When people think about losing fat, they usually cut calories and crank up cardio. That works, but it often makes you hungry, tired, and weaker. Protein fixes a lot of those problems.
The Thermic Effect of Protein
Not all calories are equal when your body processes them. Protein takes more energy to digest than carbs or fat—about 20–30% of its calories are burned off just in digestion. Compare that to carbs (5–10%) or fat (0–3%). That means if you eat 100 calories of protein, you’re only netting ~70–80.
Satiety: Staying Full on Fewer Calories
Protein is the most filling macronutrient. Meals higher in protein reduce ghrelin (the “hunger hormone”) and increase satiety hormones like peptide YY (Leidy et al. 2015). In plain terms: you stay full longer and are less likely to snack mindlessly.
Muscle Preservation During a Cut
When you drop calories, you don’t just lose fat—you risk losing muscle. Protein intake helps protect lean mass, especially if you’re lifting weights. Keeping muscle matters, because muscle burns more energy at rest and keeps your metabolism higher.
Protein vs. “Eat Less, Move More”
A lot of fat loss advice stops at “calorie deficit.” That’s technically true, but it ignores compliance. A high-protein diet makes staying in a deficit easier because you’re less hungry, you have more stable energy, and you don’t feel like you’re starving all the time (Weigle et al. 2005).
Practical Targets
- Baseline: At least 1.6 g protein per kg of body weight (Morton et al. 2018).
- Aggressive fat loss: 2.0–2.4 g/kg is safer for holding onto muscle (Helms et al. 2014).
- Spread across meals. A good target is at least 50g of protein per meal.
Bottom Line
Protein isn’t magic. The math is still largely about calorie in vs. calorie out. You still need a calorie deficit to lose fat. But compared to carbs and fat, protein gives you more satiety, higher energy cost of digestion, and muscle protection. If you’re dieting without adequate protein, you’re making it harder than it needs to be.