How many calories do I need to burn to lose 20 pounds?

According to the Mayo Clinic, 70,000 calories of fat equal 20 pounds, as each pound is equivalent to 3,500 calories. However, it is unlikely this amount of weight loss would be purely fat, as water and even muscle are often lost during significant weight loss.

The Mayo Clinic further states that weight loss is a matter of consuming less calories than those that are expended. Each gram of carbohydrates and protein contains around 4 calories, while a gram of fat contains 9 calories. Effective methods of reducing calories include substituting high-calorie foods for low-calorie versions, reducing portion size and forgoing high-calorie, low-nutrition foods altogether.