Working out in a fasted state on keto qustion

#1

I have a science-y type question. I’ve been on the keto diet for almost 4 weeks and I feel great and have lots of energy. I work out 6 days a week but since I started keto I haven’t worked out in a fasted state. Normally I have my bulletproof coffee in the morning before my workout. But this morning I didn’t have my coffee until after my workout. I hadn’t eaten anything since the evening before, about 11 hours fasted. I was tired and felt sluggish during my workout this morning.

I know that anyone who is not keto, who consumes moderate amounts of carbohydrates, can work out in a fasted state and have ample energy because they have glycogen stores in their muscles that will give them enough energy for a workout. What happens for those of us on the keto diet that doesn’t have those glycogen stores anymore and is using fat as their major fuel source? Is my energy during a workout (in a fasted state of 11 hours) come from my body fat? Is there mobile energy from ketones? I believe I read that ketones are a slower source of energy and aren’t very good at producing enough energy for a high intensity workout. Is that correct? I’m trying to know what to expect during my workouts and want to know if I should have some fats/coffee before my workouts?

(LeeAnn Brooks) #2

It will come from fat stores once you are fat adapted. You could slightly increase your carb intake on workout days, but as you workout 6 days a week, this could really slow down your adaptation time.
If I were you, I would just tuff it out with low energy, take it easier on your workouts and even cut back on them until you become fat adapted. It sucks for a while, but this was my approach and it was better than upping my carbs and it taking me a lot longer to adapt.

#3

Normally, after having my BPC I have tons of energy during my workouts. It was just today when I didn’t have my coffee that I didn’t have any energy.

(Tim W) #4

Maybe your lack of energy was due to not having the caffeine rather than the calories?

I was thinking about your questions and while I’m not a doctor and I don’t know the answers to some of the questions you pose, I would ask you, what is your purpose for working out?

If you want to lose fat, working out fasted seems to work well for some. I personally use IF and fasted workouts to stay in shape and I prefer to work out fasted, I feel more capable.

If your goal/purpose, is to have a better workout, then tailor your processes to support that. If I didn’t sleep well or have a hang-over, I will have some black joe before exercise, it makes a difference for me.

Studies indicate that your muscles will keep a “baseline” level of glycogen stored, even when fat adapted and exercising (The Faster Study…). It would seem that the auto-regulation of those levels keeps a certain amount, probably for “fight or flight” response, when we had to run from something eating us, your muscles had to have the ability. Here is what I think happens… (thought experiment time)

  1. You have fasted for say 24 hours and you use up a majority of your muscles glycogen when moving/workout out etc…
  2. The body won’t allow muscle glycogen to get below a certain threshold, let’s call it 40%…
  3. As you near that 40% level, the body starts making more glycogen via gluconeogenesis and, at the same time, forces you to slow down via increased heart rate, etc… You start to feel week/sluggish etc. and have to reduce effort.
  4. The body restores muscle glycogen using broken down fat stores (this is if you continue to fast).

Who knows? I think it depends on how long you are keto, how much experience you have in this realm etc. I have seen/heard suggestions that simple carbs (sugar etc) might be “better” for explosive work (box jumps, plyo stuff) but each person’s results will vary.

I could keep going on this for another couple of paragraphs but I don’t know if it would have any value so I’ll stop here for now. I will list what I listen to/read (other than two keto dudes…) if you want to learn more on this topic.

  • Primal endurance podcast
  • Endurance planet podcast
  • The keto athelete
  • Anything by Peter Attia (lots of DEEP, technical stuff)
  • Phinney and Voleks stuff
(Katie) #5

This is what I was going to write as well. Definitely something to experiment with. I just consume black coffee before workouts and I am fine, but of course everyone/body is different.

#6

If you’re eating, even if it’s a HFLC protocol, your muscles are probably not depleted of glycogen. For most people it takes a couple of days of fasting. Time restricted eating (ie. 6 hour eating window and 18 fasting window) usually isn’t sufficient. It takes a while to get in a deep ketotic state. Even then, the liver is able to supply the necessary glucose and fatty acids the body demands. When I am in ketosis (BG in 60s and BK 3-5) and do a very demanding workout, my glucose and ketones can drop for several hours.