Influence Of A Four Week Energy Drink Intervention On Glucose Regulation In Healthy Sedentary Individuals

Abstract

Energy drinks were originally designed for active sportsmen. However, they are also widely used by inactive people. PURPOSE: To investigate the effect of 4 weeks energy drink consumption on whole body and peripheral insulin sensitivity, and metabolism in sedentary individuals. METHODS: Twelve healthy, physically inactive participants with a sporadic consumption of energy drinks (5 males and 7 females, 26 ± 6 yrs and BMI = 21.7 ± 1.5) underwent a 4 week energy drink supplementation (on average 760 ml). This increased their carbohydrate intake by 2.1 ± 0.2 g/kg body weight. Participants were instructed to maintain and record their usual diet before, during and after the intervention. Pre- and post-test measures were indirect calorimetry, fasting blood glucose (immobilized enzymatic assay) and insulin (ELISA), body composition (DXA scan), and a muscle biopsy one hour after 75 g glucose ingestion (Western blot). Post-tests were carried out 32 hours after the last beverage was consumed. RESULTS: There was a trend for an increase in total body weight (65.5 ± 9.6 vs. 66.6 ± 10.5 kg, p = 0.079, hp2 = 0.254). Fat mass increased significantly (15.7 ± 5.1 vs. 16.8 ± 4.9 kg, p = 0.012), lean mass did not change (2.58 ± 0.57 vs. 2.58 ± 0.58 kg). Fasting respiratory exchange ratio (RER) increased significantly (0.75 ± 0.09 vs. 0.87 ± 0.08, p = 0.039) as did fasting plasma glucose (4.81 ± 0.40 vs. 5.10 ± 0.35 mmol/l, p = 0.012). There was a strong trend towards an increase in fasting plasma insulin (5.06 ± 1.75 vs. 6.40 ± 1.46 mU/l, p = 0.089, hp2 = 0.262). The homeostatic model assessment (HOMA2) of insulin sensitivity was decreased (156 ± 46 vs. 126 ± 30%, p = 0.057, hp2 = 0.316) and there was a trend towards an increase in insulin resistance (0.69 ± 0.18 vs. 0.84 ± 0.19, p = 0.072, hp2 = 0.288). Steady state beta cell function was unaltered (78.4 ± 26.6 vs. 82.1 ± 20.8%). Muscle markers of the main metabolic pathways were not significantly altered (FH, 3985 ± 1487 vs. 3134 ± 1703 AU, GAPDH 2118 ± 626 vs. 1840 ± 671 AU, ACC 5053 ± 2983 vs. 4070 ± 2380 AU). Insulin signalling related GSK-3a/b phosphorylation was significantly reduced (2405 ± 743 vs. 1838 ± 736 AU, p = 0.049). CONCLUSION: Healthy sedentary subjects who were given a commonly consumed amount of energy drinks for 4 weeks, worsened their glucose regulation, fat oxidation and fat mass.