Let's say I want to eat dessert after a meal (with the recommended amount of fat, of course). It makes sense that Alli would have the most effect the closer in time in taking it and eating dessert. But let's say I'm trying to be a more thoughtful eater. When does the window close and Alli is not effective anymore?

I would just say take it with the meal. I think Alli is supposed to be effective all day, though. If not, they would increase the number of times you take it in a day.

thanks for your thought
i'm thinking that if you're supposed to take it three times a day, it has to wear off at some point
i want to know what that point is

I know what you mean. A friend of mine is diabetic, and she takes a medication with each meal that does something like alli, and prevents sugars from being absorbed into the bloodstream. It's effective for about an hour max, and gets less effective as time goes on. So if we go out to eat and have a nice leisurely meal, nothing that she has at the end is really affected by her medication.

I guess I should cut down on my snacking so that I do not get extra fat inbetween meals while Alli is not fully effective. What do you think?

Well, perhaps in general that's a good idea, but in the context of the question I asked, only if your snacks have a lot of fat in them.

You are supposed to take it within an hour after a meal, so I guess that is the window.

Yes, you take it with the meal or within an hour after the meal, and no later. You are not supposed to take it in advance of eating.

I am keeping to fat free or nearly fat free snacks (fruit, ff yogurts etc.)

Kitty