Professor Tim Spector

And, again, the first thing that improved was what was going on in their brains, and they suddenly felt alert again.

And once people realise there's this connection, then, in a way, you'd have this feedback loop to say, OK, I'm not going to eat this shit food, you know, because I know it's making me feel so sick.

But until you make that connection, you're not going to know...

You'll just be in this constant state saying, well, you know, I'm just overweight.

That's why I'm tired.

Or I'm not exercising.

That's why I'm tired.

In our Zoe studies, we found that people who had a bad night's sleep desperately craved some sugary crap in the morning, right?

It's the first... You don't go for a healthy breakfast.

It's like there's some little evil thing in your brain saying, OK...

I need a quick fix.

I don't care about the rest of the day.

Just get me through the next hour.

There are a lot of studies now that stress...

which we thought of as a sort of external psychological event is actually a physiological one and is actually driving inflammation.

It's directly affecting your immune system, which is then sending these signals to your brain to change your behavior.

And this, I think, is very much the heart of what seems to be happening in depression.

What I've been finding out is that it's detecting a change in the immune system that's switching on to the stress mode.

And the stress mode then triggers these different behaviors in your brain.

And very often, it's not, you know, real stress.