| Abstract: | Six healthy male volunteers were confined to a metabolic unit for 105 days. Energy intake (EI) and energy expenditure (EE) were varied in order to achieve either a marginally negative (-15%) or an equilibrated energy balance (EB), in different metabolic periods (MP) as follows: MP I: EE = 1, EI = 1, EB = 0; MP II: EE = 1, EI = 0.85, EB = -15%; MP III: EE = 0.85, EI = 0.85, EB = 0; MP IV: EE = 0.85, EI = 0.70, EB = -15%; MP VI: EE = 1.15, EI = 1.15, EB = 0; MP VII: EE = 1.15, EI = 1, EB = -15%. An egg protein formula diet was fed throughout the study. The amount given in MP I was sufficient to maintain body weight constant. Assigned physical activity consisted of regulated walking and cycling. During MP I, this physical activity accounted for 15% of the energy intake. Serum insulin, insulin binding to erythrocytes and body fat content were determined at the end of each MP. No significant changes were found in serum insulin level throughout the study, but specific insulin binding did change significantly. Binding increased with increased physical activity by 23% at the end of MP VI and an additional 35% at the end of MP VII. The maximum percentage of insulin binding to erythrocytes correlated inversely with the percentage of body fat in each MP. These data suggest that insulin binding to erythrocytes, in normal men, is sensitive to a small change in energy balance, and especially to physical activity.(ABSTRACT TRUNCATED AT 250 WORDS) |
