Max Heart Rate


Has anyone noticed a change in their maximum heart rate since starting keto?

Mine is down 10 beats per minute, which translates to a loss of performance.

(aircraftwelder) #2

Somewhere here there is science talking a 28% hydraulic increase in the efficiency of the heart on keto. So 27 % more blood flow per stroke. So lower rate same performance.


Not really sure where this comes from since I’ve heard the opposite that lower heart rate is associated with longevity and increased efficiency. Dr. Doug McGuff has self-reported resting HR in the 50’s and he’s definitely not impaired his performance.

I have activity trackers that show higher rates are associated with stress and lack of sleep and definitely feel worse at those times and spontaneously seem to exercise more when my HR from the last day or so was lower.

Yep, I’ve heard the same thing about increased stroke volume resulting in increased cardiac efficiency.


@aircraftwelder, Yes, Richard mentions that in a podcast (and in an errata), and that may have something do with my decreased heart rate at exertion.

My resting heart rate has not changed on keto. It is 50 at my desk and low 40’s lying down. I have been wearing a monitor for the last two years and check this daily at various activity levels.

There are various distances that I run and each distance has a speed at which I am just pushing myself but can maintain the speed for the distance. My average heart rate for each of these workouts is about 10 beats less than it was pre-keto (aka February 2017). My max heart rate (like from a VO2 max test) is also down about 10-12 beats. All my run times are slower than they were pre-keto.

I am hoping that as I continue to get more fat adapted then the heart rate (and speed) will return.

I may also, once I am done playing with weight loss, increase my carbs to help with glycogen. This is because I am guessing that my glycogen stores are simply too low on run days to be able to provide the energy that fat can not provide.


Any blood pressure change?


No, pretty consistent at 90 over 60 or just above sometimes.


A heart in distress needs to pump faster or harder.

I’m not convinced you are experiencing lower performance.

An athlete versus a non-athlete on treadmills will differ. The non-athlete’s heart pumps faster, harder and reaches maximum much quicker…while the athlete’s heart has an easy smooth operation not in distress.

(aircraftwelder) #8

Interesting, I think it takes a very long time to be able to access fat for energy at the same rate we once got from carbs.


Yes, I think that and I hope that. If that is the solution, then it is measured in years I’ll bet with respect to the max heart rate.

I was tested at one month in ketosis and was able to burn 1.28g of fat per minute which was at about 82% of VO2 max (and about half carbs still). I lack the efficiency that I once had, but my fat-burning ability is higher than any of the non-keto athletes tested by Volek and others that are references in his book. I am in limbo, not great with fat or carbs for max heart rate. I will focus on training that.

(aircraftwelder) #10



I conducted an experiment on myself and ate high carbs (like 500g per day) for a week near the end of April. My heart rate came back (increased a good 10 beats per minute at various high-exertion levels) but my performance did not come all that way back to the same level that I had at those heart rates before keto. I felt like I was in between being a fat burner and being a glucose burner. I also gained about 10 pounds.

I think that my performance on keto will get back to the pre-keto level. I am glad to have gotten an answer to my heart-rate question. Also, I can stop wondering what it will be like to “fall off the wagon”. BTW, it did not feel great.

I am now committed to strict keto. I restarted May 1, and did not skimp on the calories to ease into my chosen WOE. I have lost the 10 pounds in a few days by eating 30g carbs, 125g protein and about 370g fat (for about 4000 calories per day).

I gained over a pound a day eating less calories and more carbs then lost over a pound a day eating more calories and less carbs.

Even a carb-eater can run in zone 2 and burn fat. Most healthy people can probably do that for a half marathon. The closer you get to max heart rate, the more carbs humans burn relative to fat. I think that it takes a lot of time (likely several months) to push your fat burning ability to the point that you can run, say a half marathon, at the same heart rate on keto as you did on carbs. Being “in ketosis” or being “fat adapted” for daily living is not the same as being fat adapted to running your fastest pre-keto race in heart rate zone 4. I will need to be patient.

My macro plan is an average of 20 carbs, 90 protein, and 270 fat daily (although I have much lower for three days and much higher for four days). I expect to lose weight on this plan and to simply remove the “much lower” days to 2, then 1 then 0 per week once I am at my perceived ideal weight. Then all I can do is adjust fat to maintain weight and stick with it and hope to see the performance gains.


This is interesting because I have found the exact opposite. I have been strictly Keto for 3 months now. I ride a bike with a power meter and have found that my power has reduced by about 20% and my resting heart rate has increased by at least 10 bpm. My heart rate goes up much higher with much less effort.
Not sure how much longer I am going to give this. Idea of wanting to lose weight inorder to ride faster has backfired. I am riding slower even though I have lost weight becaues I just don’t have the power output I used to have.
The research that I have done has suggested that this is due to lower stroke volume possibly caused by low sodium. I have increased my sodium to see if this helps any.


Yes, most my reading has indicated that your situation @Sasquatch16 is more normal. I have not found anyone who has written that their heart rates dropped at exertion; but I am pretty sure that many have this as they indicate decreased performance on keto.

Let’s assume that a person is not feeding their body any carbs. I know that liver makes glucose, but let’s ignore that for now.

Let’s assume that in the absence of carbs, fat is burned. I know that there are also ketones, bur the VO2 tests and the Volek study compare only fat versus glucose.

If a person can burn only 1g of fat per minute (which was considered the max possible pre-Volek) AND they are not eating any carbs then they can not burn much more that 9 calories per minute. Therefore they can not go faster running or cycling than what they can go on 9 calories per minute.

For me, I think that my heart is the limiter that simply won’t beat any faster than the beats per minute to perform at the rate for a given exercise at the rate of 9 calories per minute. I need to increase my fat-burning capacity in order to increase my heart rate. BTW, my resting heart rate has not ever changed throughout all of this.


I am also going to try eating some oatmeal and Karo syrup before next group ride. I find that I am usually in zone 4 or 5 most of the time trying to keep up. Hopfully the carbs will help. They will surely be burned up by the time I am done riding. It will certainly increase my blood sugar but do not know if it will add to muscle glycogen in that short of time. I need to do something to get my power back.

(ianrobo) #16

And Peter Defty went on the Primal endurance podcast to explain that for Keto actually you increase your HR on a per effort basis which makes lowering a max an interesting one. I would ask is as much effort being put in when you do a Max HR test ?

(Todd Allen) #17

Theoretically one gets more energy (~30% I think) from burning fat or ketones than glucose with a given volume of oxygen. Thus it would seem reasonable that at a given level of energy output ones heart rate might decrease if a greater percentage of total energy was coming from fat. My guess would be that you are bumping into a rate limitation issue of how fast you can process/burn fat which isn’t yet matching your previous rate of burning glucose that isn’t constrained by oxygen but by some other factor. Dr. Peter Attia who has engaged in endurance swimming and cycling in both high carb and keto states has a blog on which he has mentioned having good results using a resistant starch product SuperStarch while otherwise low carb.

(Todd Allen) #18

Here’s Peter’s blog article discussing exercise performance with respect to ketosis and other factors like SuperStarch.


Yeah - max effort was ALL I could do - and I kinda wanted to kill the two administrators. Also, I have dozens and dozens of runs recorded with average heart rates all down 10-15 beats per min.

(ianrobo) #20

interesting stuff, not done an all out effort recently checked my previous max was 192, highest recored over 3 months has been 187


I wish that I had a max heart rate of 192 or 187. I hit 250 a few times in my 20s, but really only 200 a few times since then and in the last few years it has been only low 180s and sadly on keto only 170. I know that if I have carbs, my heart rate will be higher. I am on a mission to be strict keto with a 180 max.

The admins of my VO2 max test said that I was unique in that my fat burning was the highest they have ever tested (1.28g/min around 82% of max) but that my max heart rate was low.

Perhaps my liver does not make much glucose or I should otherwise eat more carbs. I think that somewhere around 50g might be fine and give that extra bit of glycogen that I may need. I count my carbs conservatively with adding one to most things that say they have no carbs and keep it to 20. I fear that if I eat more carbs then I will crave more carbs, so I don’t want to increase it until I am deeper into this WOE.