Abstract
Background. Type 2 diabetes, as the most common metabolic disease, is a chronic and progressive disorder that causes permanent complications and increases cardiovascular diseases, brain vessels, peripheral vessels, and mortality in affected people. This study, therefore, aimed to investigate the effect of eight weeks of interval training and caffeine supplementation on glycemic indices in men with type 2 diabetes.
Methods. The current research was a semi-experimental study. As a pilot research, 50 people were selected trough an available and targeted manner, among men with type 2 diabetes (with a history of more than one year) referring to Salamat and Sheikh Al-Rais Specialist clinics, Tabriz, Iran In the period of 2020-2021. 32 people met the inclusion criteria and entered into the study. Participants in the study were simple randomly divided into four homogenous groups of 8 including; Placebo, caffeine, exercise and exercise + caffeine were divided. Drug interventions and intermittent exercises were performed for 8 weeks. Blood samples were collected during two stages (pre-test and post-test) to measure serum levels of glucose, insulin, HbA1c and HOMA-IR index. The data were analyzed using repeated analysis of variance, Bonferroni post hoc and independent t tests at a significance level of 0.05.
Results. The results showed that the levels of the glucose, insulin, HbA1c, and HOMA-IR in the three intervention groups significantly decreased compared to those in the placebo group (P=0.001). Furthermore, the results of post hoc test showed that the combined group of interval training + caffeine, compared to the caffeine group, had double effects on the changes in studied indices (P=0.001).
Conclusion. A combination of interval training and caffeine supplementation may have been adopted as an effective method to improve and treat symptoms associated with type 2 diabetes.
Extended Abstract
Background
The prevalence of type 2 diabetes has steadily increased worldwide due to the increase in obesity rate. Therefore, insulin resistance (i.e., the impairment of insulin's ability to stimulate glucose uptake from surrounding tissues) has become one of the prominent features of this metabolic disorder. However, it is well-established that people with insulin resistance are usually diagnosed with a decrease in glucose transport, an increase in the concentration of free fatty acids in plasma, and a substrate metabolism disorder. Therefore, glucose homeostasis is like a closed feedback loop that supports the pancreatic cells, liver, and peripheral tissues including brain, muscle, and adipose. Insulin sensitivity, insulin function, and beta cell function have significant effects on carbohydrate, fat, and protein metabolism, and dysregulation of these factors leads to metabolic syndrome and diabetes.
Methods
This clinical trial was derived from a research plan approved by the Nutrition Sciences Research Center of Tabriz University of Medical Sciences.
The current research was a semi-experimental study. As a pilot research, 50 people were selected trough an available and targeted manner among men with type 2 diabetes (with a history of more than one year) referring to Salamat and Sheikh Al-Rais Specialist clinics, Tabriz, Iran In the period of 2021-2022. 32 people met the inclusion criteria and entered into the study. Then they were simple randomly assigned to four groups of eight people including three experimental groups (i.e., intermittent exercise, caffeine, and combined) and a control group.
The study subjects' height and weight were measured using a Seca digital scale and their body mass indices were calculated in order to evaluate their body composition. Their body fat percentages were also measured using Body Composition Analyzer. In addition, the subjects' daily diet was recorded using a 24-hour nutritional recall questionnaire in order to check the number of calories and the percentage of energy received from macronutrients.
Subjects in the supplement-receiving group were given one capsule containing 3 mg of caffeine per kg of the body weight on a daily basis, and those in the placebo group were given the same amount of dextrose.
The interval training program was carried out for eight weeks, three sessions per week, and each session lasted from 34 minutes (first weeks) to 58 minutes (last weeks). The intensity of the activity was performed with 70-85% of the reserve heart rate.
Blood samples were collected 24 hours before and after the implementation of the protocol by obtaining 5 ml of blood from the antecubital vein of the subjects' left arm, each time 8-10 hours after the overnight fasting.
The amount of fasting serum glucose was calculated by adopting enzyme colorimetric method based on the glucose oxidase reaction, while the amount of fasting serum insulin was calculated by employing ELISA method. Glycosylated hemoglobin (HbA1c) was measured using spectrophotometric method. Insulin resistance index was also calculated using the homeostasis model evaluation method (HOMA).
ANOVA with repeated measurements, Bonferroni's post hoc test, and independent t test were used to analyze the data and determine the differences among the study groups. All steps and statistical analyzes were performed at a significance level of α≤0.05 using SPSS version 22 statistical software.
Results
The mean and standard deviation of the demographic and physiological characteristics (i.e., age, weight, height, fat percentage, body mass index, and waist-to-hip ratio) of the studied groups are shown separately . There was a statistically significant difference in the values of individual characteristics such as weight (P=0.042), body mass index (P=0.036), waist-to-hip ratio (P=0.03), and body fat percentage (P=0.03). Differences were also observed among the studied groups in the post-study stage (P≤0.05).
According to the study results, serum levels of glucose, insulin, HbA1c and HOMA-IR were decreased significantly after two months of intervention in the caffeine + interval training group compared to the placebo group (P=0.001). Furthermore, a statistically significant decrease was observed between the interval training + caffeine group and the caffeine group in terms of the indices involved in insulin resistance (P≤0.05).
Conclusion
In sum, the adverse changes in indicators associated with diabetes may have been prevented by using a combination of eight weeks of caffeine supplementation and interval training in men with type 2 diabetes. Therefore, it was recommended that people with prediabetes, diabetes, and even hereditary background should use caffeine supplements in addition to interval training in order to prevent and reduce the adverse effects of diabetes.