Research Review By Erin Haske©

Date Posted:

December 2010

Study Title:

Behavioral Compensatory Adjustments to Exercise Training in Overweight Women

Authors:

Manthou E, Gill JMR, Wright A, et al.

Author's Affiliations:

Human Nutrition Section, Division of Developmental Medicine, Medical School, University of Glasgow, Scotland; Integrative and Systems Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, Scotland.

Publication Information:

Medicine & Science in Sports & Exercise 2010; 42(6): 1221-1228.

Background Information:

An increase in daily total energy expenditure is an important factor in successful loss of bodyweight and associated fat loss in overweight and obese individuals. An increase in daily physical activity will positively affect a decrease in bodyweight and fat loss, if other energy expenditure and intake remain unchanged. However, increasing daily activity by participation in an exercise program may result in compensatory changes in food intake or other daily physical activity.

Previous data suggests that both reduction in physical activity during non-exercise time (1) and increase in energy intake due to exercise-induced energy deficit may prevent successful decrease in bodyweight and body fat percentage to a degree (2).

Existing evidence suggests that there is a large variability between individuals in non-exercise physical activity and energy intake reactions to increased exercise activity (3), with the individual response determining the extent of bodyweight and fat loss. Generally, individuals can be classed as “responders”, who lose a predicted amount of weight or more, and “non-responders”, who lose less than a predicted amount of weight.

This study is the first to examine these reactions on an individual basis, and to determine the extent to which they affect the bodyweight and fat loss of the individual.

Pertinent Results:

  • When considered as a group, no significant change was found in body fat levels after the eight-week exercise intervention.
  • However, there was a large inter-individual variation in body fat percent changes, with 11 of the 34 participants classes as responders, and 23 of the 34 classed as non-responders.
  • Changes in non-exercise physical activity and energy intake in reaction to increased exercise activity appear to affect the extent of bodyweight and fat loss in the individual.
  • Non-exercise physical activity was higher in responders than non-responders during the exercise intervention period of eight weeks. However, unlike previous studies examining individual responses, no significant difference was found in energy intake between responders and non-responders. This may be due to a difference in prescribed exercise protocols; it is suggested that increased energy intake in reaction to increased exercise activity may be dependent on exercise volume and related energy expenditure, and that the exercise prescribed in this intervention was not of sufficient volume to induce such a reaction.
  • No differences were found in changes to resting metabolic rate between responders and non-responders, and frequency of exercise activity did not affect the individual response.
  • Regardless of changes to body fat levels, all study participants experienced health benefits as a result of increased exercise activity:waist circumference decreased by 4 percent in both responders and non-responders after the eight week intervention, pointing to a redistribution of body fat even when no body fat was lost.
  • Additionally, maximal oxygen consumption was increased by 35 percent for the group as a whole, showing an improvement in cardiorespiratory fitness.
  • No significant differences between groups were evident for either waist circumference or maximal oxygen consumption.

Clinical Application & Conclusions:

When attempting to decrease bodyweight and body fat levels in overweight and obese individuals, implementing strategies aimed at maintaining normal non-exercise physical activity and energy intake may result in greater success. Particular attention should be paid to maintaining normal activity levels outside of exercise. Energy intake may not impact bodyweight and fat loss to the same degree, though this appears to be dependent on the volume of exercise in the specific intervention. Regardless of any change to body fat levels, health benefits may be experienced through increased exercise activity.

Study Methods:

Study participants included thirty-four overweight or obese women (average age: ~32). Participants were weight stable for two months prior to the intervention and were normally sedentary non-smokers who were not on any form of medication. There were no significant differences in baseline measurements of any variable between participants.

Participants performed an eight week, supervised exercise program consisting of 150 minutes of exercise per week at heart rates corresponding to 72%-77% of their age-predicted maximum heart rate. This volume of exercise was based on current exercise recommendations (4). Participants completed their exercise either as two 75-minute sessions per week or five 30-minute sessions per week.

All physical activities were recorded in a physical activity diary for a seven day period prior to the exercise intervention, and also in week eight. Participants were required to wear heart rate monitors during all waking hours during the week prior to, and during week eight of the intervention. Physical activity diaries were time matched to heart rate data, and the rate of energy expenditure was then calculated by indirect calorimetry.

Participants kept a food diary for a seven day period prior to the exercise intervention and in week eight to determine energy intake. Diary entries included a record of weight and time of consumption of all food and drink.

Baseline measurements were repeated at the end of the eight week intervention period to determine statistical significant. Data was tested for normality and logarithmically transformed if needed. Analyses included:
  • Changes from baseline to postintervention assessment were compared by two-way ANOVA with repeated measures on the factor “time”.
  • Group ? time interaction determined whether participants were classified as responders.
  • A post-hoc Tukey test identified changes within groups.
  • Univariate and multivariate regression analyses were used to determine whether energy expenditure or energy intake were significant predictors of the extent of change in body fat mass.
  • Chi-square analysis was used to determine whether exercise frequency influenced individual response.

Study Strengths / Weaknesses:

Study limitations that should be considered include the following:
  • Potentially inaccurate food and drink intake records, due to data collection errors and/or underreporting. It should be noted that the extent of underreporting appears to be consistent within the individual.
  • Volume and intensity of exercise intervention (moderate) may not have been high enough to elicit reactionary changes in non-exercise physical activity or energy intake behavior.
  • There is no gold standard technique for assessing components of total energy expenditure (i.e. non-exercise physical activity, other activity, or inactivity). The gold standard of total energy expenditure measurement, the doubly labeled water method, does not allow for calculation of separate components.
  • The eight week intervention was relatively short term. A longer study period is needed to determine the extent of individual response to increased exercise activity over a prolonged period.
  • Participant characteristics were relatively homogenous. Additional study using a wider variety and larger number of participants would make findings more relevant.

Additional References:

  1. Donnelly JE, Smith BK. Is exercise effective for weight loss with ad libitum diet? Energy balance, compensation, and gender differences. Exerc Sport Sci Review. 2005;33(4):169-74
  2. Stubbs RJ, Sepp A, Hughes DA, et al. The effect of graded levels of exercise on energy intake and balance in free-living women. Int J Obes Relat Metab Disord. 2002;26:866-9.
  3. King NA, Caudwell P, Hopkins M, et al. Metabolic and behavioral compensatory responses to exercise interventions: barriers to weight loss. Obesity (Silver Spring). 2007;15:1373-83.
  4. Haskell WL, Lee IM, Pate RR, et al. Physical activity and public health: updated recommendations for adults from the American College of Sports Medicine and the American Heart Association. Med Sci Sports Exerc. 2007;39(8):1423-34.