1. Introduction
eating behaviors, weight loss
Multi-ingredient thermogenic supplements can acutely increase resting energy expenditure (REE) and subjective energy. However, less is understood about the effects of chronic consumption on body composition, metabolism, and subjective variables such as mood, sleep quality, and eating behaviors. Fifty-two healthy, exercise-trained participants (50% female; mean ± SD age: 23.5 ± 3.0 years; body fat percentage: 27.3 ± 8.0%) were randomized 2:2:1 to take a whey protein supplement alone (PRO; n = 20), in combination with a thermogenic supplement (PRO + FB; Use of dietary supplements, which are defined as orally administered products containing one or more dietary ingredients intended to supplement an individual’s diet, has grown in prevalence in the United States [A reduction in weight and/or fat mass is a frequently cited goal among active and athletic individuals, whether in pursuit of performance-related (e.g., increased efficiency), strategic (e.g., eligibility to compete in a certain weight class), or aesthetic goals (e.g., competing in aesthetically based sports such as bodybuilding) [Caffeine is a naturally occurring alkaloid compound that is commonly found in coffee, tea, and cocoa [Additional compounds commonly found in thermogenic formulations include “fat-burning” substances purported to promote weight loss. However, the mechanisms of these supplements—from increasing fat oxidation and impairing fat absorption to suppressing appetite and increasing energy expenditure—are less well studied and understood than those of caffeine. Such compounds include L-carnitine, conjugated linoleic acid (CLA), and traditional herbal supplements and plant extracts such as B-vitamins—water-soluble compounds naturally found in foods such as grain and seafood—play important roles in critical enzymatic reactions and metabolic pathways required to generate adenosine triphosphate (ATP) [The acute effects of caffeine and caffeinated multi-ingredient thermogenic supplements on variables such as REE, fat oxidation, and energy and mood-state in athletic individuals is well-documented [