How the calorie deficit is worked out
To lose weight, you eat fewer calories than you burn. A common estimate is that a pound of body fat holds about 3,500 calories, so losing 1 lb a week takes a deficit of about 500 calories a day.
Example: a 30-year-old man, 5 ft 9 in and 165 lb, exercising 3 to 5 days a week, maintains on about 2,633 calories. To lose 10 lb in 10 weeks, he needs a 500-calorie daily deficit, so about 2,133 calories a day, a pace of 1 lb a week.
Keeping it realistic
- Aim for 0.5% to 1% of body weight a week. Faster loss is harder to keep up and costs more muscle.
- Don't go below about 1,200 calories a day for women or 1,500 for men without medical supervision.
- Weight loss slows as you get lighter, because your maintenance calories fall. Recalculate every 10 lb or so.
- The 3,500-calorie rule is a simplification; research models like the NIH Body Weight Planner account for your body adapting over time.
Set your protein with the protein calculator, and see the whole timeline with the weight loss calculator.
Frequently asked questions
How big should my calorie deficit be?
About 300 to 500 calories a day suits most people: roughly 0.5 to 1 lb a week. Larger deficits are harder to sustain.
Can I lose weight without counting calories?
Yes, by changing habits that lower intake, such as more protein and fiber, fewer sugary drinks and more activity. The deficit still has to happen; counting just makes it measurable.
Why am I not losing weight in a calorie deficit?
Usually because intake is underestimated or activity overestimated. Water retention can also hide fat loss for a week or two. Track for 2 to 3 weeks before adjusting.
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