What Is Proteinmaxxing — and Should You Actually Do It?

The starting point for the trend is a fair criticism: the official protein Recommended Dietary Allowance (RDA) of 0.8 g per kilogram of body weight per day is not an optimal-performance target. It is the amount estimated to prevent deficiency in a sedentary, healthy adult — a floor, not a ceiling. It was never designed with muscle-building, aging-related muscle loss, or medication-driven rapid weight loss in mind.

Social media has run with that gap and, as usual, overcorrected — turning a legitimate “the RDA is a minimum” observation into a competitive sport of eating as much protein as physically possible. The evidence below sits in between: there are real, specific reasons certain people should eat more than the RDA, with real numbers attached — and there is a point past which more protein has no demonstrated extra benefit.

This is the strongest and most specific case for higher protein of the three. Aging brings measurable changes to how the body handles protein: older muscle becomes less responsive to a given dose of amino acids (a phenomenon researchers call “anabolic resistance”), and more of an ingested protein dose gets extracted and used by the gut and liver before it ever reaches muscle.¹ Combined with the natural, gradual loss of muscle mass and strength with age (sarcopenia), the practical effect is that older adults need more protein than younger adults to achieve the same muscle-preserving effect — not less, as the shrinking-appetite stereotype of aging might suggest.

The PROT-AGE Study Group — an international panel convened by the European Union Geriatric Medicine Society — reviewed the evidence and published specific targets for adults over 65:¹

• General older adults: at least 1.0–1.2 g/kg/day to maintain and regain lean body mass and function — noticeably above the standard 0.8 g/kg RDA.
• Active or exercising older adults: 1.2 g/kg/day or more.
• Older adults with acute or chronic illness (including most people managing sarcopenia): 1.2–1.5 g/kg/day, because inflammatory and catabolic disease processes raise protein needs further.
• Exception: older adults with severe kidney disease (estimated GFR below 30 mL/min/1.73m²) who are not on dialysis are specifically advised to limit protein intake — this population should not follow the general recommendation without medical guidance.

For a 70 kg (154 lb) older adult, that is a practical range of roughly 70–105 g of protein a day depending on activity and health status — often 30–50% more than what a standard low-protein diet or a shrinking appetite tends to deliver.

This is where “proteinmaxxing” intersects with one of the most-discussed drug classes in medicine right now: GLP-1 receptor agonists such as semaglutide (Ozempic, Wegovy) and the dual GIP/GLP-1 agonist tirzepatide (Mounjaro, Zepbound). These drugs work partly by sharply reducing appetite — which is exactly the problem for protein intake. Total food intake drops fast, and protein intake tends to drop along with it, right at the moment when preserving muscle matters most.

A 2024 systematic review of six clinical trials covering 1,541 overweight or obese adults on semaglutide found that most of the weight lost was fat mass — but lean mass reductions ranged from close to 0% up to roughly 40% of total weight lost, and the reductions were more pronounced in the largest trials. The ratio of lean mass to total body mass generally still improved, but the absolute muscle loss in some trials was substantial enough that the review’s authors flagged it as a genuine concern.² A separate 2025 opinion paper reached a similarly unresolved conclusion: findings across studies are inconsistent, some show meaningful lean-mass decline and others do not, and the authors called for more research given how quickly semaglutide use is expanding.³

For tirzepatide, the picture is illustrated well by a detailed case report: a 68-year-old man lost 28.7 lb on tirzepatide, and serial body-composition scans showed the loss was proportional — about 15% reduction in both total body weight and skeletal muscle mass, meaning muscle loss made up 34% of the total weight lost.⁴ That is one patient, not a population average, but it demonstrates the mechanism plainly: without a specific countermeasure, weight lost on these drugs is not all fat.

The countermeasure is the same one that works for any diet-induced weight loss: adequate protein plus resistance training. Clinical guidance for people on GLP-1 therapy commonly points to a similar range as the PROT-AGE recommendations above — broadly 1.2 g/kg/day or higher, distributed across meals so appetite suppression doesn’t concentrate the shortfall into one meal you can no longer finish — alongside resistance exercise to give the muscle a reason to be kept.

This is the oldest and most-studied of the three cases, and it is where the “20 grams and you’re done” internet rule of thumb actually comes from — along with why it is now considered oversimplified.

The number originates from a 2009 study that had young men perform resistance exercise, then drink 0, 5, 10, 20, or 40 g of egg protein. Muscle protein synthesis rose with the dose and plateaued at 20 g; the 40 g dose stimulated muscle protein synthesis no further and simply increased amino acid oxidation (the excess being burned for energy rather than built into tissue).⁵

A 2018 review revisited that finding and added an important nuance: the 20–25 g ceiling applies specifically to a fast-digesting, isolated protein taken alone. Slower-digesting proteins, or protein eaten as part of a mixed meal with fat and carbohydrate, absorb more gradually — which may let the body put more of a larger dose to use rather than oxidizing the surplus. Based on the full body of evidence, the review’s practical recommendation is to aim for roughly 0.4 g of protein per kilogram of body weight per meal, spread across at least four meals a day — which works out to a daily total in the neighbourhood of 1.6 g/kg, rather than trying to hit one enormous post-workout dose.⁶

Does the extra protein actually translate into more muscle and strength? A 2018 meta-analysis and meta-regression pooling 49 randomized trials and 1,863 participants found that, yes, protein supplementation on top of a resistance-training program produced small but statistically real improvements over resistance training alone: about +2.5 kg on one-rep-max strength, +0.3 kg of fat-free mass, and measurable increases in muscle fibre cross-sectional area.⁷ Real, but modest on average — and the benefit depends heavily on how much protein a person was already eating and how hard they are training. Someone already eating 1.6 g/kg who adds more protein without changing their training is unlikely to see much of that effect at all.

Does high protein damage healthy kidneys? This is the most persistent worry, and the evidence in people with normal kidney function does not support it. A 2018 systematic review of 26 studies in healthy adults found that most randomized trials showed higher glomerular filtration rate (GFR) with higher protein intake — but all of those rates remained within the normal range for healthy kidney function. The review also found little to no effect on blood markers of kidney health, and no adverse effect on blood pressure.⁸

Two honest caveats belong here. First, most of the included studies were short — under six months — and the review authors rated overall study quality as moderate to high risk of bias, so this is reassuring evidence for healthy kidneys over the short-to-medium term, not lifetime proof. Second, this evidence applies specifically to people with normal kidney function. It is not a green light for anyone with existing kidney disease — who should follow individual medical guidance, echoing the same exception PROT-AGE makes for older adults with severe kidney disease above.

Powder vs. whole food. Protein powder is a convenient way to hit a per-meal target, not an inherently superior one. Whole-food protein sources — fish, eggs, dairy, legumes, poultry — bring along nutrients a plain protein isolate does not: iron, B12, calcium, fibre (from legumes), and in the case of fatty fish, the omega-3s covered in our wild vs. farmed salmon guide. Powder is a reasonable tool for closing a gap; it is not a reason to skip whole-food protein sources entirely.