INTERACTION BETWEEN PHYSICAL-ACTIVITY AND NUTRITION EARLY IN LIFE ANDTHEIR IMPACT ON LATER DEVELOPMENT

It has been rare to find studies of the influence of nutrition on grow th that have incorporated careful measurements of physical activity. T his paper reviews interactions between physical activity and nutrition in early life and finds that such interactions have a significant inf luence on growth and later metabolism. Young animals are generally cha racterized by a high level of spontaneous motor activity that contribu tes to a high rate of energy turnover in early life. Such activity var ies greatly between species and individuals and can be increased by re duced (but not extreme) dietary intake especially of protein, with con sequent effects on growth rate (slower), body composition (leaner), ev entual body size (smaller), lifespan (longer), cardiac resistance to t oxic substances (increased) and changes in body lipids. Most studies h ave been conducted with laboratory rats but the much smaller literatur e concerning human beings is also reviewed here. In rats, exercise dur ing pregnancy results in off spring that are smaller and leaner and th ere are later improvements in cardiac microstructure, cardiac resistan ce to toxic substances and lower plasma cholesterol and triacylglycero l concentrations. In industrialized countries in recent years, childre n's fitness, especially of the cardiorespiratory system has not develo ped at the same pace as body size, or has deteriorated, whereas averag e body mass index (BMI) and the overall prevalence of obesity have inc reased. This is partly accounted for by reduced levels of physical act ivity but there is some evidence that higher intakes of dietary protei ns in early life are also implicated. Much recent research has focused on the influence of nutrition in the prenatal and early postnatal per iod on. later health. This review has also underlined the importance o f exercise and its interaction with diet beginning with the pregnant m other and continuing through childhood. Development and wider use of s imple but reliable methods for the evaluation of physical activity and fitness in young children is now an important priority.