Relative Changes In Diet And Neat In Response To Initiating A Walking Exercise Program

Abstract

Variability in the efficacy of structured exercise to achieve targeted levels of weight loss or maintenance appears to be primarily due to individual differences in behavioral responses that increase energy intake (EI) or decrease non-exercise activity thermogenesis (NEAT). However, the relative importance of each type of compensatory behavior remains incompletely characterized. PURPOSE: To quantify and compare changes in EI and NEAT that occur when women initiate a structured exercise program. METHODS: Previously sedentary women (n=98, 35.9±6.1 y, 75% white non-Hispanic, 29.8±8.2 kg/m2) completed an 8-week exercise-only intervention with the goal of achieving 150 min/week of moderate intensity walking. ActiGraph GT3X+ monitors were worn during waking hours for 1-week at baseline and throughout the intervention to measure exercise energy expenditure (ExEE) and changes in NEAT (kcal/d). Changes in EI (kcal/d) were measured via the National Cancer Institute’s ASA24 program on three randomly selected days at baseline and six days during the intervention. RESULTS: The exercise intervention directly increased ExEE by a mean of 103.3 kcal/d above baseline values. Reflecting the observation that 50% of women reported an intention to diet during the exercise intervention, there was a significant decrease in average EI (-185.3±558.1 kcal/d, p<.01), but no change in relative macronutrient intake (p>.35 for all). However, 27.6% of women reported increases in EI greater than their ExEE, including 20.4% of intended dieters. Modest average decreases in NEAT (-46.4±69.5 kcal/d, p<.01) were observed although 9.2% of women had decreases which exceeded their increased ExEE. Overall, combined changes in EI and NEAT totally offset ExEE for 28.6% of women. A smaller percentage of overweight and obese women (23.1%) than healthy weight women (39.4%) had compensatory changes exceeding ExEE, although these differences were not statistically significant (p=.09). CONCLUSIONS: Among women initiating a structured exercise program, changes in total daily EI are of greater magnitude than changes in NEAT. For approximately a quarter of participating women, compensatory behavioral changes appear to totally offset the additional ExEE. Supported by NHLBI-1R21HL113742-01