The right weight: body fat, menarche and fertility

Abstract

This review begins with consideration of the energy cost of reproduction and female body composition, the relation between body weight and infant survival, and how adipose tissue may regulate female reproduction. Hypothalamic dysfunction, gonadotrophin secretion and weight loss are examined. The physiological basis of reproductive ability is discussed in terms of weight at menarche, the secular trend toward an earlier age at menarche, components of weight at menarche, and fatness as a determinant of minimal weights for menstrual cycles. Other aspects discussed include: physical exercise, delayed menarche and amenorrhoea; psychological stress and changes in weight; evidence from experimental animals (including food intake, ovulation and "flushing"); male reproduction (including the effects of nutrition and exercise). Nutrition, physical work and natural fertility are discussed under the headings: human reproduction reconsidered; the paradox of rapid population growth in undernourished populations; long-term, regular exercise lowers the risk of sex hormone-sensitive cancers; magnetic resonance imaging of body fat of athletes and controls.