There are issues with carbs (they increase glucose+insulin). There are issues with protein (they stimulate IGF1/mTOR signalling).
With fats, the non-(omega 3) polyunsaturated ones can promote inflammation. Also they're prone to lipid peroxidation. Omega 3's can be helpful, but it's hard to get omega 3's as a primary calorie source unless you're a heavy fish eater or eat huge amounts of fish oil (neither of which I'm willing to do).
As for saturated fats, there's a very heated debate over them. But while the debate rages on, I'm inclined to believe that MUFAs are healthier.
They seem to be the perfect source of calories ever. They don't increase glucose or insulin. I don't see how they increae mTOR signalling (although it's possible that they might). If they're burned for energy, they'll be burned through beta-oxidation, which produces fewer free radicals than catabolism of glycotic endproducts (they also don't go through glycolysis, which is another major source of cell-damaging aldehydes). Also, MUFAs are a big part of the Mediterranean Diet.
In fact, sometimes I wonder.. is it possible to be metabolically in a calorie restricted state even when one eats plenty of MUFAs? I suppose more MUFAs = more fatty acid oxidation = higher ATP/ADP ratio (and a higher ATP/AMP ratio, which would reduce AMPK levels). And AMPK signalling is associated with some of the benefits of calorie restriction (though they probably aren't the primary benefit of it).
Edited by InquilineKea, 29 March 2014 - 04:55 AM.
