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.

Inclusion criteria

• Young adult men and women between the ages of 18 and 35 years old.
• Participant is deemed by the investigator to be healthy and free of any physical limitations determined by physical activity readiness questionnaire (PAR-Q+) and medical and activity history questionnaire (MHQ).
• Participants will be required to be recreationally-active (defined according to American College of Sports Medicine standards of at least 150 minutes exercise per week and verified by information provided in the MHQ).
• Participant is willing to abstain from dietary supplementation throughout the duration of the study as indicated in the Informed Consent.
• Participant understands the study procedures and signs forms providing informed consent to participate in the study.

Exclusion criteria

• Inability to perform physical exercise, as determined by the PAR-Q+.
• Any "Yes" response in the PAR-Q+.
• History of hypertension, metabolic, hepatorenal, musculoskeletal, autoimmune or neurological disease, as determined by the MHQ.
• Regular consumption of greater than 250 mg per day of caffeine
• Currently taking thyroid, antihyperlipidemic, hypoglycemic, anti-hypertensive or androgenic medications.
• Taking any other nutritional supplement or performance-enhancing drug (determined from MHQ) that may interfere with the outcome variables of the study.
• Pregnancy (determined from MHQ).