The Effect of Engaging in a Lifestyle Weight Loss Program on Adaptive Thermogenesis in Older Adults

Abstract

ObjectiveStudies in younger adults show that weight loss results in adaptive thermogenesis, a reduction in resting metabolic rate (RMR) beyond what is predicted by changes in body composition. However, whether adaptive thermogenesis occurs in response to weight loss in older adults is not as well documented. The objective of this analysis was to determine whether adaptive thermogenesis occurs in older adults engaging in a lifestyle weight loss program involving aerobic exercise training (AEX) and dietary caloric restriction (CR).MethodsOlder (65–79 yrs) sedentary men and women with obesity (BMI: 30–45 kg/m2) participated in a 20‐week study assessing the effects of adding CR to AEX on cardiorespiratory fitness and physical function outcomes. Participants were randomly assigned to CR+AEX (n=107) or AEX only (n=41). All participants engaged in the same treadmill walking program of 4 days/week for 30 minutes at 65–70% heart rate reserve. Baseline and post‐intervention RMR and body composition were measured with indirect calorimetry and dual‐energy x‐ray absorptiometry, respectively. Baseline measures of body composition, age, and sex were used to generate a linear regression equation to predict RMR. To determine metabolic changes resulting from the intervention, post‐intervention measures were applied to the same regression equation. Adaptive thermogenesis was calculated as the difference between predicted and measured RMR post‐intervention; a value <0 indicated the presence of adaptive thermogenesis.ResultsThe CR+AEX group lost more body weight (−8.9 ± 4.4 vs. −1.5 ± 3.5 kg, p<0.01) and fat free mass (FFM; −2.4 ± 2.2 vs. −0.5 ± 2.1 kg, p<0.01) compared with AEX. Measured RMR was similar in CR+AEX compared with AEX before (1365 ± 275 vs. 1378 ± 256 kcal/d, p=0.79) and after (1294 ± 259 vs. 1332 ± 252 kcal/d, p=0.42) the intervention. Adaptive thermogenesis was similar in CR+AEX compared with AEX (−23 ± 159 vs. −33 ± 189 kcal/d, p=0.73). There was large individual variability in the degree of adaptive thermogenesis in both groups (CR+AEX: −409 to 376 kcal/d; AEX: −534 to 359 kcal/d), which did not correlate with the individual degree of relative or absolute CR or to the individual amount of weight lost (all p>0.05).ConclusionsCompared with AEX alone, older adults engaging in weight loss by CR and AEX did not experience a greater decline in RMR beyond what was expected from changes in body composition. Since individual variability in adaptive thermogenesis was not related to amount of weight lost or CR, further research is needed to identify factors that cause adaptive thermogenesis in some older individuals.Support or Funding InformationNIH R01 HL093713 (BJN), NIA P30 AG021332, NIH T32 AG033534This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.