REVIEWEffects of physical activity on food intake
Introduction
Physical activity (PA) is closely interrelated with energy intake. The working body requires energy and nutrients in order to fuel activity and function. PA, on the other hand, manipulates energy expenditure and regulates the use of fuels. When prolonged strenuous PA is performed on a regular basis, it causes an increase in overall energy turnover1 and leads either to loss of body weight, or to a need for an increase in food intake.2 Nevertheless, many questions remain open in that regard. For example: is increased energy expenditure due to short-term PA automatically compensated for by changes in energy intake? Does short-term exercise have the same effect on energy intake as long-term exercise? Does the eventual increase in food intake due to increased PA follow the same pattern in obese as in lean individuals?
Thus, to which extent the energy intake is regulated through PA still remains unclear and further research is required that may provide useful information for public health guidelines. For example, vigorous PA on a daily basis not only increases the overall intake of energy,3 but also of other constituents of food, such as micronutrients. Therefore, in conjunction with low-energy food abundant in minerals and vitamins, PA may not only enhance human health in general,4 but also prevent micronutrient deficiencies.5
Therefore, reaching a clear understanding of the relationship between PA and food intake may prove valuable in choosing the most beneficial approach for individual and societal health management. The aim of this paper is thus to summarize the state-of-art in our understanding of the effects of PA on energy and nutrient intake.
Section snippets
Relationship between food intake, body mass and physical activity
Mayer et al.6, 7 performed several of the earlier studies, on both animals and humans, examining the effect of exercise on body mass and food intake. To the extent that it is legitimate to draw an equivalence between purely experimental results and the results of population studies, a remarkable parallelism was found between the two.7 In order to provide an accessible overview of these and other findings on the same topic, the relationship between food intake, exercise and body mass is
Effects of sedentarism on food intake
In mice, under laboratory conditions, the decrease in energy expenditure due to reduced activity is not accompanied by a corresponding decrease in energy intake.8 Thus, physical inertia in mice is considered to play an essential role in the development of obesity.
The influence of inactivity on energy balance was investigated in humans by Murgatroyd et al.9 Two-day measurements of energy expenditure in the respiration chamber, and ad libitum food intake were measured in eight normal-weight male
Energy intake in response to high-energy requirements
Animals and humans who engage regularly in moderate to intense PA are capable of maintaining their lean body mass.6, 7 An important aspect of the maintenance of energy balance during high-intensity endurance exercise is an adjustment of food intake to high-energy requirements. An example of daily energy intake in endurance, strength, and team sport athletes are presented in Table 1.14 The nutritional information about habitual food intake was obtained from a 4 or 7-day food diary on athletes,
Effect of short-term exercise on food intake
In highly physically trained persons, the enormous daily energy expenditure due to vigorous exercise is thus generally matched by a high-energy intake (Fig. 1, zone 3).15 By contrast, under more normal conditions, increased energy expenditure due to short-term PA is not automatically compensated for by changes in energy intake in both, lean and obese individuals (Fig. 1, zone 2).19
King et al.20 examined the effect of different types of short-term exercise on energy intake. Twenty-three healthy
Regulation of energy intake
The absence of a compensatory effect in response to an exercise-induced energy deficit would not be expected to continue indefinitely; otherwise a considerable loss of body mass would occur. At some stage, a regulatory mechanism must trigger an increase in energy intake in order to match energy expenditure. This mechanism reflects an active regulatory process within a human body, termed energy homeostasis.29 Its variation is associated with changes in body weight and more specifically, with
Effects of long-term exercise on food intake in lean and obese subjects
It is clear that, as energy output is increased through exercise, in order to maintain body mass, an individual must increase energy intake to match expenditure. The lean marathon-runner eats much more calories than his sedentary counterpart.45 Many reports in the literature confirm the existence of this balancing act over the long term. Even though the present obesity epidemic needs more insight into the effects of increasing energy expenditure in obese and lean individuals, several studies
Conclusion
Increased energy expenditure due to short-term PA is not immediately compensated for by changes in energy intake. Once moderate to intense PA is performed regularly and on the long-term basis, however, a distinction has to be drawn between lean and obese subjects. While the lean show a tendency to balance the extra PA energy expenditure by adapting their energy intake accordingly within a period, of about 3 days, the obese, probably due to their excess energy storage, do not show such a
Acknowledgement
We thank the Foundation Nutrition 2000Plus for its financial support.
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