Influence Of Sex Differences On Exercise-induced Hypoglycemia

PURPOSE: Previous studies have demonstrated that carbohydrate intake 30-60 min before exercise can cause exercise-induced hypoglycemia in men. However, there are sex differences in insulin secretion and skeletal muscle mass, which may cause sex differences in glucose metabolism during exercise. Exercise-induced hypoglycemia has not been directly compared between males and females. Therefore, we investigated the influence of sex on exercise-induced hypoglycemia. METHODS: The subjects were 12 men (age: 22.0 ± 2.3 years, height: 173.5 ± 4.5 cm, and body weight: 70.9 ± 7.9 kg) and 14 women in the early follicular phase (age: 24.1 ± 4.8 years, height: 158.1 ± 4.9 cm, and body weight: 55.5 ± 6.0 kg). Each subject consumed a 250 mL beverage containing 1.0 g·(kg body mass)-1·h-1 of glucose within 2 min, followed by 30 min of rest. Subsequently, they were cycled for 60 min at 70% VO2max. Blood glucose and serum insulin levels were measured 30 min before exercise (T-30), immediately before the start of exercise (T0), and at 15, 30, and 60 min during exercise (T15, T30, and T60). RESULTS: Blood glucose and serum insulin levels were significantly higher in women than in men at T60 (blood glucose, group: p = 0.06, time: p < 0.01, group × time: p < 0.05, T60: p < 0.01; insulin, group: p = 0.48, time: p < 0.01, group × time: p < 0.01, T60: p < 0.05). However, no significant sex differences were observed in blood glucose or serum insulin levels at T15 or T30, which are associated with exercise-induced hypoglycemia. Furthermore, a comparison of 8 men and 8 women who developed exercise-induced hypoglycemia (defined as blood glucose <70 mg/dL) revealed that the lowest blood glucose (at T15 or T30 points) was significantly lower in men compared to that in women (men: 59.4 ± 4.5 mg/dL, women: 64.8 ± 5.7 mg/dL, p < 0.05). The areas under the curve for serum insulin (T-30 to T0, T0 to T15, and T-30 to T60) were significantly higher in women than in men (p < 0.05). However, the overall changes in blood glucose and serum insulin levels over time from T-30 to T60 were similar for all participants. CONCLUSION: Our results suggest that sex differences exist in the extent of decline in blood glucose and the amount of insulin in individuals who experience exercise-induced hypoglycemia.