Energy Drinks Increase Resting Metabolic Rate, But Do Not Influence Energy Expenditure During Exercise

Ever wondered, whether the drink that was once rumored to contain "taurine from bull sperm" and similar fashionable "energy drinks" are of any use? Well, a recent study (Nienhuesser. 2011) coming from an international team of scientists showed that the consumption of each and every of the three energy drinks used in this study lead to a statistically significant increase in resting metabolic rate (RMR).

[...] in a randomly assigned cross-over design, the subjects consumed 473 ml of one of three commercially available energy drinks or a placebo and then RMR and RER [respiratory exchange ratio; i.e. a measure of the relative amount of fat/carbs that is used as fuel] were measured 1 hour later.  The subjects then engaged in 15 minutes of treadmill exercise at 50% of V02max, during which RER and oxygen consumption (VO2) were measured. RMR was not changed by placebo, but increased (P<0.05, means ± se) above baseline by 10 ± 2.5%, 15.0 ± 2.9%, and 15.3 ± 2.9%, following Energy Drink One, Energy Drink Two, and Energy Drink Three (respectively) [...]

In view of the stimulating effect, some of the ingredients (cf. Table 1) of these chemical containing beverages exhibit, these results do not come as a surprise.

Table 1: Listing of ingredients according to Nienhuesser. 2011

What may be surprising, however, is that the study results suggest that - at least from a "calorie expenditure" point of view - the consumption of an energy drink before exercise appears to be less effective than drinking it after exercise or at your desk at the office...