Weight Loss 101: How to Calculate a Calorie Deficit

To lose weight, you have to eat fewer calories than your body burns each day. It seems simple enough. What's not so easy is actually doing it. How do you know if you're actually eating fewer calories than your body burns? Exactly what size of "calorie deficit" should you aim for? And how can you make sure you're hitting the mark?

These are the questions you must answer to get on track toward your weight-loss goals. So let's answer them.

The Calorie Deficit Sweet Spot

The easiest way to ensure you eat fewer calories than you burn is, of course, to eat very little. If you have an apple for breakfast, a small salad for lunch, a piece of toast for dinner and nothing else, you can be pretty sure you're maintaining a calorie deficit. But you'll also be miserable with hunger and a lack of energy.

The optimal calorie deficit is large enough to stimulate steady fat loss, but not so large that you're always hungry and lethargic. Avoiding a calorie deficit that is too large is even more important for athletes, who need to keep their muscles well-fueled for training. The calorie deficit "sweet spot" for athletes is 300 to 500 calories per day.

Do the Math

Your ultimate goal is to figure out exactly how many calories to eat daily to lose weight without being hungry and lethargic and without sabotaging your training. To do that you need to figure out how many calories you burn each day and then subtract your target deficit of 300 to 500 calories from that number.

There are two components to your total calories burned daily: calories burned at rest and calories burned in workouts.

To begin, add up the total number of hours you train in a typical week and divide that number by seven to yield the average number of hours you train daily. For example, suppose you train seven hours per week on average. This works out to one hour per day. Next, multiply this number by your body weight in pounds and the average number of calories you burn per pound of body weight per hour of training. The average number of calories you burn per hour of training is influenced by your speed. Use this table to get the appropriate multiplier.

Training Speed

Calories per pound per hour

Slower (run 11:00/mile)

4

Average (9:30/mile)

5

Faster (7:00/mile)

6

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