Total free living energy expenditure was compared in lean and obese women by the new doubly labelled water method and partitioned into basal metabolism and thermogenesis plus activity by whole body calorimetry. Average energy expenditure was significantly higher in the obese group (10-22 versus 7-99 MJ/day (2445 versus 1911 kcal/day); p<0-001) resulting from an increase in the energy cost of both basal metabolism and physical activity. Self recorded energy intakes were accurate in the lean subjects but underestimated expenditure by 3-5 MJ/day (837 kcal/day) in the obese group. Basal metabolic rate and energy expenditure on thermogenesis plus activity were identical in the two groups when corrected for differences in fat free mass and total body mass.In the obese women in this series there was no evidence that their obesity was caused by a metabolic or behavioural defect resulting in reduced energy expenditure.

In patients with HIV infection, total energy expenditure is reduced during episodes of weight loss. Reduced energy intake, not elevated energy expenditure, is the prime determinant of weight loss in HIV-associated wasting.

Twelve women were studied before pregnancy and at 6-wk intervals from 6 to 36 wk gestation. Total energy expenditure (TEE) by the doubly labeled water method, basal metabolic rate (BMR), energy intake, and body composition were assessed on each occasion. There was substantial interindividual variation in the response to pregnancy. Mean total energy costs were as follows: delta BMR 112 +/- 104 MJ (range -53 to 273), delta TEE 243 +/- 279 MJ (range -61 to 869 MJ), and fat deposition 132 +/- 127 MJ (range -99 to 280 MJ). The mean total cost of pregnancy (cumulative TEE above baseline+energy deposited as fat and as products of conception) was 418 +/- 348 MJ (range 34-1192 MJ). This was much higher than current recommendations for incremental energy intakes. Self-recorded incremental intakes (208 +/- 272 MJ) seriously underestimated the additional costs. The variability in response emphasizes the problems in making prescriptive recommendations for individual women, because there is no way of predicting metabolic or behavioral responses to pregnancy.

The doubly-labelled water (2H180) method was used to measure total energy expenditure (TEE) in ten uon-pregnant, non-lactating (NPNL), six pregnant (P) and fourteen lactating (L) women in a rural Gambian community. Measurements were made on free-living subjects at a period of peak energetic stress when high agricultural work loads coincided with a hungry season to induce moderately severe negative energy balance. TEE averaged 10.42 (SD 2.08) MJ/d, equivalent to 1.95 (SD 0.38) times resting metabolic rate (RMR). The energy cost of physical activity plus thermogenesis, derived as TEE -RMR,

The mechanisms by which well-nourished women meet the additional energy costs of lactation were studied by measuring energy intake (EI), basal metabolic rate (BMR), total energy expenditure by doubly labeled water (TEE), physical activity plus thermogenesis (TEE-BMR), changes in body fat stores, and milk energy transfer. Ten women were studied at 36 wk gestation; 4, 8, and 12 wk lactation (L4, L8, L12); and when nonpregnant and nonlactating (NPNL) after weaning. At L4, L8, and L12 the energy transferred in milk averaged 2245, 2225, and 2217 kJ/d with an additional 445 kj/d (106 kcal/d) estimated as being necessary for synthesis. EI was 1360, 1740, and 1275 kJ/d higher than the NPNL values, representing 56% of the costs of lactation. The remaining 44% was met by a reduction in TEE (-945, -688, and -826 kJ/d vs NPNL) caused largely by a reduction in physical activity because BMR was essentially unchanged (+29, -12, and -218 kJ/d). The energy-balancing strategies adopted by different women varied markedly.