Protein, macros and calories: how I set 40/30/30

Short version: I set 40% of your daily calories from protein, then split the rest roughly 30% carbs and 30% fat. Then I turn it into grams. Step one is knowing your calories, so I'll show you how I'd estimate them.

This is my approach, N=1, strongly biased and not medical advice.

Why your last diet probably failed

You've heard "eat less, move more" from everyone, including that one cousin. You tried the salad that was mostly leaves and hope. You were hungry by 3 p.m., ate the leftover pasta standing at the fridge, and decided you had no willpower.

Often the plan was the problem: vague portions, too little protein, no numbers. "Eat clean" isn't a plan. It's a mood.

Why 40/30/30

• Protein is the priority. I put it first at 40% because protein is what helps you feel full and what you want to protect when you're eating less.
• It's easy to remember. 40, 30, 30. You can do it on a napkin.
• It becomes grams. Percentages don't fit in a lunch box, but grams do.

Step 1: estimate your daily calories

This is a starting estimate, not a verdict. I use the Mifflin-St Jeor equation, widely published and one of the best-validated general equations, then multiply by activity.

Resting calories (BMR)

• Women: 10 x weight (kg) + 6.25 x height (cm) - 5 x age - 161
• Men: 10 x weight (kg) + 6.25 x height (cm) - 5 x age + 5

Pounds to kg: divide by 2.2. Inches to cm: multiply by 2.54.

Optional: if you happen to know your body-fat percentage, the Katch-McArdle formula can be more accurate for lean or very muscular people. Lean mass (kg) = weight (kg) x (1 - body fat as a decimal). Then BMR = 370 + 21.6 x lean mass (kg). Body-fat readings from scales and calipers are rough, so if you don't trust your number, stick with Mifflin-St Jeor. Either way, it's still a starting estimate.

Multiply by your activity

• Mostly sitting: x 1.2
• Light (1 to 3 workouts a week): x 1.375
• Moderate (3 to 5 workouts a week): x 1.55
• Very active: x 1.725
• Very high (athlete, or a physical job plus training): x 1.9

If you're between two levels, pick the lower one.

Subtract for fat loss

A common rule of thumb is that a loss of about 0.5 lb a week is roughly 250 fewer calories a day. Keep the deficit modest. I'd rather you lose slowly than crash and quit.

Safety limits: don't aim for more than about 2 lb (0.9 kg) a week, keep your deficit to no more than about 25% of your maintenance calories, and don't go below a floor of about 1,200 calories a day (women) or 1,500 (men). Whichever limit you hit first is the one that counts, and for most people the 25% rule bites first.

Building muscle instead?

If your goal is to gain muscle, add about 200 calories a day to your maintenance number instead of subtracting.

A worked example (hypothetical numbers)

Take a made-up 45-year-old woman, 70 kg (154 lb), 165 cm (65 in), who lifts about 3 times a week.

• BMR: 10 x 70 + 6.25 x 165 - 5 x 45 - 161 = about 1,345.
• Activity: x 1.375 = about 1,850 calories to maintain.
• Aiming for 0.5 lb a week: minus 250 = about 1,600 calories a day.

Now the split:

• Protein 40%: 640 calories / 4 = 160 g.
• Carbs 30%: 480 calories / 4 = 120 g.
• Fat 30%: 480 calories / 9 = about 53 g.

That's a made-up person, not you. Run your own numbers, round to the nearest 10 calories (it's an estimate, so don't chase decimals), eat that way for 2 weeks, then adjust from your results.

The Bull app does this step for you with its own formula, based on your weight, height, activity and your goal. In the app, I review each member's targets before they see them, so the figure there can differ slightly from this blog calculator after my review.

What a plan should look like

Here's what I require from a plan, and what you should demand from any plan:

• Specific gram measurements. 180 g of something, not "a bowl".
• A substitute for every item. No chicken today? Here's the swap.
• Macros per food and per meal, so you can see where the protein comes from.

Food first, powder second. A shake is a convenience, not a moral choice.

When progress stalls

Don't cut calories, and definitely don't halve them. I cycle the same weekly totals: more carbs on training days (about 150 g) and fewer on rest days (about 80 g). Track the 7-day average and your measurements, as I explain in why the scale lies.

Low-fat day? Fine in a fat-loss phase, as long as you hit protein. I only flag it if low fat lasts a week or more.

Who should check first

If you have kidney disease, are pregnant, have a medical condition affecting how you eat, or follow a medically supervised diet, don't take a number from a trainer's blog. Talk to your doctor or a registered dietitian.

Next steps

If doing this math every month sounds tiring, that's what the Bull app is for. It opens early November. See the app. For lifting that matches the food, read strength training after 40. More notes are in the book.

Quick answers (FAQ)

What does 40/30/30 mean?

In my approach, 40% of your daily calories come from protein, 30% from carbs and 30% from fat. You turn those percentages into grams, since protein and carbs are about 4 calories per gram and fat is about 9.

Is the calorie formula exact?

No. It is a starting estimate. Check your results after 2 weeks using your 7-day average weight and your measurements, then adjust.

What are the safety limits for losing fat?

In my approach: no more than about 2 lb (0.9 kg) a week, a deficit of no more than about 25% of your maintenance calories, and a floor of about 1,200 calories a day for women or 1,500 for men. If you have a medical condition, check with your doctor first.

What if I know my body-fat percentage?

Optional: the Katch-McArdle formula can be more accurate for lean or very muscular people. BMR = 370 + 21.6 x lean mass in kg, where lean mass is your weight times (1 minus your body-fat percentage as a decimal). Then multiply by your activity level as usual. If you don't trust your body-fat number, stay with Mifflin-St Jeor.

Do I need protein shakes?

No. Food comes first. A shake is a convenience, not a rule.

Who should talk to a professional first?

Anyone with kidney disease, anyone who is pregnant, and anyone with a medical condition or on a supervised diet. 40% protein is a high-protein plan, so ask your doctor or a dietitian.