I notice the dietary advice here is going the "no fat" route. I mean, counting calories isn't wrong, exactly, but all the oils that are very good for you and that help make the Mediterranean diet healthy and stuff . . . have plenty calories in them.
Glycemic index is important. A big question is, how fast does it hit your bloodstream? Processed starches and sugars are amazingly easy to digest, and hit very fast indeed, leading to a spike of so much blood sugar that your body can't use it all. So it stores some away to use later. Where does it store some away? Why, in the body's designated storage area: FAT CELLS. Then, since it's done that, you don't get to actually use all that you've eaten and you quickly get hungry again.
But oils, while they contain a LOT of energy, are harder/slower to digest. Also starches that aren't processed so much, like a bowl of oatmeal. The body processes them gradually, releasing a trickle of blood sugar that your body can use all of. There isn't enough all at once to force storing some away, and the slower trickle lasts longer, so you're not hungry again in half an hour. That's why a bowl of oatmeal "sticks to your ribs".
So avoiding fat, especially if it pushes you to eat empty carbs like, say, rice cakes, is often not the best policy. And before I bought any low fat mayonnaise, I'd take a good squint at the ingredients to see what was in there instead.
