Should one eat breakfast,lunch and dinner plus a snack too speed up metabolism and too lose weight?

Yes, as long as the snacks are low in calories and fat, like fresh vegetables and fruit.  Eating even more, smaller, meals is good for losing weight, up to six meals a day, but you have to be careful about the sugar and the fats.

Eating all your meals is always the best bet on a diet. Have you considered eating macrobiotic? That might be a good way to lose some weight quickly and stay healthy.