3.1. Short-term study in a clinical setting

A direct effect of food intake on activity was clearly demonstrated in short-term studies of well-nourished Guatemalan children who had fully recovered from protein-energy malnutrition, before and after taking them off the high-energy, high-protein therapeutic diet (VITERI and TORUN, 1981). A minute-by-minute time-motion technique was used under controlled clinical conditions to record the activities of 5 boys, 1.5-4.5 years old, on 4 days prior to, and in the last 4 days of a week during which dietary intake was reduced from 120-150 kcal and 3-4 g protein/kg/d to the 70-90 kcal and 1.8-2.0 g protein/kg/d provided by the home diets of most children from poor Guatemalan families. Supplementation with vitamins and minerals did not change.

Table 1 and Figure 3 show that the time spent in the more energy-demanding activities was reduced, on the average, by 17 to 56%. In contrast, the time spent lying down in the games' room, either resting or in sedentary play, increased twofold.

Table 1. Changes in time allocated to different physical activities by 6 preschool children after dietary intake was reduced from 120-150 to 70-90 kcal/kg/d (mean of 4 days)

Change relative to initial time allocation	Sleeping or resting in bed	Lying down in games' room	Eating or sitting	Standing activities	Walking or running	Riding tricycle *	Other games and activities
Minutes/day	+68	+48	+4	-81	-17	-15	-4
% change	+8	+112	+1	-56	-23	-52	-17

* n = 4
Source: VITERI and TORUN, 1981.

Figure 3a. Reduction in time spent by preschool children in energy-demanding activities after decreasing dietary energy from 120-150 (Control) to 70-90 (Experimental) kcal/kg/d. From VITERI and TORUN, 1981. A. Standing.

Figure 3b. Reduction in time spent by preschool children in energy-demanding activities after decreasing dietary energy from 120-150 (Control) to 70-90 (Experimental) kcal/kg/d. From VITERI and TORUN, 1981. B. Walking - running.

Figure 3c. Reduction in time spent by preschool children in energy-demanding activities after decreasing dietary energy from 120-150 (Control) to 70-90 (Experimental) kcal/kg/d. From VITERI and TORUN, 1981. C. Riding tricycle.

Figure 3d. Reduction in time spent by preschool children in energy-demanding activities after decreasing dietary energy from 120-150 (Control) to 70-90 (Experimental) kcal/kg/d. From VITERI and TORUN, 1981. D. Other active games.

Basal metabolic rate remained constant at 55 ±5 and 53 ±4 kcal/kg/d (mean ±SD), before and one week after the dietary change, respectively. Using indirect calorimetric measurements for some activities and estimates of the energy cost of others, it was calculated that, on the average, the children were in energy balance during the two weeks with standard deviations of 19 and 27 kcal/kg/d, respectively. Mean weekly weight changes decreased from 2.5 ±1.2 to -0.5 ±0.6 g/kg/d. The mean weight gain expected in healthy children of the same ages and heights, eating home diets with about 100 kcal/kg/d, is approximately 0.6 g/kg/d (US-NCHS, 1976; FAO/WHO/UNU, 1985).

This study showed that changes in activity pattern occur within a few days of the reduction in dietary energy intake. It is unlikely that this was due to the concurrent decrease in protein intake, as even the lower diet contained more than the recommended safe levels of protein (FAO/WHO/UNU, 1985).