Protein in a deficit: how many grams per kilo to keep muscle

The calories are down, the scale is moving, and yet you look softer than you did a month ago. The weight you used to press for six now feels heavy at four. That is rarely a slow metabolism. In a deficit the body burns both fat and muscle, and protein intake is one of the two or three things that decide how that loss gets split.

The answer to the question in the title is a range: 1.6 to 2.4 grams of protein per kilo of body weight per day. Where you land inside it depends on how much fat you carry, how deep the deficit is, and how seriously you lift. The rest of this is about picking your number and actually eating it.

Step 1: treat 1.6–2.4 g/kg as the frame

Below roughly 1.6 g/kg the evidence that protein protects muscle in a deficit gets thin, and that is where strength and arm size tend to go together. Above 2.4 g/kg the extra benefit is small and hard to measure for most people. Research mostly points the same way: the gap between 1.2 and 1.6 g/kg shows up clearly, the gap between 2.0 and 2.8 g/kg barely does.

In practice, a 70 kg person is aiming at 112 to 168 g a day. An 85 kg person, 136 to 204 g. If this is the first time you have counted anything, start at the bottom of the range and hold it for six weeks rather than chasing the top and quitting by Wednesday.

Step 2: carrying a lot of fat? Use your goal weight

The per-kilo formula has one hole in it: fat tissue does not ask for protein. Multiply 120 kg by 2.2 and you get 264 g a day, which is both unnecessary and more food than most people can face without the whole thing turning into a chore.

Use a realistic goal weight instead. Someone at 120 kg heading for around 90 kg needs roughly 145–180 g a day, and that is plenty to protect muscle. The same correction works the other way: a smaller person at 55 kg multiplies by 1.8 and gets 100 g, not "about 150, because that's the number everyone writes".

Step 3: a deeper cut and less body fat push you upwards

Two situations call for more protein. The first is an aggressive deficit — the less energy coming in, the more willing the body is to burn muscle for fuel. The second is being already lean: with few reserves on board, the body reaches for muscle sooner, so someone with visible definition needs more protein than someone just starting out.

So check how deep the deficit actually is before you touch protein at all — the maths is simpler than it looks. If you are losing more than 1 per cent of body weight a week, the problem is speed, not protein. A sensible zone is 0.5 to 1 per cent a week, paired with the upper half of the protein range.

Step 4: without strength training there is nothing to protect

Protein is the material, training is the reason. If you are not lifting, nothing is telling the body to hang on to muscle, and 2.4 g/kg will not rescue that. It is the most common reason people lose their shape in a deficit while eating perfectly well.

The working minimum: two to four strength sessions a week and five to ten hard sets per muscle group per week, taken to within two or three reps of failure. The critical part is that the loads stay close to what you are used to. In a deficit you cut volume, not weight on the bar. When fatigue arrives, drop the third back exercise, not the kilos.

Step 5: spread it over three to five meals of 30–45 g

The daily total does most of the work; distribution is the fine tuning. Still worth doing: around 0.3 to 0.4 g per kilo of body weight per meal, three to five times a day, which lands most people at 25 to 45 g a sitting.

Breakfast is nearly always the gap. Coffee and something sweet gets you five grams, then you try to claw back 90 g across two evening meals and fall short. Add eggs, yoghurt or cottage cheese to the morning and the daily target moves 20 to 30 g on its own.

What 160 g of protein looks like across a day

• 150 g cooked chicken breast — around 45 g
• 200 g Greek yoghurt — 18 to 20 g
• three large eggs — around 18 g
• 100 g drained tinned tuna — around 25 g
• 150 g cottage cheese — around 17 g
• one scoop of protein powder (30 g) — 22 to 25 g
• 200 g cooked lentils — around 18 g

If you do not eat meat the target is identical, the route is just longer: combine dairy, eggs, pulses, tofu and soy, and plan a protein source in every meal rather than only at dinner. Plant sources bring more carbohydrate and fibre with them, so you will feel full sooner — useful in a deficit, awkward when you are chasing a number.

How to tell it is working

Give it three or four weeks, then check three things. The scale: the weekly average is dropping 0.5 to 1 per cent of body weight. Strength: your main lifts are within five to ten per cent of where they started. Waist: the tape is moving even though the reps are not.

If the scale falls while strength collapses, the deficit is too big or protein is too low. If nothing at all is shifting for weeks, run through the short checklist of what to look at before you add another rule.

Common mistakes

• Guessing portions. Raw and cooked meat do not weigh the same, and "a bit of cheese" varies by a factor of two. People underestimate portions in fairly predictable ways; two weeks with a kitchen scale fixes it permanently.
• Protein on weekdays only. Five days at 170 g and two at 60 g averages out neatly on paper, but the weekend is usually where the deficit disappears too.
• Running it all through shakes. Powder, milk and ready-made drinks are easy protein and equally easy calories that never register as a meal. Liquid calories add up faster than most people expect.
• Cutting too hard. On 1,200 kcal and a half-hour walk, protein is a patch on a hole it cannot cover.
• Swapping lifting for cardio. More time on the treadmill does not replace squats and rows; it is the quickest way to lose exactly what you are trying to keep.
• Counting bread and rice as protein. A slice of bread carries three or four grams. It adds up, but it does not build the day.

When to see a doctor

In people with healthy kidneys, a high protein intake is not a problem — but the advice changes once there is a diagnosis. Speak to a doctor before increasing protein if you have kidney disease or reduced kidney function, liver disease, diabetes, or if you are pregnant or breastfeeding.

Get checked too if you are losing weight faster than planned without a clear reason, if you feel dizzy, if periods stop, or if managing food starts taking up more room in your head than it should. Those are not things to solve by recalculating macros.

Common questions

Does a lot of protein damage the kidneys?

In people with healthy kidneys, the evidence does not show harm even at intakes above 2 g/kg sustained over long periods. With existing kidney disease it is a different conversation, and one for a doctor rather than an article.

Do I need protein powder?

You do not need it, but it helps. Powder is a tool for the days when you are 25 g short at bedtime, not the foundation of a diet. If you hit your number with food, you are missing nothing.

Does protein from pulses and grains count?

It counts — everything goes into the daily total. Plant sources have a weaker amino acid profile, so mix them and aim nearer the top of the range if they are your main source.

What if I simply cannot eat that much?

Then aim for 1.6 g/kg instead of 2.2 and add one protein meal that needs no cooking: yoghurt, cottage cheese, hard-boiled eggs. A consistent 1.6 g/kg beats an occasional 2.2 g/kg every time.

The short version

• Target 1.6 to 2.4 g of protein per kilo per day.
• Carrying a lot of fat? Base the sum on your goal weight, not today's.
• A deeper deficit and a lower body fat level mean the upper half of the range.
• Lift two to four times a week, and keep the loads where they were.
• Split it into three to five meals of 25 to 45 g, starting at breakfast.
• Check at four weeks: 0.5 to 1 per cent lost per week with strength intact means the plan is working.