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This is Discovery from the BBC.

I'm Jim Elkili, and in today's programme,

I'm in conversation with a leading scientist about their life and research.

Welcome to the Life Scientific.

Many of us think we're in control of what we eat,

and that this, coupled with what we do, dictates our shape and size.

It's physics, after all.

If you eat too much and move too little, you put on weight.

Do the opposite and you lose it.

Genes, the theory goes, have minimal if any effect on our weight.

But what if we're wrong?

What if our genes have a powerful influence over how we put on weight

and why many struggle to lose it?

...