Conventional wisdom says you should lose no more than two pounds a week, which you can accomplish with a 1200 net calorie diet, i.e. consuming 1200 calories plus any calories you burn from exercise.

Using C25K, a running app, and MyFitnessPal, a calorie tracking app, I lost 38 pounds in four months last year. I'm 5'7", 26 years old, and went from 192 to 154.