Carlos, I don't think Alli is the best solution. All it does is prevent some of the fat you eat being absorbed. Betsy is right about portion sizes. I have been observing people eating in restaurants etc while I sip my water. Some of what I have noticed is as follows:
We eat out of habit e.g "oh its one o clock, time for lunch" So we should eat only when we really feel hungry.
We eat soooo fast. We wolf down food. I say stop, savour and swallow before the next bite.
We must clear the plate and portions are huge. If we eat more slowly, then we might fill up and stop before the plate is empty.
I think these are some of the things we need to consider so that we don't go back to our old habits.