Study Spotlight: Caffeine and it's Influence on Metabolic Rate

By: Andrew Jagim

In support of our previous post on the benefits of caffeine for performance, we figured we would continue with the theme and discuss how caffeine can also provide some metabolic benefits as well.  Caffeine is labeled as a stimulant as it increases central nervous system activity and magnifies our sympathetic stimulatory response (i.e. increases adrenaline).   Because of this, caffeine can increase mental alertness, exercise performance and even boost our metabolic rate in addition to influencing the type of fuel (carbs vs. fats) being burned at any given time.  Researchers have specifically invested how big of a metabolic increase we experience following ingestion of differing amounts of caffeine and how it influences fuel utilization.

What did they do?

Researchers examined the acute effects of caffeine ingestion on metabolic activity and how if influences fuel utilization.  Specifically, the researchers conducted a series of 4 experimental trials under different conditions:

Trial 1: Subjects consumed 8mg/kg of caffeine and metabolic rate and various aspects of fuel utilization kinetics were assessed 3 hrs after ingestion and subsequently compared to placebo condition.

Trial 2: Subjects (both obese and non-obese) consumed 4 mg/kg of caffeine and were assessed in the same categories as previously mentioned.

Trial 4: Subjects ingested coffee in conjunction with a 700 calorie meal.

What did they find?

The researchers observed significant increase in metabolic activity in both caffeine conditions and this increase in metabolism occurred in both control and obese subjects. However, the control subjects also experienced a significant increase in plasma free-fatty acids suggesting an increase in fat mobilization and oxidation following consumption of caffeine.  When coffee was combined with the 700 calorie meal, a greater thermic effect of food was observed.

Take Home Message

The results of this study continue to provide evidence that caffeine can boost your metabolism. Generally, caffeine consumption will increase metabolic activity by 10-15% for 1-5 hrs post ingestion.  So, if your basal metabolic rate is 1,500 calories for example, you would burn an additional 150-225 calories after consuming coffee. Granted, keep in mind that if you add creamer, sugar etc. to your morning coffee you may quickly off-set any additional calorie burn from the caffeine. However, with that being said consuming coffee with a morning breakfast does appear to increase the thermic effect of the meal (the amount of calories you burn digesting/absorbing food.) so you do still experience some additional calorie expenditure from the caffeine even when food is co-ingested.  Also, caffeine appears to increase fat-utilization following ingestion however this may be limited to normal-weight individuals as states of obesity may interfere with the lipolytic effects.

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