In older women with overweight or obesity, a minimal energy deficit induced by a joint aerobic and resistance exercise program was accompanied by metabolic adaptation at the level of resting metabolic rate in a 32-week study by Cátia Martins, PhD, and colleagues that was published in Obesity.

“Weight loss induced by diet alone, and diet plus exercise, is accompanied by metabolic adaptation,” explains Dr. Martins. “Very few studies have investigated metabolic adaptation following exercise alone, and there are none in older women. Resistance training is recommended, in addition to aerobic exercise, particularly in this patient group, to try to minimize the loss of lean tissue that accompanies aging. This was the rationale for our study.”

Assessing Metabolic Adaptation in Older Women

The study included 80 women aged approximately 65 (64 White participants) who had an average BMI of 30 kg/m2 and an average maximum aerobic capacity of 23.6 (4.7) mL/kg/min. The women performed aerobic and resistance training during 32 weeks and had their body weight/composition and resting metabolic rate measured at baseline, week 16, and week 32.

By week 16, following a 640-kcal/week energy loss (-0.7 [2.6] kg of weight loss), a significant metabolic adaptation of -59 (±136) kcal/day was observed (P=0.002) across study participants. When considering the 53 women for whom there was complete data, metabolic adaptation was seen at both week 16 and week 32. At week 16, there was a metabolic adaption of -64 (±129) kcal/day (P=0.001), which reached -94 (±127) kcal/day by week 32 (P<0.001; Table), demonstrating a significant increase in metabolic adaptation between weeks 16 and 32 (-30 [85]; P=0.013). No significant differences in metabolic adaptation, however, were observed between women who lost weight and those who did not at week 16 (-55 [111] kcal/d vs -57 [153] kcal/d, respectively) and at week 32 (-72 [120] vs -99 [132] kcal/d, respectively).

Metabolic adaptation at week 16 and week 32 was predicted by race, age, baseline fat-free mass, resting metabolic rate, and change in net oxygen consumption of walking, with respiratory quotient also predictive at week 16 but not at week 32. Overall, Dr Martins and colleagues found that the lower the resting metabolic rate and fat oxidation at baseline, and the larger the increase in net maximum oxygen consumption after different exercise tasks, the greater the metabolic adaptation. This finding did not change when different activities were assessed (ie, walking with inclination, steps, or carrying a load).

“Despite aerobic and resistance exercise in older women with overweight or obesity being associated with metabolic adaptation at the level of resting metabolic rate, even when a minimal energy deficit is induced, this combined approach should continue to be recommended in this population,” Dr. Martins says.

Exercise Is Medicine

“Considering that exercise training can have an effect on metabolic adaptation, even after 6 months of training, but that energy expenditure is elevated for at least 22 hours following an exercise bout, these results could be interpreted to further support the concept that exercise is medicine that should be administered regularly,” wrote Dr. Martins and colleagues.

Dr. Martin notes that the study findings warrant further exploration in older women with overweight and obesity, adding that future research is also needed to confirm these findings in other populations, including men, different age groups, and people with different BMIs, “after controlling for energy balance status and for changes in the anatomical and molecular composition of fat-free mass.”