Strength training is more effective than aerobic exercise for improving glycaemic control and body composition in people with normal-weight type 2 diabetes: a randomised controlled trial

Abstract

Aims/hypothesis: Type 2 diabetes in people in the healthy weight BMI category (<25 kg/m²), herein defined as 'normal-weight type 2 diabetes', is associated with sarcopenia (low muscle mass). Given this unique body composition, the optimal exercise regimen for this population is unknown.

Methods: We conducted a parallel-group RCT in individuals with type 2 diabetes (age 18-80 years, HbA_1c 47.5-118.56 mmol/mol [6.5-13.0%]) and BMI <25 kg/m²). Participants were recruited in outpatient clinics or through advertisements and randomly assigned to a 9 month exercise programme of strength training alone (ST), aerobic training alone (AER) or both interventions combined (COMB). We used stratified block randomisation with a randomly selected block size. Researchers and caregivers were blinded to participants' treatment group; however, participants themselves were not. Exercise interventions were conducted at community-based fitness centres. The primary outcome was absolute change in HbA_1c level within and across the three groups at 3, 6 and 9 months. Secondary outcomes included changes in body composition at 9 months. Per adherence to recommended exercise protocol (PP) analysis included participants who completed at least 50% of the sessions.

Results: Among 186 individuals (ST, n=63; AER, n=58; COMB, n=65) analysed, the median (IQR) age was 59 (53-66) years, 60% were men and 83% were Asian. The mean (SD) HbA_1c level at baseline was 59.6 (13.1) mmol/mol (7.6% [1.2%]). In intention-to-treat analysis, the ST group showed a significant decrease in HbA_1c levels (mean [95% CI] -0.44 percentage points [-0.78, -0.12], p=0.002), while no significant change was observed in either the COMB group (-0.35 percentage points, p=0.13) or the AER group (-0.24 percentage points, p=0.10). The ST group had a greater improvement in HbA_1c levels than the AER group (p=0.01). Appendicular lean mass relative to fat mass increased only in the ST group (p=0.0008), which was an independent predictor of HbA_1c change (beta coefficient -7.16, p=0.01). Similar results were observed in PP analysis. Only one adverse event, in the COMB group, was considered to be possibly associated with the exercise intervention.

Conclusions/interpretation: In normal-weight type 2 diabetes, strength training was superior to aerobic training alone, while no significant difference was observed between strength training and combination training for HbA_1c reduction. Increased lean mass relative to decreased fat mass was an independent predictor of reduction in HbA_1c level.

Trial registration: ClinicalTrials.gov NCT02448498.

Funding: This study was funded by the National Institutes of Health (NIH; R01DK081371).

Keywords: Body composition; Exercise; HbA1c; Normal weight.

Fig. 1

Participant flow chart. ^aUnable to continue exercise: unable to continue exercise, family illness, stopped exercising and withdrew. ^bUnwilling to participate: too busy, not convenient, cannot commit, do not want to participate. EMR, electronic medical record

Fig. 2

Contrast results from repeated ANOVA. Follow-up mean HbA_1c levels derived from a repeated measures ANOVA for the ITT group (n=186) (a) and PP group (n=107) (b). The points correspond to the estimated means from the repeated measures ANOVA model. *p<0.05 AER vs ST, **p<0.01 AER vs ST. The table within each plot shows the results of the pairwise comparisons. Error bars represent SEs