Well, technically speaking, slimming
pills do make you thinner, more haggard and unhealthy. They make you
lose weight by suppressing appetite, causing indigestion, preventing absorption of nutrients, and other such drastic routes. Though you lose weight, the weight loss is not healthy. Yes, there are drugs to treat morbid obesity, which work more or less on similar principles but in a more scientific way, and are useful only in those really obese.