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Due to an injury followed by a stomach virus, I drank a lot (coke, iced tea, and water) but hardly ate anything for 5 days. Now, my weight has dropped by 3 lbs.

I feel like I lost muscle mass. However, my doctor told me that while not eating I would have used up fat, not muscle.

If I stop eating for a week, will I loose muscles or just fat?

Clarification: This was not on purpose, I simply couldn't eat.

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Your first question is a duplicate of this:… I left the second question in tact. – michael Jul 30 '12 at 16:49
What did you drink? If it was caloric at all (Such a fruit juice, pedialyte, etc), then that will make a difference in how the body reacts. There is a huge difference between 5 days of no calories vs. 5 days of lower calories. – JohnP Jul 30 '12 at 17:54
@JohnP: Caffeine free coke, iced tea (with sugar), and water – S. Robert James Jul 30 '12 at 23:48

I'll make an assumption that what you're really worried about is how much will your strength be affected in your next workout. That is, how much should you deload when you restart your lifting program?

I had food poisoning that affected my diet for about a week. When I returned to the gym, my squat had dropped from 230 to 215, shoulder press from 95 down to 85.

But, whether or not that is due to actual muscle loss, I don't know. After a week of sickness, you're probably poorly hydrated, you'll have depleted glycogen stores, creatine levels will be low, you'll have missed your super-compensation phase and may have begun deconditioning. You'll definitely feel less strong.

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Well, I pretty much expect to have to deload the first time back. My question is: Is that one time only, or am I really pushing back a few months? Keep in mind that I lost 3 lbs while out. – S. Robert James Jul 30 '12 at 23:50
I had to deload and re-build strength over several workouts, but it was a few weeks worth of rebuilding to get back to my previous strength, not a few months. – user3085 Jul 31 '12 at 0:14

Your doctor is closer to being right (but probably not 100%).

The body starts eating muscle when you're out of glycogen. If you're drinking sugary beverages (i.e., not diet) that will delay the onset of chowing down on muscles, at least to some extent.

You'll become marginally de-conditioned after five days, but not radically; most of the issues will be related to not having sufficient fuel stores to bust out a pre-weakness workout.

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Your doctor is correct, see this website:

After about day 5, the energy taken from fat stores is the greatest. If you continue to fast longer than 5 days, the proportion of muscle burnt begins to increase.

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There has been conflict results that have been reported before whether short term fasting has an effect on protein loss. However a number of studies now show that protein breakdown increases during short term fasting so it's very possible that as you are feeling that you actually lost some protein and not fat only. You can follow this article for more evidence.

There is also another review which has 3 other studies which also support the aspect of increased protein breakdown during short term fasting.

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First thing your body use is carbohydrate (your sugar drinks are high in carbohydrate), then fats, lastly protein. Muscle is protein. And if you're not moving much, your carbohydrate are converted to fats. So you probably just lose some fats.

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