3.2. Longer-term study in a clinical setting

Five boys, 25 to 40 months old, participated in a longer-term study, also under strict supervision at INCAP's Clinical Center (TORUN and VITERI, 1981a). Dietary modifications only involved decreases in energy density, without changes in protein, vitamin and mineral contents, and the energy reductions were of a smaller magnitude than in the preceding study.

The children first ate a diet that provided net or metabolizable energy (i.e., food energy minus fecal energy, measured by bomb calorimetry) equivalent to 90 ±3 kcal/kg/d, which had been shown to be the requirement of similar children living at INCAP's Clinical Center (VITERI et al., 1981; TORUN and VITERI, 1981b). The energy content of the diet was then reduced twice at 40-day intervals. During these experimental periods the children ate the equivalent of 82 ±4 and 71 ±4 metabolizable kcal/kg/d. The lower of those levels of intake is often found in dietary surveys among low-income preschool children in Guatemala.

The children were encouraged, but not forced, to participate in active play several times each day. Their energy expenditure was calculated every 20 days from individual calibrations of heart rate to oxygen consumption relationship and heart rate monitoring during the day, and from their basal metabolic rates at night.

Table 2 shows that the reduction in energy intake from 90 to 82 kcal/kg/d was accompanied by a decrease in total daily energy expenditure (p < 0.025) without affecting weight gain. An additional reduction of intake to 71 kcal/kg/d did not significantly affect expenditure, but weight gain was markedly reduced (p < 0.01). Growth in height was not affected.

Table 2. Total energy expenditure, energy balance and weight gain of 5 children with successive reduction in energy intake (mean ±standard deviation) ^a

a Energy expenditure calculated from heart rate and the corresponding heart rate to energy expenditure relationship during the day, and from BMR at night. Energy balance calculated from gross energy intake (bomb calorimetry) - fecal energy (bomb calorimetry) - estimated urine and sweat energy - energy expenditure.

^b Net dietary energy = dietary - fecal energy, measured by bomb calorimetry.

Differs from the two other levels of intake: * p < 0.025; ** p < 0.01.

Source: TORUN and VITERI, 1981a.

Energy balance was calculated from gross dietary energy (bomb calorimetry), minus fecal energy (bomb calorimetry), minus urinary energy (estimated at 5 kcal/g urinary nitrogen), minus sweet losses (estimated at 0.1 kcal/kg/d, based on 8 kcal/g sweat nitrogen), minus total energy expenditure. Table 2 shows that, on the average, the children were near equilibrium and there were no differences in the mean energy balances with the different levels of dietary energy intake. Since BMR did not change throughout the study, energy balance was maintained through a reduction of energy expenditure in activity after the first dietary modification, and mostly through weight loss or a decrease in weight gain after the second dietary energy reduction.