How do you know if you have a slow or fast metabolism? There are a lot of advice about what to eat and what not to eat in order to stay at a healthy weight, but each person has a different metabolism, right? So how come we all are supposed to eat the same way in order to lose weight? Has anybody heard of the "metabolic type diet"?

Also, I am a bit at lost with all the fuss around carbs and grains: rice and pasta are supposed to play a role in gaining or losing weight, but half of the planet has a diet solely based on white rice and they are far from being overweight (I am thinking Southeast Asia in particular). Are genetics a big part of the equation ?