Behavioral Compensatory Adjustments to Exercise Training in Overweight Women

Eirini Manthou; Jason M. R. Gill; Andrea Wright; Dalia Malkova

Disclosures

Med Sci Sports Exerc. 2010;42(6):1121-1128. 

In This Article

Abstract and Introduction

Abstract

Purpose: The purpose of this study was to examine the extent to which changes in nonexercise physical activity contribute to individual differences in body fat loss induced by exercise programs.
Methods: Thirty-four overweight or obese sedentary women (age (mean ± SD) = 31.7 ± 8.1 yr, BMI = 29.3 ± 4.3 kg·m−2) exercised for 8 wk. Body composition, total energy expenditure, exercise energy expenditure (ExEE), activity energy expenditure calculated as energy expenditure of all active activities minus ExEE, sedentary energy expenditure, sleeping energy expenditure, and energy intake were determined before and during the last week of the exercise intervention.
Results: Over the 8-wk exercise program, net ExEE was 30.2 ± 12.6 MJ, and on the basis of this, body fat loss was predicted to be 0.8 ± 0.2 kg. For the group as a whole, change in body fat (−0.0 ± 0.2 kg) was not significant, but individual body fat changes ranged from −3.2 to +2.6 kg. Eleven participants achieved equal or more than the predicted body fat loss and were classified as "responders," and 23 subjects achieved less than the predicted fat loss and were classified as "nonresponders." In the group as a whole, daily total energy expenditure was increased by 0.62 ± 0.30 MJ (P < 0.05), and the change tended to be different between groups (responders = +1.44 ± 0.49 MJ, nonresponders = +0.29 ± 0.36 MJ, P = 0.08). Changes in daily activity energy expenditure of responders and nonresponders differed significantly between groups (responders = +0.79 ± 0.50 MJ, nonresponders = −0.62 ± 0.39 MJ, P < 0.05). There were no differences between responders and nonresponders for changes in sedentary energy expenditure and sleeping energy expenditure or energy intake.
Conclusion: Overweight and obese women who achieved lower than predicted fat loss during an exercise intervention were compensating by being less active outside exercise sessions.

Introduction

Increasing total energy expenditure (TEE) by increasing physical activity is an important component of many lifestyle interventions aimed at reducing obesity and its complications. Such increases in TEE should aid body fat and body weight loss, provided all other variables affecting energy balance are kept constant. However, exercise-induced perturbations to energy balance may initiate behavioral compensatory adjustments and either alter food intake[24,27,33,34,36] or cause a reduction in normal daily activities.[11,16,21,36] This compensation for the exercise-induced energy deficit may explain why exercise alone often does not result in successful weight loss in obese and overweight individuals.[12]

Despite the commonly reported and accepted notion that the effectiveness of exercise in inducing body fat loss is low, an accumulating body of evidence suggests that the interindividual variability in body weight and fat changes in response to an exercise intervention is large and that participants of exercise intervention studies can broadly be separated into "responders," that is, those who achieve a body fat loss in response to exercise, and "nonresponders," that is, those who fail to achieve a body fat reduction in response to exercise.[3,22,23] This suggests that studies investigating exercise-induced compensatory mechanisms should focus on individual variability rather than consider body fat or body weight changes in the group as a whole. In addition, such studies should ensure adherence to prescription of exercise because variability in the effectiveness of exercise in relation to body fat loss could be accounted for difference in compliance.[8,10]

Data evaluating individual responsiveness to exercise-induced fat loss are very limited. The recent study of King et al.[23] investigated compensatory responses to a supervised and well-controlled exercise program in overweight men and women in relation to individual variability. The authors reported that participants who experienced a lower than predicted weight loss demonstrated a compensatory increase in their energy intake over the course of the intervention and that those who lost more weight than predicted decreased energy intake, although there was no overall difference before and after the intervention for the group as a whole. Although compensating for exercise-induced energy disturbance could also include alterations in physical activity in nonexercise time,[11,16,21,34] this was not investigated in the aforementioned study.

The aim of the present study was therefore to examine the extent to which changes in physical activity outside of the exercise intervention and energy intake contribute to individual differences in body fat loss induced by exercise training programs. The volume of exercise used was based on current exercise recommendations,[18] and compliance to the prescribed exercise was ensured by supervision of all exercise sessions.

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