Performance of normal-weight and underweight men with marginal changes in energy intake
Chiplonkar, S.A.; Agte, V.V.; Sukhatme, P.V.
Nutrition 8(5): 326-332
1992
ISSN/ISBN: 0899-9007 PMID: 1421779 Document Number: 394947
The continuous responses of 6 underweight (UW) (body mass index (BMI) <18 kg/msuperscript 2) and 6 normal-weight (NW) (BMI 20-25 kg/msuperscript 2) men of similar age to a modest but sustained level of underfeeding and overfeeding were compared. Habitual energy intake over 4 weeks, body composition and basal metabolic rate (BMR) were estimated under metabolic-ward conditions. NW subjects were heavier by 9 kg and had 5% more body fat than UW subjects. The average BMR of UW subjects was 7.5% lower than NW subjects in absolute terms and also per kg fat-free mass per day but was higher by 8% when expressed per kg body weight per day. 3 NW and 3 UW subjects were given a diet with 10% less energy than their habitual intake for 4 weeks. Finally, they were overfed by 10% for 4 weeks. This sequence was reversed in the remaining 6 subjects. UW subjects showed a quick and vigorous reduction in BMR (13.4%) during the 1st week of underfeeding compared with NW subjects (8.1%). In the later weeks, the reduction was 8% in UW and 7% in NW subjects. Furthermore, UW subjects showed a tendency to resist a decrease in body weight (mean loss 180 g), unlike NW subjects (mean loss 730 g). With overfeeding, the mean increase in BMR for UW was higher (7.4%) than for NW (5.3%) subjects. UW subjects also increased their body weight to a greater extent (mean gain 1.1 kg) than NW subjects (mean gain 0.4 kg). The results indicate that both groups were able to adjust to modest changes in intake, but body-weight control mechanisms operated in a different manner in UW than in NW subjects.