Body weight and weight change and their health implications for the elderly.

After the age of 60 y, body weight on average tends to decrease. The contribution of fat mass to this weight loss is relatively small, but fat tends to be redistributed with advancing age toward more abdominal (particularly visceral) fat. Anthropometric data are relatively poor indicators of these aging processes. This may be one of the explanations why the relationship between high body mass index and mortality is less pronounced in older than in younger people. Reduced lipolysis in the visceral fat depot with aging is among potential explanations why increased visceral fat seems to be less harmful in elderly subjects compared to young adults. Even though the relative contribution of increased fat mass to mortality may be less pronounced in elderly people, the impact on disability and functional limitations is found to be important from both a clinical and a public health point of view. At the other end of the scale studies have shown that low body mass index and weight loss in the elderly are both strong predictors of subsequent mortality. This cannot be explained by effects of smoking and early mortality after baseline. There are only few systematic studies comparing the predictive validity of different anthropometric data for mortality. One recent prospective study showed that a high waist circumference (in nonsmoking men) may be a better predictor of all-cause mortality than high body mass index and waist/hip ratio. Low BMI was a better predictor of mortality than low waist circumference. In conclusion changes in body composition and fat distribution with aging are poorly captured by standard anthropometric data. Low lean body mass is probably better reflected by low BMI, whereas increased (abdominal) fatness is better reflected by increased waist circumference.