Sugar - The Bitter Truth (Dr Lustig)

When we eat, there's a hormone called leptin which signals to the brain to stop eating once we had enough calories or energy intake. When we eat a high carbohydrate meal, leptin is not doing it's job. That's why we are still hungry after a big chocolate cake, but we are not hungry even after a small high fat diet meal (if it is not consumed together with carbohydrates).

In these videos you can find details about the metabolic effects of sugar.

And here, you can have the sugar metabolism explained in detail: