I'm fasting (water only) for an undetermined amount of time (7-14 days) for personal reasons, but I want to continue my workouts so I don't fall out of the habit. I'm afraid if I let myself skip them I won't restart right away, leading to months of inactivity - it's happened before!

Typically, I have 2-3 cardio workouts a week (30min to 1hr of running/cycling) and 2 weight lifting workouts (3x5 barbell squats, rows, et cetera)

What can I do to ensure safe workouts while I fast? I'm considering modifying/cheating my fast to include milk on workout days, would this help with the weight lifting? Or is this crazy and I should take a break from the exercise, too?

  • 1
    I have no expertise on this topic, but I'd at least dramatically reduce your weekly training volume during the fast. Half the training with reduced weights would be fine--you'll almost certainly loss strength and conditioning, but I'd be concerned with "bonking" if you don't. Commented Aug 22, 2012 at 14:21
  • 1
    What are your training goals? It's possible that your training time will be useless if you're not feeding yourself, and it may be better to just not do them.
    – user3085
    Commented Aug 22, 2012 at 15:46
  • My goal is to not fall out of the habit during a 1-2 week fast.
    – mebassett
    Commented Aug 22, 2012 at 16:04
  • Then there's nothing wrong with workouts while fasting if your only goal is to be present for them, and have no volume or intensity goals.
    – user3085
    Commented Aug 22, 2012 at 18:05
  • Cool story. I'll cut the weight, reduce the reps, and keep the runs short and easy. Thanks. If you want to make this an answer I'll accept it.
    – mebassett
    Commented Aug 23, 2012 at 9:22

1 Answer 1


I wouldn't do any heavy workouts while fasting. One time I had neglected to eat (not due to fasting, but due to being distracted) for a while before my workout and I miscalculated the weights I was lifting - increasing my previous max by 40lbs instead of just 10lbs. That was not good for my form.

For marathons I wouldn't really go more than 45 minutes between eating carbohydrate packs, unless I'd loaded up on quark in the morning.

If you were planning on doing a 40 day fast, I might suggest throwing in a couple weight lifting runs spaced 1-2 weeks apart, but even that probably isn't without risks. If you're only fasting for several days, up to a week, I'd just take a break from the workouts as well.

  • No heavy workouts for sure. But what how should I change the workout for a fast somewhere in-between a week and 40 days?
    – mebassett
    Commented Aug 23, 2012 at 9:24
  • @mebassett Do you normally do warmup sets?
    – Robin Ashe
    Commented Aug 23, 2012 at 11:22
  • @robin_Ashe indeed. 5 reps, 3 reps, 1 rep starting at roughly 50% and ending at roughly 90% of my workout weight.
    – mebassett
    Commented Aug 23, 2012 at 11:28
  • @mebassett if I were doing that I think I'd stick to the first and second warmup sets, and just leave it at that. depending on the exercises you do, I might abbreviate the selection as well, down to 3 or 4.
    – Robin Ashe
    Commented Aug 23, 2012 at 12:03

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