The Response to Long-Term Overfeeding in Identical Twins

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Abstract

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.

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Role of deep abdominal fat in the association between regional adipose tissue distribution and glucose tolerance in obese women.

S Pinault, M Ferland, Andre G Theriault … (1989)

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)

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Deliberate overfeeding in women and men: energy cost and composition of the weight gain.

S Welle, B Lipinski, I W G Forbes … (1986)

1. Thirteen adult females and two males were overfed a total of 79-159 MJ (19,000-38,000 kcal) during a 3-week period at the Clinical Research Center, Rochester. The average energy cost of the weight gain was 28 kJ (6.7 kcal)/g, and about half the gain consisted of lean body mass (LBM) as estimated by 40K counting. 2. A survey of the literature disclosed twenty-eight normal males and five females who had been overfed a total of 104-362 MJ (25,000-87,000 kcal) under controlled conditions: twenty-five of these had assays of body composition, and three had complete nitrogen balances. 3. When these values were combined with those from our subjects (total forty-eight), there was a significant correlation between weight gain and total excess energy consumed (r 0.77, P less than 0.01) and between LBM gain and excess energy (r 0.49, P less than 0.01). Based on means the energy cost was 33.7 kJ (8.05 kcal)/g gain and 43.6% of the gain was LBM; from regression analysis these values were 33.7 kJ (8.05 kcal)/g gain and 38.4% of gain as LBM. 4. Individual variations in the response could not be explained on the basis of sex, initial body-weight or fat content, duration of overfeeding, type of food eaten, amount of daily food consumption or, in a subset of subjects, on smoking behaviour. 5. The average energy cost of the weight gain was close to the theoretical value of 33.8 kJ (8.08 kcal)/g derived from the composition of the tissue gained.

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The effect of 6 weeks of overfeeding on the body weight, body composition, and energy metabolism of young men.

N G Norgan, J V Durnin (1980)

The effect of overfeeding on the body weight, body fat, water content, energy expenditure, and digestibility of energy and nitrogen was investigated over 42 days in six young men. The metabolic rates in standard situations of work and rest were determined. Energy intakes were apparently increased by 6.2 MJ/day and energy expenditure fell slightly by 0.3 MG/day during overfeeding. Fecal and urinary losses of energy were a similar proportion of the gross energy intake in control and overfeeding periods (8%). Metabolizable energy intakes calculated from food tables agreed well with values derived from digestibility measurements in the control period (mean difference = +2%) but not in the overfeeding period (+8%). The implications of this are discussed. Mean body weight gain was 6.0 kg, 10% of initial weight; mean fat gain was 3.7 kg and water gain 1.8 liter. There were considerable interindividual differences in the weight and fat gain for a given excess energy intake. Metabolic rates in standard tasks were 10% higher at the end of overfeeding but expressed as kilojoules per kilogram per minute were similar to control values. Mean energy gain (144 MJ = fat gain X 39 kJ/g) was less than excess energy intake even allowing for overestimation of intakes using food tables and increases in metabolic rate. Such a discrepancy is unlikely to be due to unmeasured increases in metabolic rate but could have arisen from errors in the calculation of the variables involved. In this study where moderate weight gains were achieved by overfeeding mainly fat, increases in metabolic rate appear to be associated with increased body size and tissue gain rather than a luxuskonsumption mechanism.