Let’s be honest. Most people treating their gym bag like a laboratory are still guessing. You see them hovering over a digital scale, weighing a chicken breast like it’s a precious gemstone, all because some guy on TikTok said you need two grams of protein for every pound you weigh. That’s a lot of chicken. It’s also, for most of us, total overkill. If you’ve been stressing about your protein per kg of body weight, it’s time to breathe. We need to talk about the actual science, not the locker room myths that have been recycled since the 1970s.
The truth is nuanced.
The "Standard" recommendation you see on every government website—the Recommended Dietary Allowance (RDA)—is roughly $0.8g$ of protein per kilogram of body mass. For a 70kg person, that’s about 56 grams. That is tiny. It’s basically the bare minimum to keep your hair from falling out and your skin from sagging. It’s the "don't get sick" number, not the "look great in a t-shirt" number. If you are even remotely active, that RDA number is a joke.
The Sweet Spot for Muscle and Longevity
The real conversation starts when we look at people who actually move. Dr. Stuart Phillips, a researcher at McMaster University who has spent decades poking muscles with needles, has shown consistently that the RDA is insufficient for optimal health. If you’re lifting weights or even just hitting a demanding yoga class three times a week, you’re looking at a different scale.
Most meta-analyses, including the massive one published in the British Journal of Sports Medicine that reviewed 49 studies, suggest that for muscle gain, the "ceiling" is around $1.6g$ of protein per kg of body weight.
Think about that.
If you weigh 80kg (about 176 lbs), your target is roughly 128 grams of protein. That’s a far cry from the "2 grams per pound" (which would be $4.4g/kg$) that old-school bodybuilders swear by. Beyond $1.6g/kg$, the "returns" on that extra steak start to drop off a cliff. Your body doesn't just keep building more muscle because you ate more protein; it just starts burning that expensive protein for energy or, honestly, you just poop it out.
Why "Total Weight" is a Deceptive Metric
Here is where the math gets messy. If you are carrying a significant amount of body fat, basing your protein intake on your total weight is a mistake. Fat tissue isn’t metabolically active in the same way muscle is. It doesn't "demand" protein.
If someone weighs 120kg but has a high body fat percentage, eating $1.6g/kg$ would mean consuming nearly 200 grams of protein. That’s a massive amount of food that might be unnecessary. In these cases, experts like Dr. Eric Helms often suggest calculating protein based on Lean Body Mass (LBM) or your "goal" weight.
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It's simpler. It's more sustainable. It saves you money on whey powder.
The Aging Factor
We also have to talk about getting older. Sarcopenia is the fancy medical term for losing muscle as you age, and it’s a silent killer. Once you hit 50, your body becomes "anabolically resistant." Basically, your muscles become "deaf" to the signal that protein sends.
Because of this, older adults actually need more protein per kg of body weight than a 25-year-old sedentary office worker. Research published in The Journal of Post-Acute and Long-Term Care Medicine (JAMDA) suggests that seniors should aim for at least $1.2g$ to $1.5g/kg$ just to maintain the muscle they already have. If you have a parent who is mostly eating toast and tea, they are losing the very tissue that keeps them from falling and breaking a hip. It’s a serious issue that rarely gets enough play in mainstream health circles.
What Does This Actually Look Like on a Plate?
Forget the spreadsheets for a second. Let's look at real food.
If you are a 75kg woman who hits the gym four days a week, your target is likely around 120g of protein.
- A Greek yogurt for breakfast (15-20g).
- A chicken breast or a big serving of lentils at lunch (30-40g).
- A protein shake after the gym (25g).
- A piece of salmon for dinner (30g).
Boom. You're there.
It’s not about eating a whole cow. It’s about distribution. Research into "protein pacing" suggests that our bodies can only "process" so much muscle protein synthesis at once. This is debated, but many experts suggest aiming for 0.4g to 0.5g of protein per kg of body weight per meal. For our 75kg athlete, that’s about 30-37 grams per meal. Shoving all your protein into one giant 100g steak at dinner might not be as effective as spreading it out, though the "total daily intake" is still the most important factor by a long shot.
Common Myths That Just Won't Die
- "Your kidneys will explode." Unless you have pre-existing kidney disease, high protein diets have been shown to be perfectly safe in healthy individuals. A study by Dr. Jose Antonio even pushed protein as high as $3.4g/kg$—which is a ridiculous amount of food—and found no adverse effects on kidney or liver function after a year.
- "Plant protein doesn't count." It does. You just might need a little more of it because some plant sources are slightly less "bioavailable" or are missing certain amino acids like leucine. If you're vegan, maybe aim for the higher end of the $1.6g/kg$ range to account for that.
- "You need protein within 30 minutes of a workout." The "anabolic window" is more like an "anabolic garage door." It stays open for hours. As long as you get your total protein per kg of body weight for the day, you’re fine.
Practical Steps to Find Your Number
Don't just pick a number out of a hat. Use this hierarchy to figure out your needs:
- Calculate your weight in kg. (Weight in lbs divided by 2.2).
- Assess your activity. Are you sitting all day? $1.0g - 1.2g$ is fine. Are you lifting heavy or training for a marathon? You need $1.6g - 2.0g$.
- Adjust for body composition. If you have a lot of weight to lose, use your "ideal" or "goal" weight for the calculation instead of your current weight.
- Prioritize whole sources. Supplements are great, but whole foods like eggs, lean meats, beans, and fermented dairy come with micronutrients that shakes lack.
- Track for three days. You don't need to track forever. Just do it long enough to realize that you're probably eating way less protein than you thought. Most people are shocked to find they're only hitting 50 or 60 grams a day.
Getting your protein per kg of body weight right isn't about perfection. It’s about moving the needle from "surviving" to "thriving." Start by adding one high-protein element to the meal where you usually skip it—usually breakfast. Small shifts in these numbers lead to massive shifts in how you feel, how you recover, and how you age.
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Focus on the $1.2g$ to $1.6g$ range as your baseline. If you're hitting that consistently, you're already ahead of 90% of the population. No scale-obsessing required.