How much protein do you actually need per day?

Ask ten people how much protein you should eat in a day and you'll get ten numbers between 40g and 250g. The fitness internet says "1g per pound of bodyweight." Government guidelines say half that. Most bodybuilders eat twice that again.

The real number is in there somewhere, but it depends on four things — your weight, your training, your goal, and how old you are. Here's the honest math.

The quick answer

For most adults who train a little, 1.6 grams per kilogram of bodyweight is the evidence-backed target. For a 75 kg person, that's 120g of protein a day. It works for muscle maintenance, it works for weight loss, and it's achievable without living on chicken breast.

Where "1g per pound" came from (and why it's almost right)

Gym-floor wisdom says "1g of protein per pound of bodyweight." For a 75 kg (165 lb) person, that's 165g — very close to the 1.6 g/kg number (120g).

It's not wrong, exactly. It's the top end of the useful range for people actively gaining muscle. For everyone else — deficit dieters, recreational gym-goers, desk workers — it's 30–40% more protein than you actually need.

The problem is the number got internalized as a floor, not a ceiling. At 165g protein, a 75 kg person is eating 660 kcal of protein alone, which is a huge chunk of the day in a deficit. Most of that protein above ~1.6 g/kg is just expensive urine.

The four multipliers

1. Sedentary vs active

Government RDAs (0.8 g/kg) were set to prevent deficiency in sedentary adults. They're not a target for optimal body composition. If you lift, walk 8k+ steps, or play a weekly sport, 0.8 g/kg is a floor — not a goal.

2. Training status

Protein synthesis spikes after resistance training, and it stays elevated for ~24 hours. Lifters need more protein than runners, who need more than walkers. The jumps:

• No training: 0.8–1.0 g/kg
• Endurance training (running, cycling 3–5×/week): 1.2–1.4 g/kg
• Resistance training (lifting 3–5×/week): 1.6 g/kg
• Heavy training + aggressive hypertrophy goals: 1.8–2.2 g/kg

3. Calorie deficit protects muscle

This is the under-appreciated one. In a deficit, your body can burn fat or muscle for fuel. High protein intake tilts that ratio — more fat, less muscle. Research is clear: during weight loss, protein targets should be on the higher end of your normal range, not the lower.

For a deficit dieter who's also training, 1.6–2.0 g/kg is the evidence-backed window. Below 1.2 g/kg in a deficit, you will lose measurable muscle no matter how clean the rest is. (This is one of the reasons people stall on a deficit and end up heavier long-term — they ate at 1,200 kcal with 60g protein, lost muscle, tanked their TDEE, rebounded.)

4. Age

After roughly 55, your body becomes less responsive to protein — a phenomenon called anabolic resistance. Older adults need more protein per kg to trigger the same muscle-protein-synthesis response:

• 18–55: 1.6 g/kg is a reasonable target for active adults
• 55–70: bump to 1.8–2.0 g/kg, especially if muscle-preserving is the goal
• 70+: the highest range, often 2.0+ g/kg alongside regular resistance training

Older adults who hit these targets hold muscle mass dramatically better than peers who don't. It's one of the highest-leverage interventions for healthy aging.

Plant-based: the same math, with a catch

Plant proteins are "incomplete" individually — they don't contain all nine essential amino acids in optimal ratios the way meat, dairy and eggs do. That's not a deal-breaker; it just means the total number needs to be ~10% higher to hit the same effective protein target.

The "varied sources" part matters. Rice + beans together is complete. Soy, quinoa and buckwheat are complete on their own. Plant-based eaters who hit 1.8 g/kg with a mix of sources get the same muscle outcomes as omnivores at 1.6 g/kg — this is well-replicated in the literature now.

How to actually hit the number

For most people targeting ~120g/day, the math breaks cleanly into 3–4 meals of 30–40g each.

A realistic day:

• Breakfast: 30g — Greek yogurt + eggs (see seven two-minute swaps — breakfast is where most people leak protein)
• Lunch: 40g — 150g chicken breast or equivalent (full chicken breast math if that's your staple)
• Snack: 15g — cottage cheese, tuna, or a protein bar
• Dinner: 35g — salmon, lean beef, tofu, or chicken again

= 120g without much creativity.

What happens if you over-eat protein?

Almost nothing bad, for most healthy adults. Excess protein is either oxidized for energy or converted to glucose. You don't "store" it as muscle unless there's a training stimulus requiring it.

The real downside of eating 250g protein/day isn't health — it's opportunity cost. Every gram of protein above your usable ceiling is crowding out either fat (needed for hormones) or carbs (needed for training). In a deficit especially, this matters. 250g protein = 1,000 kcal of protein alone, which might be half your daily budget. (Which of the two remaining macros to cut further — carbs vs fat in a deficit — gets its own post.)

Exception: if you have kidney disease, your doctor's protein target is the one that applies, not this one.

The five-line summary

1. 1.6 g/kg is the target for most active adults
2. 1.8–2.0 g/kg during a calorie cut, to protect muscle
3. 30–40g per meal, spread across 3–4 meals
4. Older adults need more, not less
5. 1g per pound is only right for hard-training hypertrophy athletes

Most people are under-eating protein, not over-eating it. If you log honestly for a week and land at 80g as a 75 kg active adult, you've found the lever. Add 30g to breakfast and a scoop of cottage cheese with dinner — you're at 120g without changing anything else.

Pairs well with: how much of a calorie deficit to run, which uses this protein number as the first constraint, not the last.