A Randomized Study to Examine the Ability of a Caffeine-Based Energy Drink to Impact Energy Expenditure, Fat Oxidation, and Cognitive Performance

<b>Objectives</b>: This study evaluated the effects of acute and 28-day supplementation with a caffeine-based energy drink on energy expenditure, fat oxidation, and cognitive performance. <b>Methods</b>: In a double-blind, placebo-controlled trial, 33 males and 27 females (27 ± 8 years, 26.7 ± 2.2 m/kg²) consumed a caffeinated energy drink (200 mg; CAF) or placebo (PLA) for 28 days. Indirect calorimetry assessed energy expenditure and fat oxidation at 0, 30, 60, 90, and 120 min after ingestion on day 1 and 28. Cognition assessments (Dynavision reaction, Serial Sevens, Trail Making Test A (TMT-A) and B (TMT-B)) were performed at 0, 60, and 120 min. <b>Results</b>: On day 1, CAF demonstrated higher energy expenditure vs. PLA at 30 (<i>p</i> = 0.011), 60 (<i>p</i> = 0.001), 90 (<i>p</i> = 0.002), and 120 min (<i>p</i> < 0.001). On day 28, expenditure remained higher at 30 (<i>p</i> < 0.001), 60 (<i>p</i> = 0.019), and 90 min (<i>p</i> = 0.003). Comparing day 28 to day 1, CAF maintained greater energy expenditure at baseline (<i>p</i> = 0.031) with trends at 30 (<i>p</i> = 0.057) and 90 min (<i>p</i> = 0.051). Fat oxidation was greater with CAF only on day 1 at 60 (<i>p</i> = 0.019), 90 (<i>p</i> = 0.006), and 120 min (<i>p</i> = 0.012). On day 28, CAF showed more correct Dynavision hits (60, <i>p</i> = 0.002; 120, <i>p</i> = 0.003) and fewer misses (60, <i>p</i> = 0.003; 120, <i>p</i> = 0.005) vs. PLA. Faster reaction time occurred in CAF at 120 min on day 1 (<i>p</i> = 0.028), while serial subtraction showed trends toward higher counts in CAF (day 1: <i>p</i> = 0.079; day 28: <i>p</i> = 0.059). On day 28, CAF increased perceived focus and energy at 60 and 120 min (focus: <i>p</i> = 0.012, <i>p</i> = 0.026; energy: <i>p</i> = 0.005, <i>p</i> = 0.029). Alternatively, a trend for slower TMT-A performance emerged in CAF at 60 min on day 28 (<i>p</i> = 0.075), resulting in PLA having faster times across day 28 vs. day 1 comparisons (<i>p</i> = 0.033). <b>Conclusions</b>: Acute energy drink consumption enhances energy expenditure, fat oxidation, and some cognitive measures, while 28-day use sustains energy expenditure and select cognitive benefits.