Energy requirements and energy expenditure of elderly men.

Basal metabolic rates (BMR) and energy cost of a few activities were measured in healthy men aged 63 to 77 years who were participants in a study of protein requirements (previously reported). The men were confined to a metabolic unit for 47 days and received a defined formula diet. Their body weights were 8 to 19 kg higher than that of younger men of the same heights and their whole body potassium content was 12% less than that of younger men (average 28 years of age) studied in the same unit. BMR of the older men was 1622 +/- 189 kcal/day, a figure 13% below the per diem rate of younger men but the same per unit of body potassium. Energy cost of sedentary activities was related to BMR. Expenditure while lying at rest was 1.22 X BMR and while sitting quietly, 1.30 X BMR; these values are the same as in younger men. Walking level at about 2.5 mph cost 4.51 +/- 0.34 kcal/min (about 4 X BMR) and cycling at a comfortable load (300 to 400 kpm) only slightly more. Energy intake required to maintain body weight of these men, who were sedentary except for 30 min of cycling daily, was 2554 +/- 222 kcal/day, or about 1.6 X BMR. Minimum maintenance energy requirement (i.e., ambulatory but inactive) of healthy older men appears to be 1.5 X BMR, the same as in other age groups.