The Energy “Gap” and Risk of Weight-Loss Relapse: Differences in Self-Reported vs Measured Physical Activity

Introduction Relapse in the first 3-5 years following weight loss is a common problem in obesity management (Ross, 2009). The extent to which physiological (Jackman et al., 2008) vs behavioural adaptations contribute to weight loss relapse is not clearly understood. Moreover, there is some indication that an ‘energy gap’ or leading to positive energy balance and weight regain (Ross et al., 2000) may be related to lower levels of physical activity. The present study was designed to identify measurable differences in energy metabolism and substrate utilization (both at rest and during exercise, respiratory exchange and maximal rate of fat oxidation during exercise, Fatmax), as well as differences in self-reported energy and nutrient intake, reported and measured physical activity energy expenditure, in weight-stable (WS) and reduced-obese (RO) women, matched for body mass index and age.

Methods In a convenience sample of 44 women, body mass index, waist circumference, body composition (BIA), energy intake and nutrient intake, physical activity (Actigraph GT3X), and energy metabolism (resting respiratory exchange ratio and Fatmax) were measured. Questionnaires related to family history, demographics, physical activity (PA, Global Physical Activity Questionnaire), and eating and dieting behaviour were administered.

Results Mean age was 38 +/- 11 yrs and mean BMI was 24 +/- 2 kg/m². No significant differences were found between the RW subjects and the WS group for weight, waist circumference, fat-free-mass (FFM) or body fat percentage. Group were different for highest adult weight (P = 0.00028), total weight lost and percent body weight lost (P < 0.00001). Groups were also similar with respect to dietary energy intake, resting energy expenditure and maximal rates of fat oxidation during exercise. Measured physical activity was not different between groups, however, self-reported moderate PA (270 vs 113 min/wk; P = 0.02) was higher in the RW group.

Discussion Eating behaviour, energy metabolism, and fat oxidation appear to remain unperturbed in women who experience reductions in body weight of 14+/- 5.4% or less. However, the RW women over-reported moderate PA by more than 100 min on average per week. This finding suggests that reduced weight women are at risk of weight regain due to errors in perception related to levels of physical activity, rather than weight loss-induced changes in physiology.

References Ross R. (2009). CMAJ, 180, 997-998. Jackman MR, Steig A, Higgins JA, Johnson GC, Fleming-Elder BK, Bessesen DH, MacLean PS. (2008). Am. J. Physiol. Regul. Integr. Comp. Physiol, 294, R1117–R1129. Ross R, Dagnone D, Jones PJ, Smith H, Paddags A, Hudson R, Janssen I. (2000). Ann Intern Med 2000, 133, 92-103.