I second the dietician. I'd much rather see people making an effort with their diets than being forced to eat a low fat diet in fear of pooing ones' self. After all, what do you really learn from Orlistat? You don't learn about portion control, or self control or even about balanced diets, you just learn what foods to avoid - which, isn't actually that healthy imo.
I again, suggest a slimming club such as weightwatchers. You will learn how to eat a low fat and low calorie diet but using a points system (which, in my experience, has been far less complicated than working out the calories in everything). You learn about just how much exercise is required to burn off that sandwich and you learn about portion control, self control and also how to maintain it without falling off the proverbial wagon.
I honestly don't mean to go on, but I can think of a hundred reasons why a dietician or a slimming club would be a better, more sensible alternative to Orlistat.