We undertook this study to determine whether there are differences in the responses of different persons to long-term overfeeding and to assess the possibility that genotypes are involved in such differences. After a two-week base-line period, 12 pairs of young adult male monozygotic twins were overfed by 4.2 MJ (1000 kcal) per day, 6 days a week, for a total of 84 days during a 100-day period. The total excess amount each man consumed was 353 MJ (84,000 kcal). During overfeeding, individual changes in body composition and topography of fat deposition varied considerably. The mean weight gain was 8.1 kg, but the range was 4.3 to 13.3 kg. The similarity within each pair in the response to overfeeding was significant (P less than 0.05) with respect to body weight, percentage of fat, fat mass, and estimated subcutaneous fat, with about three times more variance among pairs than within pairs (r approximately 0.5). After adjustment for the gains in fat mass, the within-pair similarity was particularly evident with respect to the changes in regional fat distribution and amount of abdominal visceral fat (P less than 0.01), with about six times as much variance among pairs as within pairs (r approximately 0.7). We conclude that the most likely explanation for the intrapair similarity in the adaptation to long-term overfeeding and for the variations in weight gain and fat distribution among the pairs of twins is that genetic factors are involved. These may govern the tendency to store energy as either fat or lean tissue and the various determinants of the resting expenditure of energy.

A variety of studies has a need to estimate the amount and pattern of daily energy expenditure. To this end, a 3-day activity record was developed and is described. Every 15-min period over 3 days, including a weekend day, was qualified in terms of energy cost on a 1 to 9 scale corresponding to a range of 1.0 MET to 7.8 METs and higher. A reliability study of 61 subjects indicated a highly reproducible procedure as shown by an intraclass correlation of 0.96 for mean kcal of energy expenditure over 3 days. Repeatability was unchanged whether or not the hours of sleep were included in the record. Samples of 150 children and 150 adults were also drawn to investigate the relationship between energy expenditure, physical working capacity, and body fatness. Results support the hypothesis that mean energy expenditure per kg of body weight is significantly correlated with physical working capacity expressed per kg of body weight (r = 0.31; p less than 0.01). Mean energy expenditure per kg of body weight is negatively related to body fat (-0.08 less than or equal to r less than or equal to -0.13). It is concluded that the 3-day activity record is a procedure suitable to estimate energy expenditure in population studies.

Computed tomography (CT) was used to study the association between adipose tissue localization and glucose tolerance in a sample of 52 premenopausal obese women aged 35.7 +/- 5.5 yr (mean +/- SD) and with a body fat of 45.9 +/- 5.5%. Body-fat mass and the body mass index (BMI) were significantly correlated with plasma glucose, insulin, and connecting peptide (C-peptide) areas after glucose (75 g) ingestion (.40 less than or equal to r less than or equal to .51, P less than .01). Trunk-fat accumulation and the size of fat cells in the abdomen displayed highly significant correlations with postglucose insulin levels. The C-peptide area was also positively correlated with abdominal fat cell size (r = .76, P less than .01) and was more closely associated with the sum of trunk skin folds (r = .59, P less than .001) than with the extremity skin folds (r = .29, P less than .05). Subcutaneous and deep-abdominal-fat areas measured by CT displayed comparable associations with the plasma insulin area (r = .44 and .49, respectively; P less than .001) but marked differences in the associations with glucose tolerance. Indeed, subcutaneous abdominal fat was not significantly correlated with the glucose area, whereas deep abdominal fat showed a significant correlation (r = .57, P less than .001) with the glucose area. Midthigh fat deposition measured by CT was not, however, correlated with plasma glucose, insulin, or C-peptide areas.(ABSTRACT TRUNCATED AT 250 WORDS)

1.Abdominal obesity is associated with numerous metabolic complications. Deep abdominal adipose tissue is critical in the association between the level of abdominal obesity and cardiovascular risk factors.2. Adipose tissue localization was assessed by computed axial tomography (CAT), and its association with body density and anthropometric measurements was investigated in a sample of fifty-one obese women (percentage body fat 45.9 (SD 5.6)) aged 35.7 (SD 5.5) years. The CAT scans were performed at three levels: lower chest, abdomen and mid-thigh.3. The total adipose tissue volume computed from these three scans was highly correlated with body fat mass (r 0.94, P < 0.001). The proportion of deep abdominal fat as measured by the ratio of deep: total adipose tissue areas at the abdominal level was not significantly correlated with body fat mass, but it was moderately associated with the ratio of waist: hip circumferences (WHR) (r 0.49, P i 0.001). The absolute amount of deep abdominal fat was, however, significantly correlated with body fat mass (r 0.72, P < 0.001).4. The subscapular (r 0.38) and the abdominal (r 0.38) skinfolds were the only two skinfolds that were significantly associated with the proportion of deep abdominal fat (P < 0.01). These skinfolds were also those which showed the highest correlation with the absofute amount of deep abdominal fat (r 065, P < 0-001, for both skinfolds). 5.A three-site CAT-scan procedure can be used for the estimation of body fat mass in premenopausal obese women.6. In these obese women, there was no significant association between total adiposity and the proportion of deep adipose tissue at the abdominal level.7. In premenopausal obese women, the absolute amount of deep abdominal fat can be predicted from anthropometric measurements with more accuracy than the relative amount of deep abdominal fat.

Seven pairs of young adult male identical twins completed a negative energy balance protocol during which they exercised on cycle ergometers twice a day, 9 out of 10 days, over a period of 93 days while being kept on a constant daily energy and nutrient intake. The total energy deficit caused by exercise above tlie estimated energy cost of body weight maintenance readied 244 f 9.8 MJ (Mean f SEM).Baseline energy intake was estimated over a period of 17 days preceding the negative energy balance protocol. M e a n body weight loss was 5.0 kg (SEM = 0.6) (p < 0.001) and it was entirely accounted for by tlie loss of fat mass (p < 0.001). Fat-free mass was unchanged. Body energy losses reached 191 MJ (SEM = 24) (p < 0.001) wliicli represented about 78% of the estimated energy deficit. Subcutaneous fat loss was sliglitly more pronounced on the trunk than on the limbs as estimated from skinfolds, circumferences, and computed tomograpliy (CT). The reduction in CT-assessed abdominal visceral fat was quite striking, from 81 cm2 (SEM = 5) to 52 cm2 (SEM = 6) (p < 0.001). A t tlie same submaximal power output level, subjects oxidized more lipids than carbohydrates after tlie program as indicated by tlie changes in the respiratory exchange ratio (p 10.05). Intrapair resemblance was observed for tlie changes in body weight (p < 0.05), fat mass (P < 0.01), percent fat (p < 0.01), body energy content (p < 0.01), sum of 10 skinfolds (p < 0.01), abdominal visceral fat (p < 0.01), fasting plasma triglycerides (p < 0.05) and cliolesterol (p < 0.05), maximal oxygen uptake (p < 0.05), and respiratory exchange ratio during submaximal work (p < 0.01). We conclude that even though there were large individual differ- ences in response to the negative energy balance and exercise protocol, subjects with tlie same genotype were more alike in responses than sulljects with different genotypes particularly for, body fat, body energy, and abdominal visceral fat changes. High lipid oxidizers and low lipid oxidizers during submaximal exercise were also seen despite the fact that all subjects liad experienced tlie same exercise and nutritional conditions for about three montlis.