The Physics of Fat Loss
You cannot out-train a bad diet. You cannot supplement your way past thermodynamics. To lose body fat, you must eat fewer calories than you burn. This is not negotiable, not complicated in theory, and brutally difficult in practice. The math is simple. The execution is where it gets hard.
A deficit of 3,500 calories equals approximately one pound of body fat. That's 500 calories per day below your maintenance level to lose one pound per week. It's also about the maximum safe rate for most people without risking muscle loss, nutrient deficiencies, and metabolic slowdown.
How Big Should Your Deficit Be?
The answer depends on how much body fat you have and how aggressive you want to go:
- Small deficit (10-15% below TDEE): Slow but sustainable. Ideal for longer cuts, people with less body fat, or those who want to preserve maximum muscle.
- Moderate deficit (20-25% below TDEE): The sweet spot for most people. 0.5-1% bodyweight loss per week. Manageable hunger, good muscle preservation with adequate protein.
- Large deficit (30%+): Fast results but risky. Only for those with significant body fat to lose. High chance of muscle loss, extreme hunger, and metabolic adaptation.
Don't Cut Too Aggressively
The most common mistake beginners make is going too hard too fast. A 1,000-calorie deficit sounds good on paper — you'd lose two pounds per week! In reality, you'll be starving, lose muscle along with fat, crash your metabolism, and quit after three weeks.
Start with a 15-20% deficit. If you're hungry all the time, add 100-200 calories. The best diet is one you can stick to, not the most aggressive one you can tolerate for two weeks.
Use our calorie deficit calculator to find your target intake. Pair it with adequate protein (1.6-2.2g per kg bodyweight) and resistance training to minimize muscle loss.