Hmmmm....
You can drink 4 and, if you're really, really, really morbidly obese, it's probably best to start with 4 as this is still a major cut in calories from what you're probably used to knocking down. If you consult the booklet that comes with the batch, I think you'll find it states that 4 can be consumed.
Perhaps you could start with 4 and move down to 3 as things get a little easier?