Daily Calorie and Protein Targets

Training decides what the body is asked to do; energy and protein decide what it can build or keep. A program aimed at losing fat or gaining muscle works only as well as the intake behind it. This document sets out how daily calorie and protein targets are estimated from a profile and a goal, and how far to trust the estimate.

Resting energy expenditure

Resting energy expenditure is estimated with the Mifflin–St Jeor equation, which in a systematic comparison of predictive equations came within 10% of measured values in more people, lean and obese, than any other equation.

Sex	Resting energy expenditure (kcal/day)
Men	10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5
Women	10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161

When sex is not given, the constant is the midpoint of the two, −78.

Activity

Total energy expenditure is resting energy expenditure multiplied by a physical activity level. International energy requirement reports group lifestyles into three bands: sedentary or light activity 1.40–1.69, active or moderately active 1.70–1.99, vigorous 2.00–2.40.

Training sessions per week	Activity level used
0–2	1.55, light
3–4	1.75, moderately active
5 or more	1.90, active

Training sessions are strength and cardio days together. A vigorous level is not assigned from training alone: it describes hours of hard physical work every day, which a training schedule does not show.

Calories by goal

Goal	Daily calories
Fat loss	80% of maintenance
Muscle gain	110% of maintenance
Strength, general fitness, endurance	maintenance

Fat loss. Fat loss is driven by a sustained deficit, and slower rates of loss preserve more lean mass. In elite athletes, cutting intake by about a fifth produced a weekly loss near 0.7% of body weight and lean mass increased, while a deeper cut lost weight faster and gained no lean mass. For lean, trained people the recommended pace is roughly 0.5–1% of body weight per week.

Muscle gain. Gaining lean mass is driven by a sustained surplus. Recommendations for natural lifters are a surplus of about 10–20% with a weight gain near 0.25–0.5% of body weight per week; the low end limits fat gain.

Everything else. Strength, general fitness and endurance programs eat at maintenance.

Protein

Goal	Daily protein
Fat loss, body fat known	2.3 g per kg of fat-free mass
Fat loss, body fat unknown	2.0 g per kg of body weight
Every other goal	1.6 g per kg of body weight, up to 2.2

Across the research on protein and resistance training, gains in fat-free mass stopped increasing beyond about 1.6 g per kg per day. A daily intake of 1.4–2.0 g per kg is sufficient for most exercising people, and ranges up to 2.2 g per kg are recommended for lifters trying to gain muscle. In a deficit, lean, resistance-trained people may need 2.3–3.1 g per kg of fat-free mass to keep their muscle. Without a body-fat estimate, fat-free mass is unknown, so the target falls back to the top of the general range per kg of body weight.

A worked example

A 30-year-old man, 180 cm and 80 kg, training four days a week to build muscle:

• resting energy expenditure: 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 1,780 kcal;
• maintenance: 1,780 × 1.75 = 3,115 kcal, shown as 3,100;
• target: 3,115 × 1.10 = 3,427 kcal, shown as 3,450;
• protein: 1.6 × 80 = 128 g, shown as 130 g, up to 175 g.

The same man cutting fat eats 2,500 kcal (80% of maintenance, rounded) and, without a body-fat estimate, 160 g of protein.

How far to trust the numbers

These are starting points, rounded to the nearest 50 kcal and 5 g. An equation that is within 10% for most people is still 10% away for some. The real test is the scale: if weight does not move in the intended direction at the intended pace over two to three weeks, intake changes, not the goal.

• Very lean or very muscular people burn more at rest than a weight-based equation predicts, so their maintenance is usually higher than the estimate.
• People with obesity are estimated less accurately by every equation; a body-fat estimate makes the protein target more realistic because it is counted on fat-free mass.
• Hard physical jobs raise daily expenditure beyond what training days describe. The activity level here counts training only, so the estimate is low for them.
• Weekly averages matter more than single days. Training days and rest days can differ; what decides the direction of body weight is the average across the week.