Dose-Dependent Effects of Exercise and Diet on Insulin Sensitivity and Secretion.

PURPOSE: A single bout of aerobic exercise increases insulin sensitivity the next day. The effects of exercise on insulin secretion, the role of exercise-induced energy deficit, and possible dose-response relationships are not well understood. This study aimed to evaluate insulin sensitivity and insulin secretion after progressively greater negative energy balance induced by exercise or diet. METHODS: Acute energy deficits (20% or 40% of weight maintenance needs) were induced by a single day of aerobic exercise (cycling at moderate intensity, n = 13) or dietary restriction (n = 19) in healthy men and women (age, 26 ± 2 yr; body mass index, 21.8 ± 0.5 kg·m). Intravenous glucose tolerance tests in conjunction with minimal modeling were performed the next morning, and blood samples were collected for 3 h to measure glucose and insulin concentrations. RESULTS: Insulin sensitivity increased linearly after exercise-induced energy deficits (P = 0.007) but did not change after equivalent diet-induced energy deficits (P = 0.673). Acute insulin response decreased after both exercise (P < 0.001) and dietary restriction (P = 0.005). The disposition index and glucose effectiveness were not affected by exercise (P = 0.138 and 0.808, respectively), but both decreased after 40% dietary restriction (P = 0.048 and 0.002, respectively). CONCLUSIONS: These results indicate that insulin sensitivity and insulin secretion are related to exercise energy expenditure, albeit in a different fashion (insulin sensitivity increases linearly, whereas insulin secretion drops to a nadir with a low exercise dose and does not decrease further). These changes cannot be replicated by equivalent energy deficits induced by dietary restriction, suggesting that exercise and diet have different effects on the mechanisms regulating glucose homeostasis. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03264001.

Lipoprotein Subclass Profile after Progressive Energy Deficits Induced by Calorie Restriction or Exercise.

Weight loss, induced by chronic energy deficit, improves the blood lipid profile. However, the effects of an acute negative energy balance and the comparative efficacy of diet and exercise are not well-established. We determined the effects of progressive, acute energy deficits (20% or 40% of daily energy requirements) induced by a single day of calorie restriction (n = 19) or aerobic exercise (n = 13) in healthy subjects (age: 26 ± 9 years; body mass index (BMI): 21.8 ± 2.9 kg/m²). Fasting plasma concentrations of very low-, intermediate-, low-, and high-density lipoprotein (VLDL, LDL, IDL, and HDL, respectively) particles and their subclasses were determined using nuclear magnetic resonance. Total plasma triglyceride and VLDL-triglyceride concentrations decreased after calorie restriction and exercise (all p ≤ 0.025); the pattern of change was linear with an increasing energy deficit (all p < 0.03), with no evidence of plateauing. The number of circulating large and medium VLDL particles decreased after diet and exercise (all p < 0.015), with no change in small VLDL particles. The concentrations of IDL, LDL, and HDL particles, their relative distributions, and the particle sizes were not altered. Our data indicate that an acute negative energy balance induced by calorie restriction and aerobic exercise reduces triglyceride concentrations in a dose-dependent manner, by decreasing circulating large and medium VLDL particles.