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Metabolic basicsEvidence-basedLesson 17 of 20

Protein: the satiety macronutrient

Protein keeps you full, protects muscle while you lose fat, and costs energy just to digest.

4 min+20 XP

Based on 2 referenced sourcesUSDA/HHSWHO

Why protein fills you up

Protein triggers the release of GLP-1 and peptide YY — hormones that tell your brain you've eaten enough — while lowering ghrelin, the hunger hormone. In practice, a breakfast with 30g of protein reduces how much people eat later in the day.

Protecting muscle in a deficit

When you eat fewer calories than you burn, your body can break down muscle as well as fat. Eating 1.6–2.2g of protein per kilogram of body weight, paired with resistance training, tells your body to keep the muscle and use the fat.

The thermic effect

About 20–30% of the calories in protein are used up digesting and processing it, compared to 5–10% for carbohydrate and 0–3% for fat. A higher-protein diet quietly increases your daily burn.

Key takeaways

  • Aim to anchor every meal with a protein source.
  • 1.6–2.2g per kg body weight protects muscle during fat loss.
  • Protein has the highest thermic effect of all macronutrients.

Check your understanding

2 questions · answer to earn XP

1. Roughly how much of protein's calories are burned during digestion?

2. Why does protein matter during a calorie deficit?

Evidence & sources

This lesson reflects guidance from recognised health bodies and peer-reviewed research.

How we grade evidence
  • Guideline — recommendations from national or global health bodies.
  • Systematic review — pooled findings across many studies.
  • Cohort study — long-term observation of large groups of people.
  • Government data — official statistics and public health programmes.

For education purposes only — not intended to diagnose, treat or replace medical advice.