d.). The mean energy expenditure increased from 170 kJ/kg . d (wk 1) to 252 kJ/kg . d (wk 6). There was a significant relationship between weight gain and energy expenditure (r = 0.58, P less than 0.001) and also between the net increase in body weight gain and the net increase in energy expenditure (r = 0.80, P less than 0.001). From the slopes of these regression lines, the metabolic cost of growth was found to be approximately 2.3 kJ/g of weight gain. Carbohydrate oxidation represented 80% of energy expenditure at the second wk and decreased to 65% the 6th wk, whereas lipid oxidation during the same period increased from 14 to 30% and the relative protein oxidation remained unchanged, covering 5-6% of the energy expended.

Simple models for multi-attribute choice with many alternatives: When it does and does not pay to face tradeoffs with binary attributes

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Influence of photoperiod on body weight and depth of burrowing in larvae of Chrysomya megacephala (Fabricius) (Diptera, Calliphoridae) and implications for forensic entomology

Blowflies use discrete, ephemeral breeding sites for larval nutrition. After exhaustion of the food supply, the larvae disperse in search of sites to pupate or to seek other sources of food in a process known as post-feeding larval dispersal. In this study, some of the most important aspects of this process were investigated in larvae of the blowflies Chrysomya megacephala exposed to a variety of light: dark (LD) cycles (0:0 h, 12:12 h and 24:0 h) and incubated in tubes covered with vermiculite. For each pupa, the body weight and depth of burrowing were determined. Statistical tests were used to examine the relationship of depth of burrowing and body weight to photoperiod at which burrowing occurred. The study of burial behavior in post-feeding larval dispersing can be useful for estimating the postmortem interval (PMI) of human corpses in forensic medicine.

Constant coefficient tests for random coefficient regression

Random coefficient regression models have been applied in differentfields and they constitute a unifying setup for many statisticalproblems. The nonparametric study of this model started with Beranand Hall (1992) and it has become a fruitful framework. In thispaper we propose and study statistics for testing a basic hypothesisconcerning this model: the constancy of coefficients. The asymptoticbehavior of the statistics is investigated and bootstrapapproximations are used in order to determine the critical values ofthe test statistics. A simulation study illustrates the performanceof the proposals.

Nymph developmental time and survivorship, adult longevity, reproduction and body weight of Dichelops melacanthus (Dallas) feeding on natural and artificial diets

The biology of nymphs and adults of the neotropical pentatomid, Dichelops melacanthus (Dallas), feeding on the natural foods, soybean, Glycine max (L.) Merrill immature pods, and corn, Zea mays L. immature seeds, and on an artificial dry diet, was studied in the laboratory. Nymph developmental time was shorter on the natural foods (ca. 21-22 days) than on the artificial diet (28 days), and most nymphs reached adulthood on the food plants (55% on soybean and 73% on corn) than on the artificial diet (40%). Fresh body weight at adult emergence was similar and higher for females raised as nymphs on the natural foods, compared to females from nymphs raised on the artificial diet; for males, weights were similar on all foods. Mean (female and male) survivorship up to day 20, decreased from 55% on soybean to 40% on corn, down to 0% on the artificial diet. Total longevity for females was higher on soybean, while for males was similar on all foods. About three times more females oviposited on soybean than on corn, but fecundity/female was similar on both foods. On the artificial diet, only one out of 30 females oviposited. Fresh body weight of adults increased significantly during the first week of adult life, and at the end of the 3rd week, weight gain was similar on all foods.

Take-the-best and other simple strategies: Why and when they work 'well' in binary choice

The effectiveness of decision rules depends on characteristics of bothrules and environments. A theoretical analysis of environments specifiesthe relative predictive accuracies of the lexicographic rule 'take-the-best'(TTB) and other simple strategies for binary choice. We identify threefactors: how the environment weights variables; characteristics of choicesets; and error. For cases involving from three to five binary cues, TTBis effective across many environments. However, hybrids of equal weights(EW) and TTB models are more effective as environments become morecompensatory. In the presence of error, TTB and similar models do not predictmuch better than a naïve model that exploits dominance. We emphasizepsychological implications and the need for more complete theories of theenvironment that include the role of error.