My heart rate is higher on ketogenic diet

Question: why is my heart rate higher on keto diet.

My resting heart rate has always been in the high 40s to low 50s range, even when I was very fit and athletic. Since starting a ketogenic diet, it’s now 56-58 all the time. Is this normal?

It feels like my heart is working harder/beating faster just because there’s less oxygen around to go to muscles with. I’m not sure why or if that makes sense, but that what it seems like. Thanks for any insight you have!

Answer: The one study I can find which compares cardiac output between keto adapted individuals vs those using glucose as their primary fuel source show a significant increase in cardiac output from 10 to 12 weeks [1].

In this study, I’ve highlighted where differences in the “keto group” were significantly different from the “glucose group”. In response to a ketogenic diet,

myocardial blood flow is slightly higher (2.9%; p < 0.01), while stroke volume and resting heart rate are slightly lower (5% and 6%, respectively; both p < 0.05).

Cardiac efficiency is also improved by ~6%, resulting in a reduced oxygen consumption per beat of the heart (i.e., lowered base deficit). Data adapted from reference [1] 

It appears that there’s no difference between men or women when it comes to increased heart rate. Here’s why I think this is happening:

The increased cardiac output could be due to the induction of both mitochondrial biogenesis and angiogenesis which occur in response to chronic ketosis [2].

The heart DOES use ketone bodies for energy, just like every other cell in the body does. This would increase mitochondrial density or both sub-sarcolemmal and intermyofibrillar mitochondria shown here (Figure 3) .

These are all indications that your heart muscle has grown more efficient through adaptation to a low carbohydrate diet.

I’ve been on a low carb high fat diet for a month now and my resting heart rate has gone from 45 beats per minute up to over 80 beats per minute at rest.

My resting heart rate has gone from 45 beats per minute up to over 80 beats per minute at rest.

I’ve been on a low carb high fat diet for a month now and my resting heart rate has gone from 45 beats per minute up to over 80 beats per minute at rest.     

It usually fluctuates between 60-85 bpm when I am laying down or sitting completely still, but while I’m walking it will shoot up into the 90s and 100s!   Is this normal because during the first few weeks I was only running about 50-60 bmp. What would cause this?

Answer: When someone starts a ketogenic diet, there’s an adaptation period where the learns how to efficiently burn ketones. This is why there’s a ramp up in heart rate as it learns to burn ketones vs glucose.

Eventually the body will switch from primarily burning glucose to primarily burning fat and this period of time is called “keto adaptation”. The cardiovascular system gets a workout during this time, which also explains why you’re out of breath more frequently when exercising.

During keto-adaptation, the nutritional ketosis itself may cause a natural increase in resting energy expenditure as well as mild hyperketonemia. Usually within four weeks or so, most people finally adapt and feel great on this diet!

Here’s why I think your heart rate is elevated:

  1) Increased cardiac output which comes with increasing mitochondrial density

2) Nutritional Ketosis is associated with mild hyperketonemia. Hyperketonemia means higher than normal levels of ketone bodies in the blood stream.

The increase in plasma free fatty acids (FFA), beta-hydroxybutyrate (BHB), and acetoacetate during this period all contribute to the rise in resting energy expenditure

3) Since you are using more fat for fuel vs carbohydrate, Your body uses more calories at rest to maintain itself, hence why you are out of breath more frequently when exercising.

Most people adapt within 4 weeks or so, if not sooner. You can also look into MCT oil or ketone supplements to see if it helps speed up the adaptation phase.