Alterations in Physical Activity Offset Changes in Energy Flux with Weight Change

Abstract

Energy flux, which reflects the rate of total daily energy expenditure (TDEE) and energy intake (EI), has been suggested to play an important role in the regulation of energy balance. PURPOSE: To examine differences in energy expenditure, energy intake and physical activity between young adults who lost, maintained or gained weight. METHODS: A sample 195 adults (52% male) between 21 and 35 years of age participating in an observational study provided valid data over a 2-year period. Anthropometric measurements, including fat mass and fat free mass obtained via dual x-ray absorptiometry, were taken every 3 months. In addition, participants wore a multi-sensor device for a period of 10 days at each measurement time to estimate TDEE, time spent in sedentary behavior (excluding sleep) (< 1.5 METs), time spent in light PA (1.5-3 METs) and in moderate-to-vigorous PA (MVPA > 3 METs). EI was calculated based on change in fat mass and lean mass and TDEE. A cutpoint of 5% change in body weight was used to stratify participants into a weight loss, weight maintenance and weight gain group. RESULTS: More than half (57%) of the study population maintained body weight, while 14% lost weight and 29% gained weight. There was no difference in baseline anthropometric measurements across weight-change groups after adjusting for sex. The weight loss group displayed an average weight loss of 6.9±3.4 kg and the weight gain group experienced an average increase of 7.1±3.6 kg over 2 years. The majority of weight change was due to change in body fat (79% and 82% in weight loss and weight gain, respectively). There was no significant difference in TDEE and EI at baseline across weight change groups and absolute TDEE and EI did not change significantly over the 2-year observation period in either weight change group (p≥0.17). Weight loss, however, was associated with a significant increase in MVPA (35±49 min/day; p<0.01), while MVPA decreased significantly in the weight gain group (-35±46 min/day; p<0.01). CONCLUSION: Results of this study indicate that TDEE and EI remain stable over time despite considerable changes in body weight and body composition. Weight gain, therefore, may be a natural response of the human body to maintain energy flux when physical activity is reduced. An increase in MVPA, on the other hand, appears to maintain TDEE at a lower body weight.