Comparison of the effect of submaximal exercise with and without caffeine consumption on alpha-amylase, leptin, glycemic indices and energy intake in obese and overweight people

     The aim of this study was to compare the effects of maximal exercise with and without caffeine supplementation on serum alpha-amylase, blood glucose, insulin, leptin, and energy intake in overweight or obese individuals.  This crossover study was conducted on 16 overweight or obese male and female volunteers aged over 18 years with a body mass index (BMI) > 25 kg/m2. Participants were randomly assigned into two conditions: maximal exercise with caffeine supplementation and maximal exercise without placebo supplementation. Participants received a dose of 200 mg caffeine capsule and starch powder and then performed 30 minutes of submaximal exercise at 60% of HRR. Blood samples were collected before and after caffeine supplementation and following exercise. The data were analyzed using repeated-measures ANOVA. caffeine increased blood glucose, insulin, and serum alpha-amylase (p < 0.05). Exercise significantly decreased serum alpha-amylase, insulin and blood glucose levels and increased leptin levels (p < 0.05). The change in insulin and blood glucose levels in response to exercise were greater with caffeine supplementation than with placebo (p < 0.05). However, caffeine had no significant effect on leptin levels or its response to exercise (p > 0.05). Although caffeine affected metabolic responses to exercise, it has no effect on appetite hormone leptin and subsequent food intake. Energy intake seemingly increases following exercise regardless of caffeine consumption, which should be considered in weight management.