Acute Effects of Fitness Drink Formulas on Energy Expenditure and Fat Metabolism

Thermogenic fitness drinks containing \~200mg of caffeine have been reported to accelerate the metabolism, increase energy, and consequently promote increased fat oxidation. However, determination of the efficacy of lower caffeine concentrations may provide additional options for individuals with preferences for reduced caffeine intake. Therefore, the aim of this study was to evaluate different fitness drink formulas containing a total of 100mg and 140mg of caffeine on the physiological response at rest and to exercise. This study utilized a randomized, double-blind, placebo-controlled design. All participants completed three testing visits during which they consumed the placebo, the 100mg caffeine formula, and the 140mg caffeine formula. Blood samples, blood pressure, heart rate, resting energy expenditure, substrate oxidation, and neurocognitive assessments were collected at baseline and repeated 30, 60, and 90 minutes post-ingestion. Immediately following the last cognitive assessment, a maximal graded exercise test with gas analysis was conducted on a cycle ergometer to evaluate physical performance and maximal fat oxidation during exercise as well as the physiological response prior to and following exercise.