The number most people know — 0.8 grams of protein per kilogram of bodyweight — is the RDA, and it gets treated like a target. It isn't one. It's a floor, established mostly through nitrogen balance studies designed to find the minimum intake that prevents a sedentary adult from slowly losing muscle mass. It was never meant to represent an optimal intake for someone who lifts weights, plays a sport, or is trying to change their body composition. Using it as a goal is like using the speed limit for reversing out of your driveway as your goal for how fast to drive on the highway.
What the Research Actually Supports
For people doing regular resistance training, the research consistently lands in a higher range: roughly 1.6 to 2.2 grams per kilogram of bodyweight per day for maximizing muscle protein synthesis. Meta-analyses pooling dozens of trials find that intake above that range doesn't produce meaningfully better results for most people — more isn't harmful, it's just not doing much extra work once you're already in that zone.
It's Not Just About Muscle
Protein also has the highest thermic effect of any macronutrient — your body burns more calories digesting and processing it than it does for carbs or fat — and it's consistently the most satiating macro in appetite research. Higher-protein diets in controlled trials show better appetite regulation and, importantly, better preservation of lean mass during a calorie deficit, which is the difference between losing fat and just losing weight.
This matters even more for older adults. Age-related muscle loss, or sarcopenia, is a real and significant driver of frailty and loss of independence, and the RDA is especially inadequate for this group. Research on healthy older adults generally supports intakes closer to 1.2g/kg or higher to help counter it.
The Kidney Myth
The concern that high protein intake damages your kidneys traces back to studies on people who already had existing kidney disease, where reducing protein intake is a legitimate part of clinical management. That finding does not transfer to healthy people. Multiple studies looking at higher protein intakes in healthy adults with normal kidney function show no adverse effect on kidney markers over time. If you have diagnosed kidney disease, this doesn't apply to you — talk to your doctor about your specific numbers. If you don't, your kidneys are built to handle the workload.
How to Actually Hit Your Number
Total daily intake matters most, but distribution helps. Aim for roughly 25–40g of protein per meal, spread across three to four meals — that range comfortably clears the "leucine threshold" (about 2.5–3g of the amino acid leucine) that appears to maximize the muscle-building signal per meal, rather than trying to cram it all into one sitting.
The RDA tells you the minimum to avoid getting sick. It was never a performance or body-composition target. Most people who think they're "getting enough protein" are hitting the floor, not the range that actually helps — and the fix isn't complicated, it's just eating more of it, consistently, at every meal.