How can atrophy occur with less protein if maintance calories are intaked?

[sfetaz]

Lets say someone is 200 lbs at 10% body fat. That would put them at 180 lbs lean body mass. They do not do any exercise at this time.

Now lets assume they ate a good diet with 40% protein, 40% carbs and 20% fat and that their maintance calories for this person is 2600 (200x13)

Now this person changes their ratios around to say 60% carbs, 20 % protein, 20 % fat. but still ate 2600 calories. Not that there is a good reason for this, just trying to figure something out.

Since this person is still getting protein (about 105 grams a day), and is eating the amount of calories they burn, how would the body still have atrophy? The body has no need to burn muscle for enegry since there is no calorie deficit, and is still getting protein in the day. I understand the logic of the body recreating itself all the time and needing nutreints to do this, but the body needs less when there is no stress activities like exercise going on, so how can this person still lose muscle mass? At the time of the bodyfat measure it is assumed that the body has not gone through exercise of any form.

[BigBenn]

may answer to that is that there is in fact a deficit and a surplus of cals at different parts of the day. Through the night or other time without food you go catabolic and lose muscle. Then when you go back to anabolic by eating you gain some muscle back but also some adipose tissue. It is like taking 2 steps back then 1 forward.