The Effects Of A High-carbohydrate Versus A High-fat Shake On Metabolism And Glycemic Control When Used To Interrupt A 38-hour Fast

PURPOSE: Improving glycemic control and metabolic health is vital to reducing the incidence of chronic diseases such as obesity and insulin resistance. The primary aim of this study was to determine the impact of various fast-interrupting shakes on markers of glycemic control including glucose, β-hydroxybutyrate (BHB), insulin, glucagon, GLP-1, and GIP. METHODS: Twenty-seven normoglycemic sedentary adults (12 female, 15 male) with overweight or obesity completed all three conditions of this study (Body mass index = 31.2 ± 4.5 kg/m2, Age = 36.0 ± 13.3 years). One condition consisted of a 38-hour water-only fast, and the other two conditions repeated this, but the fasts were interrupted at 24 hours by either a high carbohydrate/low fat (HC/LF) shake - 70% glucose, 20% protein, 10% fat, or an isovolumetric and isocaloric low carbohydrate/high fat (LC/HF) shake - 70% fat, 20% protein, 10% glucose. RESULTS: The water only fast resulted in 135.3% more BHB compared to the HC/LF condition (p < 0.01) and 69.6% more compared to the LC/HF condition (p < 0.01). Conversely, the LC/HF condition exhibited a 38.8% higher BHB level than the HC/LF condition (p < 0.01). Area under the curve (AUC) for glucose was 14.2% higher in the HC/LF condition than in the water condition (p < 0.01) and 6.9% higher compared to the LC/HF condition (p < 0.01), with the LC/HF condition yielding 7.8% more glucose than the water condition (p < 0.01). At the 25-hour mark, insulin and glucose-dependent insulinotropic polypeptide (GIP) were significantly elevated in the HC/LF condition compared to the LC/HF condition (p < 0.01 and p = 0.02, respectively) and compared to the water condition (p < 0.01). Furthermore, insulin, GLP-1, and GIP were increased in the LC/HF condition compared to the water condition at 25 hours (p < 0.01, p = 0.015, and p < 0.01, respectively). Glucagon concentrations at 25 hours decreased in the HC/LF group compared to the LC/HF condition (p < 0.01). By the 38-hour time point, no differences were observed among the conditions for any of the analyzed hormones. CONCLUSIONS: While a LC/HF shake does not mimic a fast completely, it does preserve some of the metabolic changes including elevated BHB and glucagon, and decreased glucose and insulin compared to a HC/LF shake, implying a potential for improved metabolic health and reduced risk of chronic disease. Funded through student mentoring department funds