This is The Guardian.

Hi, Ian here.

The Science Weekly team are on a two-week break for the Christmas holidays.

So for the next four episodes, we're going to be bringing you some of our favourites from 2025.

Starting with this episode about something we might have all felt instinctively before,

but now has been proven by science,

that at certain points in our lives we age faster than others.

We ask why this happens and if there's anything we can do to put the brakes on.

I hope you enjoy it.

One day you're able to run for miles, stay up late partying and eat whatever you want.

Then suddenly, seemingly out of nowhere, your back hurts.

A single drink gives you a hangover.

You can't shift those last few pounds.

It feels like you've aged years, almost overnight.

Now, science is showing that that feeling could be what is happening biologically.

Rather than a gradual decline,

researchers are finding increasing evidence that our bodies change

in rapid bursts at around 40, 60 and 80.

So today, why do we go through periods of dramatic ageing? And is there anything we can do to prevent it?

I'm InSample, the Guardian Science Editor, and this is Science Weekly.

For a long time when it came to ageing, the working assumption was that it happened in a linear way.

We accrued damage steadily over the years, like old jumpers gathering holes.

...