Calorie Deficit Calculator

The 3,500-Calorie Rule (and Its Limits)

One pound of body fat contains approximately 3,500 calories of stored energy. To lose 1 pound per week, you need a total weekly deficit of 3,500 calories -- or about 500 calories per day below your TDEE (Total Daily Energy Expenditure). This is a useful starting point, but your body is more complex than simple subtraction.

Why Deficits Slow Down Over Time

As you lose weight, your TDEE decreases because there is less of you to maintain. A 190-pound person burns more calories at rest than a 175-pound person. This means the same 500-calorie deficit produces slower weight loss as you approach your goal. The solution: recalculate your TDEE every 5-10 pounds lost.

Safe Deficit Guidelines

• 0.5-1% of body weight per week is generally safe and preserves lean muscle mass
• Never go below 1,200 cal/day (women) or 1,500 cal/day (men) without medical supervision
• Larger deficits (over 1,000 cal/day) increase the risk of muscle loss, nutrient deficiency, and metabolic adaptation
• Diet breaks every 6-8 weeks at maintenance calories help prevent metabolic slowdown and improve long-term adherence
• Protein intake should remain high (0.7-1.0g per lb of body weight) during a deficit to preserve muscle

The Role of Exercise

You can create a deficit through diet alone, exercise alone, or a combination. Research consistently shows that diet creates the majority of the deficit while exercise preserves muscle mass, improves body composition, and supports metabolic health. The most effective approach combines a moderate calorie reduction (300-500 cal/day from food) with regular resistance training.