Protein after 40: how much, when and from which foods.

Coffee and a croissant on the way in. At half twelve, a pasta salad at your desk between two meetings. At seven, finally, a steak and salad. It looks like a balanced day. Your muscles got one meal.

After 40 you lose a little muscle every year, quietly. And in the people I work with, I nearly always see the same mistake: not much protein, and nearly all of it at dinner.

Add up your day

Think back over yesterday's meals. Which ones had meat, fish, eggs, dairy or pulses?

• Breakfast. Coffee and a croissant. Next to nothing. And it follows the night, when the amino acids in your blood, the building blocks of protein, have dropped.
• Lunch. Pasta or a sandwich. Pasta has about 10 grams of protein per 100. It counts, but it's not enough.
• Dinner. This is where nearly all the day's protein turns up.
• The signs. You recover slowly after training, you're low on energy, you're ill more often.

Why you need more with age

Muscle is a building site that never closes. After a meal with protein, your body builds. In the hours without, it dismantles. What matters is the balance at the end of the day.

Your muscles go hard of hearing. With age the same meal sends a weaker signal, and it takes a bigger dose, in one go, to get the site going. Below that threshold you eat, but nothing gets built. That's why protein does more spread across meals than piled into dinner.

Muscle is last in the queue. Your body uses protein for enzymes, hormones and immune defences first. Muscle comes after. If little comes in, it goes without.

A hundred grams of chicken, twenty of protein. Nearly everyone counts the weight of the food as protein. But chicken breast is a muscle, and mostly water: 100 grams gives you just over 20.

How much, when, from what

Per day. 1.2 to 1.6 grams per kilo: 1.2 is the floor, 1.6 the target if you lift weights. If you're carrying extra weight, work from your healthy weight. At 75 kilos that's 90 to 120 grams. Going higher gains your muscles nothing, and your kidneys work harder.

Per meal. 20 to 40 grams depending on your size, about 0.4 per kilo: the dose that gets the site going. At 75 kilos, four meals of 30 or three of 40.

On the plate. Meat and fish have about 20 grams of protein per 100, so your 30 is 150 grams of chicken, lean beef or salmon. By eye, a piece the size of your hand, fingers included: the measure grows with your frame. Parmesan has about 35 per 100, tuna in brine 25, mozzarella 20.

Breakfast first. Two eggs and a Greek yoghurt, which has about twice the protein of an ordinary one, plus a handful of nuts. They fill you up more than toast or cereal: no hunger before lunch.

Lunch and dinner. Choose your protein first: vegetables and protein, carbs last. Pulses count, but they come with a lot of carbs, and you need 15 to 20 per cent more plant protein.

All you need is one number, yours, and the eye to spot it on a plate. Start with tomorrow's breakfast. The muscle you feed today is the one that will carry you in twenty years' time.