The effects of aerobic exercise and diet on glycemic control in people with type 2 diabetes mellitus: A randomized controlled trial

Abstract

INTRODUCTION: Aerobic exercise has traditionally been the main lifestyle strategy, alongside diet, for the management ofobesity and type 2 diabetes mellitus (T2DM). Nonetheless, controversy remains about the best therapeutic tool for glycemic control. So, the aim of this study was to compare the effects of aerobic exercise, diet, and the combination of both onglycemic control in people with T2DM.METHODS: A total sample of 130 adults (n=64 females; 55.7±7.1 years; Body Mass Index=33.1±5.4 kg/m2) with obesityand T2DM were randomized into six groups: High-Intensity Interval Training (HIIT) (n=22), HIIT+Diet (n=25), ModerateIntensity Continuous Training (MICT) (n=21), MICT+Diet (n=20), Diet Group (n=21), and Control Group (CG) (n=21). The 12-week training consisted of three sessions per week: HIIT included 10×1 intervals pedaling at 90% of peak power output,and MICT consisted of continuous pedaling at 10% above the first ventilatory threshold for 50 minutes. Diet consisted of anindividualized diet with a calorie deficit of 300 kcal. Fasting blood samples were taken and glucose, insulin, and glycosylated hemoglobin (HbA1c%) were analyzed. The homeostatic model assessment for insulin resistance (HOMA-IR) wascalculated. Finally, a 3-hour oral glucose tolerance test (OGTT) was performed to determine the area under the glucosecurve (AUGC) by the trapezoidal method. To examine the intervention effect, a 3x2x2 mixed ANOVA with Bonferroni’s posthoc was used.RESULTS: No differences were found between groups at the baseline (p>0.05). A main effect of time (F(1,123)=26.37,p<0.001, ηp2=0.18) and a time x diet interaction were observed for HbA1c (F(1,123)=15.84, p<0.001, ηp2=0.11), with differences between baseline and the end of intervention in the groups with diet (p<0.001). Main effects of time (F(1,123)=11.14,p=0.001, ηp2=0.08) and exercise (F(2,123)=3.47, p=0.034, ηp2=0.05) were observed for HOMA-IR, with differences between HIIT and CG (p=0.039). A main effect of time (F(1,123)=20.23, p<0.001, ηp2=0.14) and significant interactions of timex diet (F(1,123)=18.44, p<0.001, ηp2=0.13) and time x exercise (F(2,123)=4.06, p=0.020, ηp2=0.06) were observed forAUGC, with differences between baseline and the end of intervention in HIIT group (p<0.001) and groups with diet(p<0.001), and differences between diet and non-diet groups at the end of intervention (p=0.038). MICT only showedpositive results when combined with diet (p<0.05).CONCLUSION: HIIT and caloric restriction are the best therapeutic tools for the management of glycemic control in patients with T2DM, especially when combined. In fact, it has been suggested that the combination of diet and high-intensity exercise improves pancreatic function and body composition, leading to improved glucose metabolism. Thus, we recommended that trainers and exercise professionals use HIIT and diet as the main strategy for the treatment of T2DM.