The enigma of mass regulation

Abstract

The factors involved in the regulation of body mass, particularly those relating to the special case of obesity, are considered in the light of recent investigations which often make use of techniques not previously available. Attention is first drawn to certain difficult:es arb;ng in the diagnosis and in the estimates of the prevalence of obesity. After a brief consideration of the components of body mass and the metabolism of fat, whether normal or abnormal, the numerous factors influencing the intake and expenditure of energy are examined in some detail, together with the way in which the body responds when the balance of energy is deliberately altered by dietary changes. This leads to an examination of the mechanisms known to exert a regulatory effect on our mass, especially the new role assigned to adipose tissue. A good deal of the work described is new and may need revision, but evidently some cherished ideas must be modified if not abandoned, such as the widespread assumption that mass varies more or less automatically according to the amount of food eaten or the amount of exercise taken, or both. It is suggested that whether a person tends to gain, or maintains an almost constant mass over long periods, or is intractably thin, depends on the behaviour of mass-regulating mechanisms that are more numerous, complex, interrelated and powerful than was formerly suspected. Which of these patterns develops is primarily determined by heredity, but can be modified by the environment, particularly during the early stages of development. In other words, mass pattern is an expression of the constitution.

S. Afr. Med. J., 48, 287 (1974).