Rod Munch wrote:
Negative energy balance means you are eating less calories than you are expending. That's it. It is not more complicated than that. There are no "special cases." Really fat people definitely do not gain muscle when they lose fat. They definitely lose muscle.
The 10's of thousands of fat calories you have stored don't matter when you are eating less than you are expending- you are in NEGATIVE BALANCE, so you will use fat AND protein for bodily functions. Over a time period of negative balance, you will have net muscle protein loss. You CANNOT synthesize it. How can you?
I really can't believe how many people there are who believe the "gain muscle while lose fat" fallacy to be true.
If you all think I'm so uninformed, why haven't any of you explained how the opposite can be true?
First, there's a basic logical error here that is very common in students learning about sources and sinks. Just because my net energy balance is negative doesn't mean I am consuming zero calories worth of protein or carbs. And if I have protein coming in then it is *possible* that my body can use it to synthesize new muscle. So the "You CANNOT synthesize it" argument is wrong.
It sounds like you think this is very straight-forward thing and that "having a negative energy balance" is some well-defined thing that automatically and unequivocally leads to some end result.
Perhaps you can be convinced that it's not so simple.
Think about the time frame over which your calorie input is less than your calorie expenditure. If the timeframe is "your life" then clearly every living thing is in a positive energy balance. No living thing has ever spent more calories than it has consumed if you start measuring from the point of conception. We're all in positive energy balance until we die. Now I realize that's not the time scale you're talking about. But indulge me and think about the other end of the spectrum.
For the last 5 minutes I've been eating breakfast (while sitting). If I measure during that time period I clearly have positive energy balance: the number of calories I took in was much larger than those spent. However, during the proceeding hour I was in the middle of an easy 10 miles. Clearly if you look at just that time period I was in a negative energy balance (I consumed no food and burned 1000-ish calories). Likewise, from now (having just finished my cereal) until lunch my energy balance will be negative (no calories consumed, some spent for maintaining stasis, walking to work, typing on a computer).
The point is that the notion of 'energy balance' is meaningless unless you specify a time interval. Measuring over our lifetime it's always positive, and over periods of minutes or hours it's usually negative (unless we're actually eating). It's a logical construct, not some piece of biological reality.
Now I realize that the negative energy balance you're thinking about is likely a period of days/weeks over which the average is negative. And I'd certainly agree that whether the daily/weekly average is positive or negative triggers all sorts of hormonal responses in the body. And those responses will definitely change the mix of fuel burned in the body. But what fuel is burned and what proteins are synthesized in a particular tissue in a particular location in your body is a result of the local environment *in that instant*. Certainly global flows of hormones (which are affected on average by longer terms energy balance) play a role. But it is naive to think that there's some global switch throw when you cross some calorie balance that suddenly halts the ability of every cell in the body to synthesize new muscle and/or burn fat.
The reality is that you are continuously burning fat, protein and glycogen somewhere in your body all the time. There is *always* synthesis of new muscle tissue going on (and breakdown of old tissue). There is *always* burning of stored fat going on (and accumulation of new fatty tissue). Each cell is making it's own 'choice' based how external stimuli have induced local enzymatic activity. The cells in my calf, stimulated from my run may be building muscle--those in my pinky are not. The hormone shifts stimulated by day and week scale calorie deficits will certainly swing the mix one way or another. But to say you can't build muscle tissue if you're losing fat is (as others have said) simply wrong.
Or if you want the simple math:
If I need 1000 calories day to maintain stasis and I need 200 calories worth of protein a day to build new muscle in response to intensive lifting (all I'm doing is sleeping and right bicep curls), and I consume 500 calories worth of protein and 400 of carbs every day and I have 20,000 calories stored as fat is it possible for me (over the period of a week) to gain muscle mass. Purely from an energy balance point of view (which is what you're arguing) I could spend 600 calories from my stored fat and 400 from carbs to maintain stasis and still have more protein than I needed to put on the muscle even though I'm in a negative energy balance (and am losing weight due to fat metabolism).
Now would a body actually respond in this way? Of course not. But the reason is *not* because the simple energy balance math makes it impossible. Because clearly it doesn't.
Now you could argue that the specifics of the hormonal changes brought about by medium term energy deficits cause body-wise averages of tissue gain-tissue loss (muscle and fat) to give a net result that total body muscle mass never increases at the same time that total body fat mass decreases. But that's a pretty complicated argument. And while straight-forward to assert as fact I'd very surprised if anyone knows the details of all the systems involved sufficiently to make a compelling definitive argument.
It ain't simple and you haven't proven it. Not even close.