Isolated or combined effect of aerobic exercise and diet on cortisol levels in patients with type 2 diabetes: preliminary results from a randomized control trial.

Abstract

Introduction. Cortisol is a glucocorticoid hormone essential in regulating metabolismand the stress response, directly impacting blood glucose levels. In people with type 2diabetes mellitus (T2DM), cortisol levels are often elevated, which exacerbates insulinresistance and poor glycemic control. The combination of overweight and obesity canintensify this dysfunction. Interventions such as physical exercise and diet have beenshown to influence cortisol levels, but the specific effects of their combination in thispopulation require further research. Therefore, this study aimed to investigate theisolated or combined effects of two different exercise programs and a dietaryintervention on cortisol levels in adults with T2DM.Methods. Thisis a randomized controlled trial from the APETEX and ENTRENOX projectsinvolving 110 patients (54 women) with T2D (age, 56.78 ± 6.0 years; body mass index,32.66 ± 5.4 kg/m²). The exercise program lasted 12 weeks with 3 sessions per week andincluded 2 options: high-intensity interval training (HIIT) consisting of 10×1 intervalscycling at 90% of maximum power, or moderate-intensity continuous training (MICT)consisting of continuous cycling at 10% above the first ventilatory threshold for 50minutes. The dietfactor had 2 levels: participants who received the diet, which consistedof 20-minute counselling sessions by an experienced nutritionist every 2 weeks for 12consecutive weeks, and controls (no diet). Therefore, participants were distributed intosix groups: HIIT, MICT, diet, HIIT+diet, MICT+diet, and a control group (inactive and nodiet). Blood samples were collected from participants at baseline and at 90’ of the oralglucose tolerance test (OGTT) before and after completing the intervention, and serum cortisol levels were analysed using the Alinity CI system (Abbott Laboratories, Abbott Park, Illinois). A mixed factorial ANOVA 3x2x2 was applied with Bonferroni post hoc comparisons. Results and Conclusions. There was a time*diet interaction (η2p = 0.049; p = 0.047).Regarding the intervention groups, only the group following the diet showed a significant difference in basal cortisol levels, with these levels decreasing after the intervention (p < 0.005). There is no time*diet*exercise interaction in cortisol levels at 90’ of OGTT and they do not show significant changes. Dietary intervention leads to a decrease in basal cortisol levels, with no differences observed based on exercise in patients with T2DM. This suggests that modifying dietary habits could be an effectivestrategy for reducing cortisol levels and thereby achieving better insulin resistance andglycemic control.