Errr ... I disagree ... I hate blanket statements like that ...

Some products are crap, some are very good.

Bodyburn and some of the EAS supplements, for example, are very effective.

Also, your maths is wrong. There are different types of fat - saturated and unsaturated - which have different effects on your body. Also, some people gain a lot of weight from carbs. It works a lot better for many of us to try not to eat carbs after 4pm because then we don't have time to burn it off.

Food is a lot more complicated than you suggest ...