Look up Alternate Day Modified Fasting. There's been some research by a nutritionist named Krista Varady on it. It's pretty simple: every other day, only eat 500 calories, then do whatever the next day. It's much easier than a total fast and 90%+ of the weight you lose is fat (compared to ~75% for simply counting calories). You can workout on the days that you eat. For maintaining (rather than losing) weight, you can increase the calories on the fast day.