Most people eat enough protein
to survive. Almost nobody eats
enough to thrive.

What protein actually does

Protein is not just "the muscle thing." Every cell in your body contains protein. It's the structural material for muscle, bone, skin, hair, and nails. It's the raw material for enzymes (which drive every chemical reaction in your body), antibodies (immune function), hormones (including insulin and growth hormone), and neurotransmitters (including dopamine and serotonin).

From a body composition standpoint, protein does several things that no other macronutrient can:

• It has the highest thermic effect of any food — your body burns approximately 20–30% of the calories in protein just digesting it. Fat burns 0–3%, carbohydrates 5–10%.
• It's the most satiating macronutrient — protein suppresses ghrelin (hunger hormone) more effectively than carbohydrates or fat, and increases peptide YY (satiety hormone)
• It preserves muscle during calorie restriction — when you're in a calorie deficit, adequate protein intake is what determines whether you lose fat or a mixture of fat and muscle
• It drives muscle protein synthesis (MPS) — the process by which your muscle fibres are repaired and built larger after training

How much do you actually need?

The science here is now well-established. A 2017 meta-analysis published in the British Journal of Sports Medicine — examining 49 studies covering 1,800 participants — found that 1.62g of protein per kg of bodyweight per day was the point at which muscle gains were maximised. Beyond approximately 2.2g/kg, additional protein provided diminishing returns for muscle building.

Complete vs incomplete protein — the amino acid picture

Proteins are made of amino acids. There are 20 amino acids in total, nine of which are "essential" — meaning your body cannot synthesise them and must obtain them from food. A "complete" protein contains all nine essential amino acids in adequate quantities.

• Complete proteins: All animal products (meat, fish, eggs, dairy, whey). Also soy, quinoa, and buckwheat from plant sources.
• Incomplete proteins: Most plant proteins (legumes, nuts, grains, vegetables) — lacking one or more essential amino acids. This doesn't mean they're useless; it means you need to combine sources throughout the day to cover all nine amino acids.

The most critical amino acid for muscle protein synthesis is leucine. It acts as the trigger for MPS. Animal proteins are generally far higher in leucine than plant proteins — which is why gram-for-gram, animal protein tends to be more effective for muscle building. You need roughly 2.5–3g of leucine per meal to maximally stimulate MPS.

Best protein sources — the numbers per 100g

Plant vs animal protein — the honest comparison

This is a topic that attracts a lot of ideology. Here's the honest science:

• Animal protein is generally superior for muscle building — higher leucine content, complete amino acid profile, better bioavailability (digestibility). This is not a matter of opinion; it's well-documented in the research.
• Plant protein can work for muscle building — but requires higher total intake to account for lower leucine content and reduced bioavailability. Aim for the upper end of the protein range (2.0–2.4g/kg) if relying primarily on plant sources.
• Combining plant proteins matters — rice and peas together provide a complete amino acid profile. This is why many plant-based protein powders use a rice-pea blend.
• Both can support a healthy diet — the research on overall health outcomes doesn't cleanly favour one over the other when protein intake is adequate. The quality of the overall diet matters more than this single variable.

Protein timing — does it matter?

The "anabolic window" (the idea that you must consume protein within 30 minutes of training) has been significantly overstated. More recent meta-analyses suggest the total daily intake matters more than specific timing. That said, consuming 20–40g of complete protein within 2 hours post-workout does provide a meaningful stimulus for muscle protein synthesis, and there's no reason not to take advantage of this.