Work out how many calories to eat each day and how to split them between protein, carbohydrate and fat, based on your body, activity level and goal.
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How the targets are set
- Resting energy: estimated with the Mifflin-St Jeor equation, from your sex, age, height and weight.
- Daily energy: multiplied by an activity factor to estimate your maintenance calories.
- Goal: about 20% fewer calories to lose fat, or about 10% more to build muscle.
- Macros: protein from your body weight, about 28% of calories from fat, and the rest from carbohydrate.
Worked example
A 32-year-old woman, 165 cm and 68 kg, with light exercise, has maintenance needs of about 1,912 kcal. To lose fat at a steady pace she’d aim for about 1,529 kcal a day: 109 g protein, 165 g carbohydrate and 48 g fat.
A loss of about 0.5 kg a week is a realistic, sustainable target for most people. Faster weight loss tends to cost muscle and is harder to keep up.
Why protein matters
Eating enough protein helps keep muscle while you lose fat and helps you feel full. Research on active people commonly supports 1.6 g per kg of body weight a day, and up to about 2 g per kg when lifting weights in a calorie deficit.
A note on safety
These are estimates for healthy adults. If you’re pregnant or breastfeeding, under 18, have a medical condition, or have a history of eating disorders, talk to a GP or registered dietitian before changing how you eat.
Frequently asked questions
What are macros?
Macronutrients: protein, carbohydrate and fat, the parts of food that provide calories. Protein and carbohydrate have about 4 kcal per gram and fat about 9.
How much protein do I need?
The UK reference intake is 0.75 g per kg for adults, but active people and those losing fat often benefit from around 1.6 g per kg.
How accurate is the calorie estimate?
Equations can be off by 10% or more for an individual. Track your weight for a few weeks and adjust.
Should I count macros?
Not necessarily. Some people find it helpful; others do better with simpler habits like more protein and vegetables at each meal.
Sources
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