Protein is the only macronutrient your body cannot store in a meaningful reserve for later use. Unlike body fat (stored energy) or glycogen (stored carbohydrate), there is no dedicated protein storage system — your body uses muscle tissue as a functional reserve. This means daily protein intake isn't just a performance variable; it directly determines whether your body has the raw materials it needs to repair tissue, produce enzymes and hormones, support immune function, and build or maintain muscle mass. Getting your target right — and consistently hitting it — is one of the highest-leverage nutrition habits you can build.
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Muscle Protein Synthesis
Dietary protein provides the amino acids required to repair and build muscle tissue after exercise. Consistently hitting your daily target is the primary determinant of muscle retention during fat loss and muscle gain during a bulk.
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Highest Thermic Effect
Protein has a thermic effect of 25–30% — meaning your body burns 25–30 kcal just digesting 100 kcal of protein. This is 3–5× higher than carbohydrates or fat, making protein the most metabolically active macronutrient.
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Satiety and Hunger
Protein is the most satiating macronutrient per calorie. High-protein diets consistently reduce spontaneous caloric intake in research studies, making protein the most effective lever for controlling hunger without counting every calorie.
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Enzyme and Hormone Production
All enzymes, most hormones (including insulin and growth hormone), and immune antibodies are proteins. Adequate intake supports optimal metabolic function, immune defence, and hormonal balance — not just muscle.
Frequently Asked Questions
How much protein do I need per day?
It depends on your weight, activity level, and goal. For sedentary adults, the minimum is 0.8g per kg of bodyweight. For active individuals, 1.4–1.7g/kg is well-supported. For those actively trying to build muscle or maintain it during fat loss, 1.6–2.4g/kg is the evidence-backed range. This calculator applies these thresholds based on your inputs.
Does protein timing matter?
Less than total daily intake, but it's not irrelevant. Research supports spreading protein across 3–4 meals of 30–40g each, as muscle protein synthesis (MPS) has a per-meal ceiling. Post-workout protein (within 1–2 hours) is beneficial but not the decisive factor most gym culture suggests — total daily protein matters more than any specific timing window.
Can you eat too much protein?
For healthy adults with functioning kidneys, current evidence does not support harm from high protein intakes (even above 3g/kg). The kidney disease concern applies to people with pre-existing kidney conditions, not healthy individuals. Practically, the main downside of very high protein intake is that it displaces other foods and can make hitting calorie targets difficult.
What are the best high-protein foods?
By protein density (per 100g cooked): chicken breast (~31g), tuna (~30g), turkey breast (~29g), tempeh (~19g), edamame (~11g), cottage cheese (~11g), Greek yoghurt (~10g), eggs (~13g per 100g), lentils (~9g cooked), tofu (~8g). Combining multiple sources across meals ensures a complete amino acid profile, especially important for plant-based diets.
Do protein needs change with age?
Yes — older adults (50+) require more dietary protein than younger adults to achieve the same muscle protein synthesis response. This is called anabolic resistance. Research supports a target of 1.2–1.6g/kg minimum for adults over 50, rising toward 2.0g/kg for those doing resistance training. Adequate protein becomes more — not less — important as we age for preserving muscle and function.
Should I eat more protein on rest days?
Yes — muscle repair and protein synthesis continue for 24–48 hours after training, including rest days. There's no physiological basis for reducing protein on non-training days. Keep intake consistent across the week. If anything, slightly higher protein on rest days can support recovery from the previous session.