In short
Protein and carbohydrate each carry 4 calories per gram; fat carries 9. For a healthy adult the common target ranges are 1.6-2.2 g of protein and 0.8-1 g of fat per kilogram of body weight, with the remaining calories coming from carbohydrate. Total calories decide whether your weight changes; the macro split decides satiety, muscle retention and training performance.
Three macros, three different densities
Macronutrients are the three components of food that carry energy, and they contain different amounts of it per gram. That difference alone explains why two meals of identical weight can carry wildly different calorie loads.
| Macro | Calories per gram | Main role |
|---|---|---|
| Protein | 4 kcal | Tissue repair, muscle retention, satiety |
| Carbohydrate | 4 kcal | Primary energy source, training performance |
| Fat | 9 kcal | Hormone production, absorption of fat-soluble vitamins |
| (Alcohol) | 7 kcal | Provides energy, carries no nutritional value |
Protein: the macro that changes the most
In a calorie deficit, protein is the single most important variable for limiting muscle loss. It also has the strongest effect on satiety of the three, and it costs the most energy to digest — roughly 20-30% of the protein you eat is burned in processing it.
The common recommendation for healthy adults is 1.6-2.2 grams per kilogram of body weight. For a 70 kg person that is 112-154 grams a day, or 450-620 calories. Sitting near the upper end of that range usually makes sense while losing weight.
- Spreading 25-40 g across each main meal works better than stacking it all into one.
- Eggs, yoghurt, chicken, fish, pulses and lentils are practical sources.
- On a plant-based diet, varying sources across the day rounds out the amino acid profile.
Fat: not low, just adequate
Fat was blamed for weight gain for decades; we now know that was wrong. Fat is required for hormone production, and vitamins A, D, E and K are not absorbed without it. Very low-fat diets can cause problems for exactly that reason.
A practical floor is around 0.8 grams per kilogram — about 56 grams, or 500 calories, for a 70 kg person. The source matters more than the amount: olive oil, avocado, walnuts, almonds and oily fish should come first.
Carbohydrate: whatever is left
Once protein and fat targets are set, the remaining calories come from carbohydrate. Working through a 70 kg, 2,000-calorie example: subtract 140 g of protein (560 kcal) and 60 g of fat (540 kcal) and you are left with 900 calories, or roughly 225 g of carbohydrate.
What really sets the carbohydrate figure is activity. Someone training hard and often performs better on more of it; on a sedentary day the same amount is simply unnecessary. Favouring whole grains, pulses, vegetables and fruit also raises fibre intake without any extra effort.
How much does the split really matter?
Controlled trials have repeatedly shown that when calories are matched, different macro splits produce little difference in weight loss. A low-carbohydrate diet has no intrinsic advantage over a low-fat one.
The difference shows up indirectly. If a higher-protein plan keeps you fuller, you eat less; a plan that bans everything you enjoy gets abandoned in a fortnight. The right split is the one you can sustain while still hitting your protein target.
Frequently asked questions
Can I just count calories and ignore macros?
For weight change, largely yes. But if you want to retain muscle, perform in training or fix a satiety problem, tracking at least protein makes a noticeable difference.
Do carbs at night cause weight gain?
No. Meal timing has not been shown to have a meaningful effect on weight when total calories are held constant. For some people, carbohydrate in the evening even improves sleep.
Do I need protein powder?
No — it is a convenience, not a requirement. If you can hit your target with ordinary food there is no added benefit; if reaching 140 grams a day through meals feels like a struggle, it makes the job easier.
Sources
- 1.
Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine, 52(6):376-384, 2018.
- 2.
Institute of Medicine (US), Food and Nutrition Board Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press, Washington DC, 2005.
- 3.
Johnston BC, Kanters S, Bandayrel K, et al. Comparison of weight loss among named diet programs in overweight and obese adults: a meta-analysis. JAMA, 312(9):923-933, 2014.