Effects of Low-Carbohydrate versus Mediterranean Diets on Weight Loss, Glucose Metabolism, Insulin Kinetics and β-Cell Function in Morbidly Obese Individuals

Abstract

Low-calorie Mediterranean-style or low-carbohydrate dietary regimens are widely used nutritional strategies against obesity and associated metabolic diseases, including type 2 diabetes. The aim of this study was to compare the effectiveness of a balanced Mediterranean diet with a low-carbohydrate diet on weight loss and glucose homeostasis in morbidly obese individuals at high risk to develop diabetes. Insulin secretion, insulin clearance, and different β-cell function components were estimated by modeling plasma glucose, insulin and C-peptide profiles during 75-g oral glucose tolerance tests (OGTTs) performed at baseline and after 4 weeks of each dietary intervention. The average weight loss was 5%, being 58% greater in the low-carbohydrate-group than Mediterranean-group. Fasting plasma glucose and glucose tolerance were not affected by the diets. The two dietary regimens proved similarly effective in improving insulin resistance and fasting hyperinsulinemia, while enhancing endogenous insulin clearance and β-cell glucose sensitivity. In summary, we demonstrated that a low-carbohydrate diet is a successful short-term approach for weight loss in morbidly obese patients and a feasible alternative to the Mediterranean diet for its glucometabolic benefits, including improvements in insulin resistance, insulin clearance and β-cell function. Further studies are needed to compare the long-term efficacy and safety of the two diets.

Keywords: Mediterranean diet; beta cell function; glucose tolerance; high protein diet; insulin clearance; insulin secretion; insulin sensitivity; obesity; weight loss intervention.

Figure 1

Study design. BIA, bioimpedance analysis; OGTT, oral glucose tolerance test.

Figure 2

Insulin secretion rate during a 75-g OGTT (left panel) and insulin secretion rate against plasma glucose levels (right panel) in morbidly obese individuals before (dotted lines) and after (continuous lines) a 4-week low-carbohydrate diet (red lines) or Mediterranean diet (blue lines). Thick lines indicate mean and shaded areas indicate SEM.