I recently started the Keto diet and it has been going well in terms of weight loss. I ran into a snag yesterday. After 11 days on the Keto diet, I decided to go for a 19 mile bike ride. I had done a 10 mile cruiser bike ride earlier in the week with no ill effects, but yesterday I went on a 19 mile ride on my cruiser bike again. The ride took me about an hour and 45 minutes to do. The wind was really high (20+ mph) and I came to find that my back brake was rubbing when I got home, those things usually add a little fatigue to my post ride, but nothing like I experienced yesterday.

Before the ride, I ate a big, zero carb breakfast. During the ride, I felt fine. Immediately after the ride, I felt fine as well. I didn't eat for two hours after the ride and started to feel bonky. So I went and ate a bigger meal that I had in several days. Not really high carbs, but not super low carb either. Continued to feel hangry after the meal and lethargic. Went grocery shopping and had to drag myself through essentially. Got home with little energy and actually took a nap, which I never do.

Ate a small near zero carb dinner and went to bed. Slept 9 hours which is long for me and woke up this morning still feeling slightly fatigued. This coming from a guy that has ridden 4200 miles this year and recently did a 3-day, 160 mile loaded bike tour like it was nothing before starting the Keto diet.

I'm asking this question to a specific group of people just in case anyone here might fall into this category. Are there any longer mileage cyclists on the keto diet on this forum? If so, how did you go from being a sugar-burning cyclist to a fat-burning endurance athlete and keep your energy up?

Do you still carb up before rides? Or do you ride in ketosis? What method have you found that let's you ride the same way you rode before going keto?

It generally takes a couple of weeks for your body to adjust to keto. Also, you may have been pushing it a bit harder than you're used to.

I'm not a "keto purist" since I do LCHF because I'm pre-diabetic, not for losing weight (although I have lost 42 pounds in the last 18 months). I generally do around 30 to 35 carbs a day. I found that I can do a 4 hour ride without problems if I take it really easy. If I'm pushing it, I have to have a boost about 2 hours in. I use the Kirkland dark chocolate nut bars, which have < 10 net carbs. Also, you really have to pay attention to your electrolytes and fluid intake. Keto may cause you to dehydrate a bit, as well as run short on electrolytes, so you have to compensate. I use Hammer's Endurolyte tablets, because they are zero carb.

You say you had a zero carb breakfast and zero carb dinner. I get virtually 100% of my carbs from vegetables. Some people on keto overload on protein, and don't realize satiety has to come from fat in the diet, not protein. Veggies are important as well -- vitamins, minerals, etc.

I can't "carb up" before a ride, because that would cause a spike in my blood glucose. I can have a protein bar in the middle of a hard ride because the extra glucose is used up fairly quickly.

BTW, Chris Froome was on LCHF when he won the Tour, though I'm not sure if it was Keto or not (<20 carbs/day).

There's a lot of BS on the web about Froome's diet. Note the lack of quotes: red flag. If you want to read what Froome himself says about his diet, read this: https://www.redbulletin.com/int/en/s...nutrition-tips
He eats carbs like anyone else, though he puts more emphasis on protein than do most.

There's no proof that eating low carb produces better performance. OTOH there is a lot of evidence that performing low-carb produces better performance. IOW try to eat as little as possible during a ride but drink plenty of water. You can also try to eat as little as possible, of anything, before a ride. Then get plenty of carbs after the ride to restore glycogen. This regimen improves performance in everyone. It also takes weeks or months before one's metabolism changes to increased fat burning, which is one of the main purposes of base training.

There are some LCHF athletes who eat that diet when they are not performing but then eat plenty of carbs during their activities. There are claims saying that works, too, but I don't know if their performance differs from those who eat the usual percentages of macros.

Eat small portions and ride and eat like Froome says he does and you'll have fun on your bike, which is the whole point.

Thanks for the info.

A regular ride for me is 40-60 miles at 15-16 mph. This one was 19 miles at 11 mph.

How many carbs do you take when you "boost?"

How so? Pre-Keto, I could do a 30 mile ride at 15 mph with no food or water. I've never used electrolyte supplements before either.

I take in more fat grams a day than protein grams.

I don't think you can generalize too much from a single ride. Some days you're just "off." But as I wrote, enough people have initial difficulties on keto that it's called the "keto flu." I never had any problems, however.

The "boost" is a single protein bar, with around 10 grams net carbs. I only started doing this when I noticed that 2 to 2 1/2 hrs into a ride, I would start feeling pretty weak. One time I measured my blood glucose at that point, and it was 68. So now if I'm going to ride 2.5 hours or more, I eat the nut bar 2 hours into the ride.

I found from my personal experience that consuming one bottle of water with a single Endurolyte tablet helped keep cramping down to a minimum on my diet. I'm just saying that works for me. I can't vouch for any supplements, since they're totally unregulated in the US, and all sorts of crap is being marketed as "health food."

By the way, as I mentioned, I do keto, or what a purist might term "loose keto" for one reason -- to keep my blood glucose under 125 at all times. And I can prove that it works for me, since I test my blood regularly. I don't claim it's any magical way of eating or something that everyone should do. But if you're a t2 diabetic / pre-diabetic, it's something that's certainly worth trying in order to stay of metformin or similar drugs.

I appreciate you taking the time to reply. I have ridden pretty consistently for the last 3.5 years. Coming up on 15,000 miles during that time. I had it down to a science and didn't have off days right up until that last ride.

I haven't really gotten into the net carbs thing so far. Do you know how many actual carbs it has? And you eat any carbs prior to riding? I feel like there is a ratio I need on ride days, just need to get it figured out.

I understand. Cramping has not been an issue for me. I've only had them temporarily (like 5 minutes during a 65+ mile ride) that included around 4,000 ft of climb. Aside from that, I've never had them while riding the bike. Therefore, I've never used electrolytes while riding.

Thanks for the info.

If this is the first time you've been on keto, though, your body may be responding a bit differently.

According to the nutrition label, there are 14 grams total carbs, 7 grams of fiber, for a net gram total of 7 grams. This is about what is in the dark chocolate KIND bars, and these are much cheaper and taste just as good.

Fiber is a carbohydrate, but you can't digest it, so it doesn't affect your blood sugar or insulin response. It just, um, comes out the other end. You can safely take the total carb content of a food and subtract out the fiber content, for purposes of keto diets and diabetes.

You felt bonky since you had no more sugar on board and your brain isn't used to running on ketones alone.
You should eat after you ride since you burned off most of your glycogen. After a hard ride a protein shake with whey and half and half and/or sugar free almond milk instead of regular milk, maybe half a banana. Or Whole milk yogurt with added whey and nuts, if you do dairy.


I don't carb up or ride keto. I am probably never in ketosis since I eat fruit regularly and pumpkin pie when I can.
I eat lower carb off bike but when riding I'll use a gel and mix some gatorade into my water, since I hit the hills hard and go anaerobic.

Your kidneys get very efficient at excreting salt when you are in nutritional ketosis. Many of the fatigue symptoms are due to not getting enough salt. You might try dinking a cup of bullion before a ride.

Charlie

The whole concept of Keto sorta scares me.... I get it, really I do: train your body to burn fat. But I could never limit my carbs!! Too disciplined for me. I've been eating paleo for over 2 years now and love my fruit too much.

For the folks that can do it, good for you.

I can now answer my own question. After a few months on the keto diet, I have appareantly become fat-adapted and don't need carbs to ride like I once did. I did 83 miles over the weekend in a fairly low carb state and didn't bonk or need sugar to keep pedaling.

There was one several mile section directly into a headwind with no breaks and I thought for sure I'd feel my energy wane or have a bonk during or after, but I did not. My energy level stayed the same through the whole ride. Felt perfectly fine after as well, not a hint of fatigue. I knew something had changed at that point. I don't think I have the explosive energy I had when I was running on sugar, but my endurance seems to be increasing.

It just takes time for your body to adjust to running on ketones/fat versus sugar. I've also dropped 21 lbs. since I started and my blood work looks great according to my doctor.

Grats on the results. Seems like youre adapting well to the training. Making your body more efficient by increasing your fat combustion rate is pretty much what keto/base is all about. Maybe you could push only 30~40% relying purely fat energy, but perhaps you can do 50~60% with low effort.

Really awesome that you gave us the results. Will you work on your upper range power/FTP with a different diet now?

No, I'm doing strictly it for health and weight loss, so I'm going to stick with what's working for now.

I can only give my experience and do not claim it is any kind of "science." I cut carbs severely for about a month last summer. The result was...I didn't lose weight and felt terrible. I was weak on the ride and tired all the time. I went back to my regular carb diet and immediately saw an increase in performance. I also felt a lot better.

I did at first too. That passes if you stick with it. But its not for everyone, for sure.

I have been doing strict keto since middle of February. I have lost weight but like you I don't feel as great as when I ate carbs. I also lost a good 20% of my power and my heartrate is higher. I can't keep up with the guys I usually ride with.
Did an FTP test on Trainer Road last week and my FTP dropped from 257 in January to 201 now with the only difference being on Keto diet.
Glad to know your power came back after eating carbs. I think I am going to start taking in some carbs morning of ride and see if that makes a difference. If not I am going to bail on this diet.

There's a good talk by Dr. Stephen Finney where he goes into the information behind nutritional ketosis and performance, apparently it was a group of collegiate cyclists that they tested on. It's a good listen, and you might get a few good takeaways. Youtube link:

The main takeaway is that they focus on 65% v02max, ie zone 2 cycling. There is a reason for that. The penalty for going anaerobic for extended periods on ketogenic diets is pronounced.