What is a calorie deficit?
Your body uses energy every day, at rest and when you move. A calorie deficit means eating a bit less than that, so your body makes up the difference from stored energy.
The 2013 obesity guideline from the American Heart Association, the American College of Cardiology and The Obesity Society says weight loss needs an energy deficit, and that a deficit of 500 calories a day or more typically means about 1,200–1,500 calories a day for women and 1,500–1,800 for men.
Why the minimum is 1,200
Very low targets are hard to stick with and make it harder to get enough protein and nutrients, so this calculator, like our quiz, uses a minimum target of 1,200 calories for women and 1,500 for men. That minimum is a rule of our tools, not an individual safety assessment. If your maintenance is close to it, the gap will be much smaller than 500; if it is at or below it, no target is shown.
How fast will I see results?
Hall and colleagues showed that body weight responds dynamically to changes in intake, so the fixed “3,500 calories equals 1 pound” rule does not reliably predict weight change over time. This calculator does not predict when you will see results.
Keeping muscle while you lose
Two things help: enough protein, and using your muscles. The calculator shows Coach Josh’s protein range (your goal weight in pounds × 0.9 to 1.0, in grams). U.S. guidelines also advise muscle-strengthening activity on 2 or more days a week, alongside walking.
