The weather is getting colder and to many, cold weather is synonymous with a nice, steaming cup of coffee. In fact, we all have clients who cannot seem to function without their morning fix of caffeine. Which prompts the oft posed question, what are the effects of caffeine on a resting metabolic rate test? A look at the research reviewed by the American Dietetic Association can give us some insight.
In general, caffeine will cause a measurable increase in metabolic rate between 30 and 150 minutes after ingestion. The question of how much of an increase varies between the studies, likely due to the size and body mass of the subjects and the amount of caffeine consumed. For example, in healthy men, 10 oz of brewed coffee resulted in a mean increase of 7% – 11% (9-16 k/cal) in RMR for 1-3 hours after ingestion, while another similar study of women showed increases up to 24%. In a different study, lean and obese women were given four times that amount of caffeine, but in small servings throughout the day. They experienced an increase of 98 to 178 k/cal per day.
So without a doubt, caffeine does affect metabolic rate. Evaluating test results affected by caffeine ingestion is loaded with problems. The effect is highly dependent on dose and time since consumption, as well as body composition of the client and therefore is not a number that can be calculated and compensated for. This is precisely why KORR Medical Technologies and the ADA recommend a 4 hour abstinence from caffeine before performing an RMR test. If a client has ingested caffeine prior to a scheduled test, the ideal course of action is to reschedule.
Best Practice Methods to Apply to Measurement of Resting Metabolic Rate in Adults: A Systematic Review. Charlene Compher, et al. Journal of the American Dietetic Association Volume 106, Issue 6, Pages 881-903, June 2006.