The combined effect of high-intensity intermittent training and vitamin D supplementation on glycemic control in overweight and obese adults

Abstract

High-intensity intermittent training (HIIT) has been shown to reduce the risk of chronic conditions including the development of type 2 diabetes mellitus (T2DM). Independently, a low vitamin D status has also been linked to the prevalence of T2DM. The aim of this study was to investigate if there was a synergistic metabolic effect of HIIT and vitamin D supplementation on glycemic control. A total of 20 male and female participants (age, 34 ± 9 year; BMI, 31.4 ± 2.8 kg·m^-2 ) completed 6 weeks HIIT, and were randomized to ingest 100 μg·day^-1 of vitamin D₃ or placebo. Response to an oral glucose tolerance test (OGTT) was determined at baseline and at 72 h postintervention. Glucose tolerance was improved as a result of the HIIT intervention, shown through a reduction in glucose and insulin concentrations during the OGTT, accompanied by a decrease in glucose (829 ± 110 to 786 ± 139 mmol·h^-1 ·L^-1 ; P = 0.043) and insulin (8101 ± 4755-7024 ± 4489 mU·h^-1 ·L^-1 ; P = 0.049) area under the curve (AUC). Supplementation increased 25-hydroxyvitamin D₃ concentration by 120% to a sufficiency status (P < 0.001). However, the consumption of vitamin D₃ seemed to attenuate the glucose response during an OGTT. Triglyceride content was lowered following the intervention (P = 0.025). There was no effect of the intervention on insulin sensitivity (IS) indices: ISI_Matsuda and HOMA-IR. Our findings demonstrate that HIIT improves glucose tolerance in nondiabetic overweight and obese adults; however vitamin D₃ supplementation did not proffer any additional positive effects on the measured indices of metabolic health.

Keywords: glucose tolerance; high-intensity intermittent training; vitamin D.

Figure 1

Plasma 25(OH)D₃ concentrations at baseline and postintervention for the placebo group and the vitamin D group. *Denotes a significant condition (vitamin D supplement vs. placebo)‐by‐time (pre to post) interaction effect; P < 0.05.

Figure 2

Response to a 75 g OGTT at baseline and 72 h postintervention for all participants: glucose (A) and insulin (B) concentrations, and split for the placebo and vitamin D supplement group: glucose (C) and insulin (D) concentrations. *Denotes a significant difference in the oral glucose tolerance test between pre‐ and postinterventions; P < 0.05.