Trying keto and HR is through the roof with minimal efforts and during workouts

I know most folks here advocate carbs for training and I understand the benefits. My wife and I both have a good amount a weight to lose, and she’s committed to try keto so I want to eat that way with her for a while.

I’ve tried keto in the past and have had some luck dropping weight – in 2018 I lost 61 lbs but since gained 30 back. I’m 250 lbs (113 kg) @ 6’5" (195 cm) and want to get to 190 lbs (86 kg) eventually. I picked up cycling in spring 2019 and have done about 5000 miles since and TR of course.

Even with all that time on a bike, I can’t seem to drop any weight so I decided to try keto again along with my wife. She’s not particularly active and thinks keto is the only thing that will work for her. 5 days in, I generally feel like I have plenty of energy, I try to get my electrolytes, and have been aiming for a 600-1000 cal deficit while not feeling hungry. I’m eating generally healthy low carb foods (avocado, salmon, nuts) rather than just eating a pound of bacon every day!

My heart rate has been through the roof and I didn’t have this problem pre-keto. As an example, I did Acho (3x12 min @ 80%) 5 days ago. The intervals were 212W and my HR was consistently averaging 133 BPM. This was my first day on keto so still plenty of glycogen in the muscles. I did Acho again 2 days ago and the last interval I averaged 148 BPM @ 212W. I couldn’t finish Gibbs (2 hr endurance) yesterday. I hit 153 BPM in a 13 minute interval at 188W. for reference my max HR is 172 based on my last few ramp tests. While I generally seem to feel alert and have plenty of energy, my HR seems particularly elevated even with simple things like climbing a few flights of stairs.

Do you think this is something I should be concerned about? Should I turn down the workouts for a few weeks to keep the HR in check while I get used to keto? Any thoughts or experiences are welcome. Thank you!!

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Your HR is elevated because not eating enough carbohydrates eff’s up your hormones, resulting in dumping of water and electrolytes, shrinking your plasma volume. This compromises your heart’s ability to pump blood, reducing your exercise capacity and putting you at greater risk of heat injury.

The solution is simple: forget the keto nonsense, and eat more carbohydrates.


Nonsense or not, my wife is doing keto and I’m trying to be supportive. Low carb is the only way she’s had success dropping weight.

Your point about blood volume is well taken and makes sense.

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I have been having gradual weight loss for over a year. You might try a lower carb program but not on the bike. I fully fuel my WO with carbs but then maintain healthy choices on all other meals. You can then be supportive of your wife but also fully fuel your WO. I typically (depending on the TR WO) eat a gel 20 min prior to the WO and then fully fuel within the time frame given by TR. I would also go for a 300-500 calorie deficit. Overall, doing this I have not had WO issues nor overwhelming cravings. FWIW.


I think your approach makes sense…thanks for the input!!

We can still eat healthy stuff together and ditch the junk food.


HR through the roof is common among those i know who have tried keto. As a cyclist, you have no business being keto if you value not feeling and performing like crap.

Eat what she eats, add some carbs. Sure keto has some benefits, but is no more effective for weight loss. If you’ve had no success dropping weight with carbs, you’re doing it wrong.

I tried Keto with my wife a few years back and had a similar experience. Find a good electrolyte drink, we used Ultima Replenisher, keto friendly and no sugars. This helped a lot just staying properly hydrated. Bring the intensity down for a few weeks and do mainly easy endurance work. Once you body starts to adapt you will notice your heart rate comes back into check, about 3 weeks for me. The endurance rides and workouts are great on keto, no issues after getting past the initial struggle. However, and this is why I ultimately gave it up, the high intensity work and intervals were always a struggle. If you continue it long term I would suggest getting down to the weight that you want and then on your hard days fuel with some carbs.


If you go low carb or no carb you should clearly also go low intensity/high volume, so rather Traditional Base and long long long Z2 rides.
That is what I am doing after being not well off with SS/high intensity workouts. My HR, my overall body response was all over the place and left me half dead for a day or two. So maybe go really lower side of Z2 for some weeks and gradually increase the effort level so the body cam adopt to produce enough energy.


I don’t have a lot of experience with keto so I’ll defer to the answers above, but I’d also add that it’s probably worth retesting your FTP to more accurately represent the dietary conditions under which you’ll be training. A reduced capacity for high-intensity work on keto could well translate to a lower FTP (particularly as derived from the ramp test) so you might need to work with a lower number in order to train in the right zones.

Also probably worth mentioning that 600-1000 calories is a pretty aggressive deficit even without trying to maximize performance during workouts, and will almost certainly affect your effort levels regardless of dietary composition. It does sound like you’ve got other priorities regarding your choice to go keto (which is fine), but if your performance on the bike is any kind of priority I’d recommend running a smaller deficit.

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Seems like that’s the consensus! :star_struck:

You raise a good point about retesting and I fully expected by FTP to be in the tank. Intervals at 80% a week ago were easier than 70% on keto thus far. Regarding the deficit, I had luck with an aggressive deficit on keto before I took up cycling. The higher fat component was quite satiating so it was easy to get by on less. It seems like that’s less manageable why trying to maintain a modicum to fitness now!

I understand keto isn’t optimal for performance minded folks but my priorities are first to be supportive of my wife who’s struggled with her weight all her life, second to lose weight so we’re both healthy, and third to maintain some bike fitness.

I appreciate the input!!

Another thing to consider, is when you work out you will need more calories. Except those calories can’t be made up after the workout without compromising the workout.

With carbs, you can get away with filling just prior to and during the workout. With keto and running a deficit, you need to have that extra fuel early enough to actually be available during the workout. For keto food, that’s probably like 2+ hours prior.

Heck, even with using carbs, when riding hard and long it’s not fully possible to replace all the calories and I find eating a bigger meal 2-3 hours prior is really essential to my performance.

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I would also suggest that you make sure that you also include a recovery drink. I forgot to add that.

eat a sensible balanced whole food diet and the weight will fall off.

this keto trend is god awful.


Fuel your workouts with carbs before during and right after. Then eat Keto, paleo, whatever the rest of the dAy. There’s lots of books out there for low carbohydrate diets( for athletes) that can guide you in the right direction.

I spent a few months one summer riding 100% zero carb/keto and/or fasted rides. Had no issues with HR/BP spikes, plummets, wonky readings et al. And there were more than a few 5-6hr rides in the collection.

My heart is very healthy. What actually did mess up my heart was a heavy load of sweet spot training.

I’ve since given up both and am faster than ever.


6 years ago I started a Paleo form of eating. It took me about 2 weeks to adapt to the lower carb style eating. When it happened, it was like a switch went off. I lost my constant craving for food and my workouts became much easier. Give it time and don’t be afraid of carbs, especially post exercise. Just choose wisely. I have a relatively low heart rate now.


More bro science…take this with lots of salt. Literally!!!
Done Keto and experienced the same thing early on. On Keto you lose a lot of fluid and electrolytes. Low plasma volume can cause a high HR…I started adding more salt to my food. More than most people feel comfortable. After a few weeks my HR was back to normal and i felt great.


Did you stick with the keto? I did some metabolic testing (before keto) and found I burned very little fat while riding even in z1/z2. I’d hoped trying keto would ramp that up and help drop some weight. I don’t race but am looking forward to some longer rides this summer so I figured being a better fat burner couldn’t hurt.

How’s paleo working out for you? When I had luck with keto before I started cycling, I found one of the best parts was not being hungry all the time. It was easier for me to maintain a deficit since the fat/protein (for me anyway) really curbed my cravings to snack


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