How Does Caffeine Affect My RMR?

America loves coffee. Over half of America’s adult population relies on that heady combination of aroma and caffeine to jump start each day. But what exactly does that first cup o’ joe do to your metabolism?

We decided to find out it by running some pre-coffee and post-coffee resting metabolic rate (RMR) tests on ourselves!


To test this out, Elaine:

  1. Ran two regular, fasted, RMR tests to establish a baseline
  2. Chugged a Starbucks grande cold brew with no cream or sugar
    • This is roughly equivalent to 200 mg of caffeine
  3. Waited 45 minutes after which 99% of the ingested caffeine should have been absorbed
  4. Ran three more RMR tests to measure the changes

All told, our simple testing procedure took roughly two and a half hours.

Elaine doing her 5th RMR test

Here are Elaine’s results:

Time Resting Metabolic Rate Heart Rate
08:34 AM 1598 68
08:49 AM 1627 68
Drink Coffee!
09:53 AM 1858 61
10:13 AM 1930 64
10:33 AM 1886 67

Elaine's results

On average, Elaine's metabolism increased by about 17% after drinking the coffee!

For any individual, the magnitude of the impact of the caffeine on RMR will vary depending on:

  • Dosage of caffeine
  • Body mass of the individual
  • Sensitivity to caffeine
  • Other factors

In this case, Elaine is a 5’ 3” woman who does not normally drink coffee, so she was fairly sensitive to its effects. She was certainly jittery afterwards.

Generally, this effect will last about 1-3 hours. This is why we require our clients to abstain from coffee for at least 4 hours before the RMR test. Of course, using the caffeinated RMR as a baseline for nutrition planning is not advised, as it could lead to inaccurate calorie planning, and consequently, unintended results.

Curious about the speed of your metabolism? Sign up at our storefront in SoCal or at one of our RMR truck events in NorCal - and don’t forget to skip the caffeine that morning!

The BodySpec Team

Tagged: bodyspec, nutrition

Share this post

← Newer Post Older Post →
Twitter Logo

@RobRiches shows us 5 lbs fat vs 5 lbs muscle. Get a @BodySpec scan & make sure you're losing/gaining the right stuff!