9 - Assessment of body composition in the obese

Summary

Introduction

Definition of obesity

Obesity is an excess of body fat or perhaps more correctly excessive fatness, since it is the proportion of fat to other tissues in the body, rather than the absolute amount of fat, which is indicative of obesity (Bray, 1992). There is no consensus on either the expected amount of fat, or the degree of fatness which can be considered normal. Moreover it is not clear whether it is the total amount of fat in the body, the proportion of fat or the rate at which excess fat is deposited which is most significant for health and fitness. Definition of obesity is complicated by variations in the normal amount and distribution of fat with age, sex, genetic inheritance and physical fitness, irrespective of nutritional state.

Obesity is considered an abnormal situation and one which in current Western culture carries a social disadvantage although fatness is actually considered desirable in some cultures. Severe obesity carries risks for long term health (Hubert et al., 1983; van Itallie & Abraham, 1985; Garrow, 1988) but correlations between culturally undesirable fatness and medically undesirable fatness have not been made. Obesity is difficult to treat and it seems a waste of health resources to struggle with obesity which is of no significance for health. Thus it would be helpful, although currently not possible, to distinguish fatness which is a cosmetic problem only, from fatness which is likely to endanger life.

Fat is the most variable component of the body. It forms less than 10% of body weight in some individuals and more than 50% of body weight in others.