>>17
I'm not totally versed on what the deal with fat is, but for sugar it's not so much the amount you get, but rather the rate at which it's metabolized by your body. Anything with refined sugar in it (pretty much all sweets) and white bread products raise your glycemic load by a substantial amount very quickly, putting strain on your pancrease as it works hard to release insulin so that your cells can metabolize the sugar. Eating whole grain foods like whole wheat bread or brown rice lowers the rate at which the sugar in those foods is introduced into the blood, which lowers the glycemic load (even though the total amount of sugar being consumed is roughly the same) and therefore lowers the strain on your pancreas.

That being said, sugar and fat are essential parts of your diet, you just need to make sure you're getting the right kinds in the right way (eating a pint of Ben & Jerry's is not the right way).