8. FOOD, GROWTH AND TIME

by Professor R. A. McCance

Growth is a complicated and highly integrated process, and it has been known for centuries that all parts of the body do not develop equally fast or at the same time. Bones - some in particular - have relatively high "priorities", and it was known to Xenophon (400 B.C.), for instance, and reported by Markham (1617), that one could predict the ultimate size of a horse from the measurement of its shin bone at birth.

Undernutrition reduces the rate of growth. This must have been known for thousands of years: the literature on the subject is enormous. Undernutrition, however, does more than this. By limiting the supply of nutrients and growth materials it accentuates the development of those parts which have at the time in question greater structural stability and perhaps mitotic activity than the rest. Thus, it alters the whole form and shape of the animal as well as its rate of growth. Since bones have relatively high priorities, growth in height is interfered with less than growth in weight, which results from muscular development and the accumulation of fat, and consequently the animal is tall and thin.

In the race against time which characterises the whole period of growth, from conception to maturity, undernutrition is always a disadvantage. The prolongation of life, on the other hand, may be thought of as a feat of endurance rather than a race against time, and in it undernutrition curiously enough may be advantageous. McCay et al. (1939) showed that if rats were subjected to prolonged and severe undernutrition from the time of weaning, many of them fell by the wayside from the hazards involved, but the remainder lived up to three times as long as the normal rat.

However beneficial a high plane of nutrition may be during growth, if it leads to obesity in an adult man it shortens the length of time he is likely to live to enjoy it. Life-assurance statistics demonstrate this, and experiments prove it for animals. In some species the cause is known and genetically obese animals can be protected against themselves by controlling their food intake.

(from The Lancet, 29th September, 1962)