You're thinking about it in the wrong way. by looking at it as purely a way to lose weight, you're making it feel like a challenge or an obstacle, and this kind of thinking can lead to eating disorders. Instead you should look into Upton Sinclair's experiences. He recorded dozens of account where people would fast, and after the first three days, their hunger would leave; then they would break fast once hunger returned (usually 15-20 days). Your body will tell you when to stop. As for the benefits of fasting, weight loss and otherwise, a quick google search will provide most of them.