The thermic effect of sugar-free Red Bull: do the non-caffeine bioactive ingredients in energy drinks play a role?

Obesity (Silver Spring). 2015 Jan;23(1):16-9. doi: 10.1002/oby.20905. Epub 2014 Oct 8.


Objective: Consumption of energy drinks is increasing amongst athletes and the general public. By virtue of their bioactive ingredients (including caffeine, taurine, glucuronolactone, and B-group vitamins) and paucity of calories, sugar-free "diet" versions of these drinks could be a useful aid for weight maintenance. Yet little is known about the acute influence of these drinks, and specifically the role of the cocktail of non-caffeine ingredients, on resting energy expenditure (REE) and substrate oxidation. Therefore, the metabolic impact of sugar-free Red Bull (sfRB) to a comparable amount of caffeine was compared.

Methods: REE and respiratory quotient (RQ) were measured in eight healthy young men by ventilated-hood indirect calorimetry for 30 min baseline and 2 h following ingestion of 355 ml of either: sfRB + placebo, water + 120 mg caffeine, or water + placebo, according to a randomized cross-over design.

Results: sfRB and water + caffeine both increased REE to the same degree (+4%). Additionally, sfRB briefly increased RQ. Water + caffeine had no effect on RQ relative to water + placebo.

Conclusions: sfRB enhanced thermogenesis and marginally shifted RQ to favor carbohydrate oxidation. The stimulatory effects of sfRB on REE are mimicked by water + caffeine, indicating that the auxiliary ingredients do not influence this thermic effect. The metabolic effects of sfRB are primarily due to caffeine alone.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Animals
  • Body Weight / drug effects
  • Caffeine / pharmacology
  • Cattle
  • Cross-Over Studies
  • Energy Drinks*
  • Energy Intake / drug effects
  • Energy Metabolism / drug effects
  • Glucuronates / pharmacology*
  • Humans
  • Male
  • Plant Extracts / pharmacology
  • Rest
  • Taurine / pharmacology*
  • Thermogenesis / drug effects*
  • Vitamin B Complex / pharmacology*
  • Young Adult


  • Glucuronates
  • Plant Extracts
  • Vitamin B Complex
  • Taurine
  • glucuronolactone
  • Caffeine