- How much protein should I eat in a day?
- Is the 0.8 grams per kilogram on the chart enough?
- Does the number change if I train, if I am over sixty, or if I am losing weight?
- Is more protein hard on my kidneys?
WHERE THE 0.8 COMES FROM
The official minimum for an adult, the figure on the government chart, is 0.8 grams of protein per kilogram of body weight per day. It comes from a meta-analysis of nitrogen balance studies published in 2003, which found that the median healthy adult stays in nitrogen balance at about 0.65 grams per kilogram, and set the recommendation two standard deviations higher so that almost everybody would be covered [1].
Read that again. It is the amount that prevents deficiency in 97.5 percent of healthy adults. It was never designed to be the amount that keeps a seventy-year-old’s legs strong or that protects a lifter’s gains in a cut. For a 70-kilogram (154-pound) person it works out to 56 grams a day. I treat it the way I treat 90 percent oxygen saturation on a pulse oximeter: below it, something is wrong; at it, you are not yet where you want to be. The researchers who do this for a living have said so in position papers for a decade. Treat 0.8 as the floor of the bucket, not the target.
THE WORKING RANGE, BY WHO YOU ARE
Here are the numbers, with where they come from, because the agreement between them is the most convincing thing about them.
If you exercise. The International Society of Sports Nutrition puts the range at 1.4 to 2.0 grams per kilogram per day for adults who train, and allows more for trained people in a calorie deficit [2]. A meta-analysis of 49 trials in which 1,863 people lifted weights with or without extra protein found that the benefit to muscle and strength plateaued at about 1.6 grams per kilogram per day, and that the benefit shrank with age [3]. That is the strongest-graded entry on our evidence chart: protein and muscle gain with resistance training.
If you are over sixty-five and do not train. The geriatric position papers put the range at 1.0 to 1.2 grams per kilogram per day for healthy older adults and 1.2 to 1.5 for those who are ill or malnourished, paired with exercise [4, 5]. The chart carries this as the protein guideline entry for adults 65+.
If you are losing weight on purpose. In diet-only weight loss, a meta-analysis of 24 trials found that higher-protein dieters kept about 0.4 kilograms more fat-free mass than standard-protein dieters [6], and the effect was largest when the higher protein was paired with resistance training [7]. That is the lean-mass preservation during caloric restriction entry, graded strong.
Different populations, different numbers, same message: well above 0.8. And notice how tight the agreement is. Sports scientists, geriatricians and the meta-analysts landed within a few tenths of a gram of each other from completely different directions. When that happens in science, you are looking at something real.
Key Points:
- 0.8 g/kg/day prevents deficiency in nearly everyone. It was never a muscle target [1].
- Adults who train: 1.4 to 2.0 g/kg/day, with the benefit plateauing near 1.6 [2, 3].
- Healthy adults over 65: 1.0 to 1.2 g/kg/day; 1.2 to 1.5 when ill or recovering, with exercise [4, 5].
- Anyone in a calorie deficit: the higher end of their range, because fast loss costs lean tissue [6, 7].
- For most of the people my book was written for, 1.2 to 1.6 g/kg/day is the working range.
THE DAILY NUMBER IS ONLY HALF THE RULE
A daily total can hide a bad pattern. Thirty grams at breakfast, nothing at lunch and ninety at dinner adds up to a respectable total and still leaves most of the day in muscle breakdown, because muscle protein synthesis responds meal by meal. Each meal has its own threshold: about 0.24 grams per kilogram in young adults and about 0.40 grams per kilogram in older adults, from the tracer dose-response work [8]. In plain food, that is 20 to 30 grams per meal when you are young and 30 to 40 when you are past sixty.
Three meals a day that each clear the per-meal threshold will, for most people, land the daily total inside the working range without any arithmetic. The person who clears the threshold at zero meals and makes it up with one enormous dinner is in a better position than the person who skips protein, but a worse one than the person who clears it three times. Distribution matters, and it matters more as you age. I have written the per-meal story in full at the protein-per-meal threshold.
One thing in your favour if you can only manage small meals: a smaller dose that does not clear the bar still contributes to the daily total. It is not wasted. It just does not trigger the full synthesis response on its own.
WHICH WEIGHT TO USE
Grams per kilogram of what? For most readers, actual body weight is fine. If you carry a lot of excess fat, your true weight will push the target high, because fat tissue does not need feeding the way muscle does. In that case use an adjusted or ideal body weight, the way the bariatric and geriatric guidelines do, and ask a dietitian to set it with you [9]. The arithmetic is simple either way, and I have worked it once so you can do your own: an 80-kilogram person on the over-60 range of 1.2 to 1.5 grams per kilogram needs 96 to 120 grams of protein a day. A 70-kilogram person who trains, at 1.6, needs 112.
THE AMMONIA CORRECTION
I owe you this section, because for years I told people that most of the protein they ate was “lost to ammonia,” and I quoted tables that said 55 percent of the protein in an egg and 85 percent of the protein in plants was never used as amino acids. Those tables came from a series of papers on one product, using a measure that, as far as I can tell today, nobody outside that group ever reproduced with a standard method. I was wrong about the size of that number, and I would rather tell you here than have you find out from your dietitian.
Here is what the standard methods say. When researchers measure how much of a protein’s amino acids are actually absorbed by the end of the small intestine, the answer for eggs, dairy, meat and fish is above ninety percent. The 2013 expert consultation convened by the Food and Agriculture Organization recommended scoring protein quality on exactly these digestibility measurements, amino acid by amino acid [10]. Under the new score, whey, milk and egg sit above 1.0, meaning they deliver every essential amino acid at or above the reference level; some plant proteins sit well below [11]. That is the real story of “plants are a worse protein source.” It is a story about lysine, methionine and leucine content and about digestibility in the eighties rather than the nineties. It is not a story about 85 percent going to waste.
What about the ammonia? Every amino acid you oxidize for fuel gives up its nitrogen as ammonia; the liver converts it to urea and the kidneys excrete it. This is the urea cycle, it runs in every healthy person after every meal, and in a healthy liver it keeps blood ammonia low across the whole range of normal diets [12]. When researchers deliberately pushed leucine intake in young men to find the ceiling, blood ammonia only climbed above normal past about 500 milligrams of leucine per kilogram per day, which is roughly 35 grams of leucine, or the leucine in well over 400 grams of protein [13]. Nobody eating food gets there. Your steak, your eggs, your yoghurt are working for you at better than ninety cents on the dollar.
THE KIDNEY QUESTION
This is a real grey area, so I will be careful, because I used to be careless about it, and because the careful answer is reassuring for most readers.
For healthy adults, a higher-protein diet does not harm the kidneys. A 2018 meta-analysis of 28 trials with 1,358 participants compared higher-protein diets with normal or lower ones and found no difference in the change in kidney filtration rate [14]. Healthy kidneys handle urea. That is what they are for.
But the rule has a hard exception. In people who already have reduced kidney function, higher protein intake has been linked to a faster decline [15], and the kidney guidelines recommend a lower, controlled protein intake for diagnosed chronic kidney disease, set by the clinician, not the gym [16]. So: healthy kidneys, eat to your target; damaged kidneys, your nephrologist writes the number and this page defers to them. If you are over sixty, diabetic, hypertensive, or have ever been told your kidney numbers were off, get a creatinine and eGFR before a sustained higher-protein plan. Not because protein is dangerous, but because the test tells you whether the ordinary rules apply to you.
VEGAN? FINE. HERE ARE THE THREE ADJUSTMENTS
I have done this one from the inside. I have been vegetarian and vegan, for health reasons rather than ethics, and I came back to being an omnivore, so I am not here to argue you out of your diet. I am here to make it work for your muscle, which takes three adjustments, and the trial evidence says that when you make them, it works.
- More total protein. Plant proteins are digested a little less completely and are often short in lysine, methionine, or the leucine that pulls the trigger [11, 17]. Eat more total protein and blend your sources so the gaps fill each other.
- Lean on the complete plant proteins. Soy and its relatives are complete and digest well; most single beans and grains do not, on their own [17].
- Mind the per-meal leucine. A vegan eating enough by the daily gram can still be under the leucine bar at every meal. A larger serving, a soy-based shake, or a leucine-aware blend clears it.
The one controlled trial that matched plant and animal eaters at 1.6 grams per kilogram found identical muscle and strength gains over twelve weeks of training [18]. The diet is not the limit. The amount and the quality are.
HOW TO FIND YOUR OWN NUMBER
This is the master assessment from my book. Everything else is a cross-check on it, and it costs nothing.
- Weigh yourself in the morning, in kilograms. If you think in pounds, divide by 2.2.
- Log everything you eat for three ordinary days, not three best-behaviour days, using any app or notebook that reports grams of protein. Add the three daily totals and divide by three.
- Divide that average by your body weight in kilograms. That is your grams per kilogram per day.
- Compare it to the working range for your situation: 1.2 to 1.6 for most people, 1.0 to 1.2 for a healthy older adult who is not yet losing ground, up to 2.0 and beyond for a trained person in a deficit [2, 3, 4]. If you are below your range, you have found your problem.
- Count the meals that clear the per-meal bar. Three is the target. Most people are at one.
Then re-assess in four weeks with a grip dynamometer and a kitchen chair: the European working group’s cut-points for concern are grip below 27 kilograms for men and 16 for women, and more than about 15 seconds for five chair stands [19]. The direction matters more than the single number. And one yellow light to carry everywhere: losing faster than about one percent of your body weight per week, for any reason, pulls disproportionately from lean tissue [20]. If that is happening on a drug or after surgery, it is a conversation with your prescriber, not a victory.
The Bottom Line. 0.8 is the floor. The working range for most adults is 1.2 to 1.6 grams per kilogram a day, higher if you train hard or are cutting, spread so that three meals each clear the per-meal bar. Healthy kidneys handle it; damaged kidneys get their number from a nephrologist. Measure it once with a three-day log and you will know more about your protein status than most people ever learn. Then get educated, ask questions, and advocate for yourself.