IamEvan saidIt's a myth perpetuated by one study showing that the body can only digest up to 30 grams of protein at a time - hence the need for several small meals. Several other studies have disproven this myth and there is no need to eat 6 small meals a day or anything. You can if you want, but it doesn't boost your metabolism or anything like that.
Eating frequently causes your blood sugar levels to be much more stable, but, on average higher, but not spiking as high, and you don't go too low, or too high. Higher blood sugar levels allow you to perform more work, longer, stay hydrated and have better cognitive function. I'm not talking over the top blood sugar (which causes insulin tolerance and type 2 diabetes).
Research how insulin works. Insulin is the shuttle hormone. The cellular pump.
Losing weight is about eating fewer calories than you consume. If you drive yourself into ketosis, and your blood sugar goes low, you go catabolic, and end up with low blood sugar. Your metabolism slows in what's called the famine syndrome (from years of living in caves) and you catabolize muscle. carb deplete, first from your muscle, and then from your liver, and then you convert protein as opposed to fat (the famine protection) back to blood sugar (glucose). Nice, stable, blood sugar levels, moderate appetite, keep you anabolic, and preserve your cognitive function.
Now, that being said, if you're very lean....and active, and getting plenty of calories, you get much better nutrition partitioning.
Fasting is a bad idea, for a lot of reasons, some mentioned above. Eating smaller meals, and less carbs, frequently to lean out, preserves your metabolism. To gain, you add in more carbs, and a bit of fat, and maybe back the protein down just a bit.
If you don't eat carbs, water doesn't have anything to bind too in your muscles, and you'll look dry and flat, but, feel "tighter."
All this depends upon your activity level and diet composition, as well as your body composition and your insulin sensitivity.
I don't get most of my own info from some other muscle head (some are clueless). I read my ass off on sites that bring quantifiable science to the table, and, I think things through, every which way.