In fact, no one can gain weight from one tablet. And the myth is the belief that lithium provokes the accumulation of water in the body and, consequently, obesity. We can not, however, deny the fact that many people gain weight by taking antidepressants. Many drugs, especially in the field of psychiatry, stimulate appetite. This is especially famous for olanzapine, lithium, and most of antidepressants. A person eats more than usual, and therefore is fattening. So when you start the treatment, it is important to control your weight. After all, it is much easier to maintain than to lose it.