How the macros are worked out
First the calories: what you burn (Mifflin–St Jeor with your activity), minus 500 kcal to lose weight or plus 300 to gain. Then protein, because it matters most: 1.8 g per kg of body weight when you lose or build, 1.2 g/kg to keep your weight — counted on an adjusted weight over a BMI of 30.
Fat gets about 30% of the calories, never under 0.6 g per kg: the body needs it for hormones and to take up vitamins A, D, E and K. What is left goes to carbohydrates, the body's easiest fuel.
Ranges, not exact numbers
Health bodies give wide healthy ranges: 10–35% of energy from protein, 20–35% from fat and 45–65% from carbohydrates. Inside them, the split matters much less than total calories and food quality. Hit your protein and calories most days and let fat and carbs swing with what you like to eat.
Where the carbs come from counts: vegetables, fruit, beans and whole grains bring fibre and keep you full; sugar and white flour do neither.
Grams on the plate
Protein and carbs give 4 kcal per gram, fat 9. 30 g of protein is a palm of chicken or fish; 15 g of fat is a tablespoon of oil; 50 g of carbs is about a cup and a half of cooked rice. Weighing food for a few days teaches the eye — after that, a photo is enough.
Questions
- What is a good macro split for weight loss?
- There is no single best split. Keep protein high (around 1.6–2.2 g per kg), stay in a calorie deficit and spread the rest between fat and carbs as you like — studies find diets with different splits lose about the same weight when calories match.
- Do I need to hit my macros exactly?
- No. Protein within 10–20 g and calories within 100–200 kcal of the target on most days is plenty. Fat and carbs can move around freely.
- Is a low-carb diet better?
- Only if it is easier for you to keep. Low-carb and low-fat diets lose about the same in the long run; the one you can stick with wins.
- Do macros change if I train?
- Training raises your calories through the activity level, and strength training is a reason to keep protein at the higher end. Endurance athletes usually need more carbohydrate.
Sources
- Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press, 2005.
- EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on Dietary Reference Values for fats. EFSA Journal, 2010.
- Jäger R et al. International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr, 2017.
- Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr, 1990.