Strength training outperforms aerobic exercise in normal-weight type 2 diabetes patients

Patients with type 2 diabetes who are not overweight may benefit from strength-training exercise to help build muscle mass, a recent trial found.

Researchers in California conducted a parallel-group randomized controlled trial in patients with type 2 diabetes whose HbA1c levels ranged from 6.5% to 13.0% and whose body mass index was below 25 kg/m². Patients were recruited between November 2016 and December 2019 and assigned to nine months of strength training alone, aerobic training alone, or both combined, with exercise done at community fitness centers. The trial's primary outcome was absolute change in HbA1c level at three, six, and nine months, with changes in body composition at nine months as a secondary outcome. The results were published July 26 by Diabetologia.

One hundred eighty-six patients were included in the trial, 63 assigned to strength training, 58 assigned to aerobic exercise, and 65 assigned to both. Patients' median age was 59 years, 60% were men, and 83% were Asian; mean HbA1c level at baseline was 7.6%. Eighty-four percent of participants were taking glucose-lowering medications. An intention-to-treat analysis found that HbA1c levels decreased significantly in the strength-training group (mean, −0.44 percentage point [95% CI, −0.78 to −0.12 percentage point]; P=0.002) but not in the combined exercise group (−0.35 percentage point; P=0.13) or the aerobic group (−0.24 percentage point; P=0.10). Only the strength-training group had an increase in appendicular lean mass versus fat mass (P=0.0008); this was an independent predictor of change in HbA1c (beta coefficient, −7.16; P=0.01). Results were similar in an analysis that included only participants who completed at least 50% of the exercise sessions (38 in the strength-training group, 38 in the aerobic group, and 31 in the combined group). There were five adverse events during the trial, of which only one, in the combined group, was considered potentially associated with the intervention.

The researchers noted that their study had to be terminated early due to COVID-19 restrictions and that it was underpowered to obtain conclusive findings, among other limitations. They concluded that strength training alone was effective at reducing HbA1c levels in normal-weight patients with type 2 diabetes and superior to aerobic training alone and that combining the two types of exercise did not increase the benefit. “Normal-weight individuals with type 2 diabetes present with relative sarcopenia, and strength training to achieve increased lean mass relative to decreased fat mass plays an important role in glycaemic control in this population,” the authors wrote. “This study has important implications for the refinement of physical activity recommendations in type 2 diabetes by weight status.”