I’ve seen several posts extolling the benefits of weight lifting in a fasted state and decided to do some (casual/Google) research to learn more about it. For some background: I normally break my fast the night before a gym session, because I feel like I can go harder and get in a better workout. My goal is mainly to grow some muscle, I don’t work out to lose fat (I do 48 and 78 hour fasts each week for fat). However, I am interested in finding out if it really is significantly better to break the fast after the gym.
I looked at a bunch of research studies because I don’t normally give a lot of credence to blogs or magazines. However, i did find this one blog post on lmnt’s website that actually does a really good job of summing up what I read elsewhere in the scientific literature. You can read it here:
https://drinklmnt.com/blogs/health/should-you-train-fasted-benefits-downsides-and-when-to-do-it
Interesting points:
light aerobic exercise (like walking) burns more fat in a fasted vs non-fasted state
in contrast, for moderate or high intensity cardio, the amount of fat oxidation is the same whether you are in a fasted or non-fasted state. A study found that the non fasted group actually performed better but had the same level of fat burning as the fasted group.
growth hormone increases 500% after 48 hours of fasting, but levels drop immediately after eating. GH helps to prevent muscle loss, but it does not help muscle growth from exercise. Weight lifting (in the presence of protein) grows muscle regardless of GH levels.
there is one study showing increased anabolic signaling with fasted weight training
This trainer (no idea who he is or his credentials, but he seems to have read most of the same research as I did) argues that it’s good to do low intensity cardio in a fasted state, but high intensity weight training is better done non-fasted. He points out that you will have more energy for better performance, have less risk of muscle breakdown, more immediately available protein for muscle growth, and less risk of overstressing your body. I kind of agree with him. I don’t really see much evidence that fasted weight lifting really has much benefit over non-fasted, and moreover, it has more downsides. Any thoughts?
I lift for over 15 years. In the past i had to eat something, usually rice + chicken breast before workout, otherwise i wouldn’t perform at all. Once i started fasting/ OMAD it’s waas a game changer. I lift for about 7-8 years in fasted state and i perform well. I’ve tried several times to go back to eating 4-5 meals a day, tried pre workout meal, always with poor result.
I feel far better, more energetic while fasted.
I think some considerations should be taken about those posts:
Thx 4 sharing. Bias Confirmed! I do Zone 2 Cardio 16-18 Hours Fasted 5-6 days per week and Heavy Weight Training 2-3 hours after breakfast and just before my final meal 3-4 days per week. I feel good most of the time. Every few weeks I seem to feel overtraining tho and usually take 2-3 days off.
Another interesting study:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4500013/
This one looks at aerobic exercise in the morning fasted (11 hours) vs after breakfast. It’s hard to extrapolate results from a limited short term study like this, but the findings suggest increased fat utilization in the fasted group (as expected), but also higher cortisol levels after exercise in the fasted group. Elevated cortisol could potentially be a negative for muscle growth since it promotes catabolism. The authors suggest that their findings show increased muscle breakdown for energy during fasted exercise. I couldn’t find anything on elevated cortisol and weight lifting, but that’s an interesting thing to consider as well.
This post is awesome; glad someone else was thinking about this. I’ve done 16:8 off and on for years but this week I started doing a OMAD/~24hr fast twice. I’m on a Push/Pull/Legs split Mon/Wed/Fri and the two days I chose this week were Mon and Wed (Sun dinner to Mon dinner, Tue dinner to Wed dinner). USUALLY I suck down some bone broth within an hour of finishing my lifts but these two days I just powered through the whole day until dinner with no real post-workout input other than black coffee, tea, and sparkling waters (and NORMAL water obviously).
I’m in the gym around 5AM on those days so honestly I’m already 11-12hr into my fast anyway; the only difference was no post-workout stuff. My workouts haven’t suffered and I’m actually down 8lb just since last weekend.
Interesting in following this topic as I love lifting but also would love to drop another 10lb or so.
My personal experience is that I’m a bit stronger and have greater endurance when not fasted but my mind-muscle connection is better while fasted (usually around 12h when I work out, I rarely fast longer than 18h or so).
I generally like the feeling of working out fasted more and feel like I can put more effort into recruiting the right muscles and fixing imbalances.
All anecdotal and subjective of course.