Body composition and energy metabolism in elderly people

<p>This thesis describes several studies related to the three components of energy balance in elderly people: body composition, energy expenditure, and energy intake.<p><em>Body composition.</em> The applicability of the body mass index, skinfold thickness method, and multi-frequency bioelectrical impedance was tested in elderly men and women. The first two methods predicted body fat in elderly people on a group level with a mean prediction error of 5%. The impedance method predicted total body water (at 50 kHz) and extra-cellular water (at 5 kHz) with a mean prediction error of 8-9%. Individual predictions should be interpreted carefully. Data from 2341 elderly men and women showed that smoking and physical inactivity were associated with a more abdominal fat distribution in men but not in women.<p><em>Energy expenditure. To</em> investigate the possible changes in energy expenditure with aging, energy expenditure at rest (RMR), after a meal of 1.3 MJ (DIT), and during physical activities was measured in elderly men and women and compared with values of young subjects. (RMR), was lower in elderly subjects, which could not be explained by differences in body composition or fat distribution. No relation between DIT and age 'per se' was observed. The energy costs of several physical activities, performed at a self- selected pace, were similar as compared to reference values based on young subjects.<p><em>Energy intake.</em> The reported energy and protein intake of elderly women, obtained by the dietary history method, was validated using measurements of total energy expenditure and urinary nitrogen excretion. An underestimation of 10-12% of the dietary intake was observed.<p>These studies suggest that the decreasing energy requirement with aging is explained by a decrease in (RMR), DIT and possibly a lower physical activity level. The decrease is partly explained by changes in body composition.