Losing weight is easy, absent some real medical problem. Ready? Here we go:

If you eat more calories than you burn, you will gain weight.

If you burn more calories than you eat, you will lose weight.

The more of a difference between burning and eating, the faster you will gain or lose weight.

Now, burning calories doesn’t just mean exercise, although that’s an important part of it. It’s also what you burn just walking around during the day. Or sitting in front of the computer. Or sleeping. What this means is if you take in 2000 calories in a day, you don’t have to burn 2000 calories doing exercise….

“Knowing your Daily Calorie Needs is more than knowing how many calories your body needs for its basic physiologic functions (known as your Resting Metabolic Rate or BMR). It’s also important to know how many calories your body needs to maintain certain daily activities. By combining your resting metabolic rate and your daily activity level, you will get the total number of calories your body needs during the day.”

24hr Fitness daily calorie needs calculator. A tip: if you’re not sure what activity level you should use, calculate each in turn and make a separate note of them, so you can get a sense of both the range you should be in on a given day, but also giving you some flexibility — if I want to eat that stuff I should incorporate some exercise.