How do you set your macros?

The order matters more than the numbers

Macronutrients are the three things calories come from: protein and carbohydrate at four kilocalories per gram, fat at nine. Setting macros means deciding how many grams of each to eat, and the usual mistake is deciding all three at once as percentages.

A better order is to set protein first, then fat, then let carbohydrate absorb whatever calories are left. That ordering exists because the three have different jobs. Protein has a requirement that scales with your body, not with your calorie intake. Fat has a floor below which hormonal and absorption problems begin. Carbohydrate has neither — it is the flexible remainder, and treating it as such is what makes the other two possible to hit.

This is also why percentage splits like 40/30/30 tend to fail. A percentage of calories is a moving target: cut your calories and every macro falls proportionally, including the two that should not.

Set the two that have real requirements in absolute terms, let the third flex, and the whole thing becomes stable across changes in calorie intake.

Why protein is set per kilogram, not per calorie

Protein requirement tracks how much body you have — specifically how much lean mass there is to maintain. It has essentially nothing to do with how many calories you are eating today.

That distinction produces a real failure when protein is set as a percentage. Consider a heavier person entering a deficit. Their calories go down, so a fixed percentage of those calories gives them fewer grams of protein — at precisely the moment protein matters most, because a calorie deficit is when the body is most likely to break down muscle for energy. The percentage approach reduces protein exactly when it should be increasing it.

Reasonable working figures are around 2.2 grams per kilogram of bodyweight while losing fat, 1.8 while trying to build muscle, and about 1.6 while maintaining. The number is highest when cutting for the reason above: in a deficit, protein is protective, and the goal is to lose fat rather than tissue.

For people carrying substantial excess weight, scaling from total bodyweight overshoots, because the requirement follows lean mass rather than fat mass. Using a target weight, or lean mass if you have a body fat estimate, gives a more sensible number than multiplying a very high bodyweight by 2.2.

Fat is a floor, not a target

Dietary fat gets treated as the variable to minimise, which inverts what it is. There is a genuine minimum below which things go wrong, and above that minimum the exact amount is largely a preference.

The floor is commonly put around 0.6 grams per kilogram of bodyweight. Below it, two problems appear. The fat-soluble vitamins — A, D, E and K — require dietary fat to be absorbed, so a very low fat intake impairs absorption regardless of how much of those vitamins you consume. And sex hormone production is fat-dependent, with the effects showing up as fatigue, poor recovery and, in women, menstrual disruption.

A practical target is around a quarter of total calories, and closer to 28 percent when not in a deficit. Set it as the higher of that percentage and the per-kilogram floor, so an aggressive cut cannot push it below the minimum by arithmetic alone.

Above the floor, higher fat and lower carbohydrate or the reverse is mostly a question of what makes you feel better and what you will adhere to. There is no strong evidence that the split matters for fat loss once protein and total calories are matched — which is a genuinely liberating finding, because it means the argument people spend the most energy on is the one that matters least.

Carbohydrate as the remainder

Once protein and fat are set, carbohydrate is simply the calories left over divided by four. It is the only macro with no established minimum requirement — the body can produce the glucose it needs from other sources — which is exactly why it is the right one to flex.

That does not make it unimportant. Carbohydrate is the most readily available fuel for hard training, and low-carbohydrate training tends to feel noticeably worse even when performance is only slightly affected. If sessions feel flat, carbohydrate is usually the first place to look, and taking most of the day's intake around training is the cheapest adjustment available.

It also has a signalling effect on adherence. Very low carbohydrate intakes are difficult to sustain socially, and a diet abandoned in week five loses to a slightly less optimal one continued through month six.

There is one point where the arithmetic breaks: if the calorie target is low enough and the protein target high enough, protein and essential fat can consume the entire budget and leave nothing for carbohydrate. That is not a macro problem, it is a signal that the deficit is too aggressive. The fix is to raise calories, not to cut protein.

Where the calorie target comes from

None of this works without a calorie number to divide up, and that number comes from two steps rather than one.

The first is basal metabolic rate — what the body uses at complete rest, driven mostly by size, age and sex. The second is a multiplier for activity, which converts that into total daily energy expenditure: roughly what you burn on an ordinary day. The multipliers are the weak link. People systematically overestimate their activity level, and choosing "very active" rather than "moderately active" can move the estimate by several hundred calories.

A deficit is then taken from that total. Something in the region of a fifth below maintenance is a common working figure, producing steady loss without the adherence problems and muscle loss that come with aggressive deficits.

Treat the whole calculation as a starting point rather than a measurement. Estimated expenditure carries real error for any individual, so the honest procedure is to set the number, hold it for two or three weeks, weigh yourself consistently, and adjust based on what actually happened. The scale is the measurement; the calculator is the hypothesis.

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