Calculate Max Fat Loss Rate

The information and calculators on this page will help you figure out the maximum amount of fat loss to aim for before you begin to adversly affect your muscle mass.

You can only lose fat so fast before you start losing muscle too. Although there are many factors that affect how much fat your body burns for energy based on caloric intake, the formulas and calculator below will provide a good starting point for you to begin your weight loss effort.

The 20% Method

The first thing you need to do is figure out your total daily energy expenditure (TDEE). Keep in mind that any TDEE calcualtor will only provide an estimate. It's up to you to stick to that number, observe the results, and adjust accordingly.

The 20% method is easy: take 20% of your TDEE as your caloric deficit.

Example: a 6-foot tall, 25 year old, 200 pound man who is lightly active has a TDEE of 2,711. Multiple 2,711 by 20% to get 540. So that's the daily deficit, to be adjusted every week or two to account for weight loss.

Body Weight Method

Another and perhaps more accurate method is to use your body weight, based on the calculation that maintenance for each pound of body weight is 14 - 16 calories (26.2 - 35.2 per kg). The higher your lean mass, the closer you are to the top of this range. Eating under that amount would result in weight loss. We again use the 20% rule, this time applying it to maintenance calories as determined by your weight.

Fat to Energy Conversion

Now we're getting a bit more complicated. This method uses how much fat you are carrying to determine the your maximum daily caloric deficit. There's some differing information here. A study came out that indicated the maximum rate your body can extract energy from stored fatis 31 calories per day per pound of fat.

However, the author of that study, Professor Seymour Alpert, later revised taht to 22 calories per pound of fat per day, saying:

The value used of 31 calories per pound is correct only if there is no energy loss to activity. In the original paper, I took a value of activity losses from some of my previous work, but I have recently developed a much better way to estimate activity losses which changes the maximum practical value for the idealized value of maximum loss from fat alone to the actual loss to only 22 kcal/d lb. This mean that it is very hard to lose fat alone. That is life.

So for the calculator below I'm using both values: 31 calories per pound to represent idealized and 22 calories per pound for real world.