EFFECTS OF EXERCISE ON APPETITE CONTROL - LOOSE COUPLING BETWEEN ENERGY-EXPENDITURE AND ENERGY-INTAKE

The relationship between physical activity and energy intake (food con sumption) can take a number of forms, depending on the intensity, dura tion and frequency of the activity, and upon the degrees of fitness an d physiological status of the individual. At extremes of energy expend iture such as those found in long distance cyclists, voluntary energy intake may be sufficient to balance the enormous daily expenditure; th is is due to an entraining effect. Under more normal situations, there is a widely held belief that physical activity is a poor strategy for losing weight, since the energy expended drives up hunger and food in take to compensate for the energy deficit incurred. Recent studies in both normal weight and obese individuals show that substantial periods of exercise do not increase hunger and do not drive up food intake. C omparisons between sedentary and normally active individuals, or betwe en enforced periods of rest or strenuous activity, generate little or no effect on levels of hunger or daily energy intake, indicating a rat her loose physiological coupling between energy expenditure and food i ntake. This view generates an optimistic view of the role of exercise in weight loss and weight control, as it indicates that intake is not automatically driven up to compensate for energy expended. Reasons why physical activity often produces disappointing effects, rise from ina ppropriate food choices, a desire for self-reward after exercise and m isjudgements about the relative rates at which energy can be expended (by exercise) or taken in (by eating). This means that physical activi ty will be most beneficial for weight control, if carried out in conju nction with a low energy dense diet or with judicious control of eatin g.