Mechanism One: The Thermic Effect of Food (TEF)
| Macronutrient | Calories Burned Digesting It |
|---|---|
| Protein | 20–30% of its own calories |
| Carbohydrates | 5–10% of its own calories |
| Fat | 0–3% of its own calories |
This means eating 100 calories of protein effectively "costs" 20–30 of those calories just to digest and process, versus only 5–10 for carbs. Swapping some carbs or fat for protein at the same total calorie intake genuinely raises the total energy your body spends on digestion — a real, if modest, metabolic advantage.
Mechanism Two: Muscle Preservation
The bigger effect is indirect. Adequate protein intake (1.6–2.2 g/kg bodyweight) supports muscle maintenance and growth, especially alongside resistance training. Since muscle drives a meaningful share of your BMR, protein’s biggest metabolic contribution over the long term is protecting and building the tissue that keeps your BMR higher — not the direct digestion cost.
Protein During a Calorie Deficit
1 It protects muscle while you’re cutting
Higher protein intake during a deficit consistently shows better muscle retention compared to lower-protein diets at the same calorie level, which limits how much your BMR drops as you lose weight.
2 It supports satiety
Protein is generally the most filling macronutrient per calorie, which can make sticking to a deficit easier — an indirect but meaningful benefit for weight management.
How Much Protein Do You Actually Need?
Check your personalised gram target using the macro breakdown on our calculator, which sets protein at 30% of your calorie intake by default to protect muscle across weight loss, maintenance and muscle-gain goals.
Frequently Asked Questions
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