Twelve places where ageing happens — and where you can push back.

Damage accumulates in the DNA faster than the repair systems clear it, and some of it becomes permanent.

Every cell is copying three billion letters, over and over, under attack from sunlight, chemistry and its own metabolism. Mistakes are normal; the repair crews are very good. Ageing is what happens when the mistakes outpace the crews.

Not much directly, and be suspicious of anyone selling you otherwise. What is well established is what causes the damage: tobacco, too much sun, heavy alcohol, and the diagnostics that catch the consequences early.

The chemical marks that decide which genes are switched on drift with age, so cells begin doing the wrong job for the tissue they are in.

Every cell carries the same book. The epigenome is the set of bookmarks telling a liver cell to read the liver chapters. With age the bookmarks slide, and cells start reading the wrong pages.

This is the hallmark the frontier is most excited about, because partial reprogramming has reversed it in animals. In humans it is not a treatment yet. What you can do today is the ordinary set — sleep, exercise, not smoking — which tracks with slower epigenetic ageing in the clocks that measure it.

The cell’s recycling system — breaking down its own damaged parts so the material can be reused — becomes less active with age.

Your body’s clean-up crew. It takes old, broken cell parts, breaks them down and builds new ones from the pieces. When it slows, the debris accumulates, and that accumulation is a large part of what ageing looks like from the inside.

Going without food for a stretch is the strongest everyday lever — time-restricted eating or a longer fast. Hard exercise does it too. Coffee, green tea and olive oil each nudge it. Rapamycin is the most convincing drug and remains prescription-only and under study.

The organelles that make the cell’s energy become fewer, leakier and less efficient, and the damaged ones are cleared more slowly.

Mitochondria are where being alive is paid for. Tiredness that is not sleepiness is often this. So is a good deal of what people call feeling old.

Exercise is the only intervention that reliably builds new mitochondria — endurance work especially, and interval work most efficiently. No supplement comes close, whatever the label says.

The reserve of cells that replaces worn-out tissue shrinks and becomes less responsive, so healing slows and tissues thin.

Every tissue keeps apprentices in reserve to replace the workers who wear out. With age there are fewer apprentices and they are slower to answer the call. It is why a cut heals slower at sixty than at sixteen.

Nothing you buy. What protects the reserve is the unglamorous list — sleep, protein, resistance training, not smoking. Stem cell clinics selling injections for ageing are, at the time of writing, selling ahead of the evidence.

A low, persistent, body-wide inflammatory state that rises with age even without infection — often called inflammaging.

Inflammation is how a body fights and repairs; it is meant to flare and then stop. This one never stops. It is quiet enough that you do not feel it, and loud enough to damage tissue for decades.

Sleep, weight, muscle, oily fish, and treating gum disease and other quiet infections. This is also the hallmark most visible in an ordinary blood test, which makes it one of the few you can actually watch.