Dear readers,
In February 2025, more than twenty of the world’s leading protein researchers gathered at Indiana University with a single objective: to “pressure-test” what we think we know about dietary protein. The resulting paper, published this month in Critical Reviews in Food Science and Nutrition, runs nearly fifty pages and works through eleven of the most widely repeated claims about protein in human health.
I read it cover to cover. Then I read it again with my patient panel in mind — the women in their fifties trying to build muscle for the first time in their lives, the men on testosterone optimization who want every gram they eat to do real metabolic work, and the growing number of patients I see each week who are losing weight rapidly on GLP-1 receptor agonists and asking, quite reasonably, how to keep that weight loss from costing them their muscle.
Here is what the experts agreed on, what they pushed back against, and what it means for the way I counsel patients on protein.
The guidelines just caught up with the science
For decades, the Recommended Dietary Allowance for protein has been 0.8 grams per kilogram of body weight per day — a number set to prevent deficiency, not to optimize muscle, support healthy aging, or preserve lean mass during weight loss. It is, by design, a floor.
In January of this year, the federal government finally moved that floor. The 2025–2030 Dietary Guidelines for Americans raised the protein serving goal to 1.2 to 1.6 grams per kilogram of body weight per day — a meaningful revision that reflects what the protein research community had been arguing for years. For a 150-pound woman, that is the difference between roughly 55 grams of protein per day under the old recommendation and 82 to 109 grams under the new one.
One technical note worth understanding, because the terminology gets confusing: the formal RDA — the number set by the National Academies of Sciences through the Dietary Reference Intakes process — is still 0.8 g/kg/day on paper. The DRIs themselves have not been formally revised. What changed is the Dietary Guidelines for Americans, which is a separate federal document. The Kanter review I am drawing from still references the older 0.8 figure because that is the technical RDA, but the operative recommendation for most clinical purposes is now substantially higher.
Whichever number you use, the direction of travel is clear, and it matches what I have been telling my patients for years. The gap between just-getting-by and actually building the metabolic resilience that defines healthspan is real, and it is measured in grams of protein per day.
The per-meal number you should remember: 0.3 grams per kilogram
If there is one takeaway from this review that I want every patient to internalize, it is this: muscle protein synthesis is stimulated meal by meal, not over the course of a day, and there is a threshold below which a meal simply does not “turn on” the anabolic machinery.
That threshold, established through some of the most rigorous tracer-based research in the field, is about 0.3 grams of high-quality protein per kilogram of body weight per meal. For most of my patients, that translates to 25 to 35 grams of protein at each main eating occasion. A scoop of Greek yogurt with a tablespoon of nut butter on top is not enough. Three eggs and a piece of toast is closer. Six ounces of salmon, a chicken breast, or a properly built protein shake will get you there.
For women over sixty, the threshold appears to rise — they need closer to 30 grams, and some data suggest up to 40 grams post-exercise, to achieve the same anabolic response younger adults get from 20. Anabolic resistance is real, and the way we counter it is not with smaller, more frequent snacks; it is with substantial, protein-dense meals.
Quality is not a sustainability debate. It is a biochemistry conversation.
The review devotes considerable attention to protein quality, measured most rigorously by the Digestible Indispensable Amino Acid Score (DIAAS). Animal proteins generally score 90 to 95%. Plant proteins typically score 40 to 90%, with many common sources (beans, nuts, most grains) falling at the lower end of that range.
This is not an ideological claim. It is a measurement of how much of each essential amino acid actually makes it across the gut wall and into circulation where the body can use it. A study cited in the review found that you need to eat roughly 0.52 g/kg of a plant-based meat alternative to elicit the same muscle protein synthesis as 0.3 g/kg of beef. That is nearly twice as much food for the same biological effect.
I am not telling my patients to abandon plant proteins. The same review acknowledges that legumes, nuts, and seeds bring fiber, phytochemicals, and antioxidants that animal foods don’t. What I am telling them is that if your goal is to preserve or build muscle, especially in midlife and beyond, you cannot treat one ounce of chicken and a quarter cup of beans as nutritionally interchangeable, even though MyPlate’s “ounce equivalents” might suggest you can.
What this means for GLP-1 weight loss
This is the section of the review I have been waiting for someone to write.
Patients on GLP-1 receptor agonists are losing weight at rates we have never seen outside of bariatric surgery. The data suggest that for every kilogram lost during caloric restriction, roughly 20 to 25 percent of that loss in men, and 10 to 15 percent in women, comes from muscle and other lean tissue rather than fat. With aggressive GLP-1-induced weight loss, that percentage can climb higher, especially when appetite suppression leaves patients eating far less protein than they did at baseline.
The review is clear: higher protein intake during weight loss preserves lean mass. A diet providing roughly 1.45 g/kg/day during caloric restriction preserves significantly more lean mass than one at the RDA. But the most important nuance — and one I want every GLP-1 patient to understand — is that what matters is maintaining habitual protein intake in grams per kilogram, not simply increasing the percentage of calories from protein. When your total food intake drops by 30 to 40 percent, you have to deliberately, structurally rebuild your meals to be more protein-dense, because the default trajectory is a substantial drop in absolute grams.
Pair this with resistance training, which the review describes as having “no nonresponders” and “few if any contraindications,” and you have the most powerful body-recomposition strategy available outside a research setting. This is the protocol I build for every GLP-1 patient in my practice, and the science here is the reason why.
What didn’t hold up under scrutiny
Several beliefs you have probably heard repeated for years did not survive the experts’ review:
“High protein damages your kidneys.” Not in healthy people. The meta-analyses are clear. The transient rise in glomerular filtration rate that some studies show with higher protein intake reflects a normal response to higher solute load, not kidney injury. This is different in patients with established kidney disease, where individualized restriction may be appropriate, but for the otherwise healthy patient — including the otherwise healthy patient over sixty — higher protein is not nephrotoxic.
“High protein leaches calcium from your bones.” The review rates the evidence as “sufficient to rule out the viability of the proposition.” This is the strongest dismissal the panel issued for any claim in the entire paper. Yes, urinary calcium rises with higher protein intake. It rises because intestinal absorption rises in parallel. Net calcium balance is unchanged, and protein actually appears to support bone health, both through direct effects on the bone matrix and through its impact on muscle (the two tissues are now properly understood as a single musculoskeletal unit).
“Protein is the most satiating macronutrient.” The review is honest here in a way I appreciated: the experts couldn’t get to “yes” on this one. The effect, where it exists at all, is small and inconsistent, and human appetite is governed by far more than gut hormones and macronutrient ratios. If you are choosing higher protein because you believe it will single-handedly suppress your appetite, you may be disappointed. If you are choosing higher protein because it builds and preserves the tissue that drives your metabolic rate, you are on solid ground.
What we still don’t know
I want to be honest about the limitations the review surfaced, because I think this is where the science is most likely to evolve over the next decade.
We do not yet have good long-term human data on whether reducing specific amino acids — methionine, the branched-chain amino acids, isoleucine — can meaningfully extend healthspan the way it does in mice and flies. The animal data are striking. Isoleucine restriction extended male mouse lifespan by 33 percent in one study. But humans are not mice, we live in microbial environments mice don’t, and protein restriction strategies that look beautiful in a specific-pathogen-free vivarium may behave very differently in real life. I am watching this literature closely. I am not yet recommending amino-acid-restriction protocols to my patients.
We also do not have clean long-term data on whether protein intakes above two grams per kilogram per day, sustained over decades, alter cardiometabolic risk in any meaningful way. The short-term data are reassuring. The decades-long data simply do not exist yet.
What I want you to take from this
If you remember three things from this post, let them be these.
Aim for at least 1.2 grams of protein per kilogram of body weight per day — the new federal floor — and closer to 1.6 if you are actively training or trying to recompose your body. For most of my patients, this means 90 to 130 grams per day, not the 50 to 70 grams they were getting at baseline.
Hit roughly 30 grams of high-quality protein at each main meal. Skewing your protein toward dinner is the default American pattern and it is leaving anabolic potential on the table at breakfast and lunch.
Pair protein with resistance training. The two are synergistic in a way no other nutritional intervention I know of is. Protein without training builds less than you’d expect. Training without protein recovers less than it should. Together, they are the most reliable lever you have.
Protein is not a magic macronutrient. But it is the macronutrient most directly tied to the tissue that determines how well you will move, metabolize, and recover in the second half of your life. The science is now clear enough that we can speak with real confidence about how to use it.
The art is in how we put it on your plate.
To get started, call our office at 703-666-4144 or schedule a consultation with us.
Dr. Aleksandra Gajer
Founder, The Gajer Practice | Burke, Virginia
Board-Certified Physician | Functional & Performance Medicine
