[Evgeny]

I suggest some of Lyle McDonalds articles for a start, for example

http://www.bodyrecomposition.com/fat-loss/how-we-get-fat.htm...

http://www.bodyrecomposition.com/fat-loss/the-fundamentals-o...

http://www.bodyrecomposition.com/fat-loss/the-fundamentals-o...

In case you like his writing, he's the author of a couple of high quality books.

So cutting down on the sugar should tell the body to use more fat as an energy source, yes?

Actually, he answers that almost directly here:

http://www.bodyrecomposition.com/nutrition/nutrient-intake-n...