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Horizon: Sugar v Fat

Horizon: Sugar v Fat

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As the New Year diet clamour about the evils of sugar rolls on, Horizon weighs in with a brutally simple contribution. Yes, sugar is bad, but so is fat: which is worse for you?

The current furore comes after decades when low-fat foods have been pushed as healthy options, even if stuffed with hidden sugars. But in the US, sugar is increasingly branded as addictive, deadly, even “toxic”, as Doctor Xand van Tulleken, who lives there, can attest.

He and his brother Dr Chris are identical twins and should therefore be perfect for a simple scientific experiment: if Chris eats sugar and carbs galore but no fat, while Xand eats a high-fat, protein-rich diet, who will come out better? Are all calories born equal?

The twins tour the swings and roundabouts of each regime: protein makes you feel fuller, but without sugar your brain struggles under pressure. And of course, both diets look quite revolting.


Doctors Chris and Xand van Tulleken, who are identical twins, go on month-long diets comprising high volumes of fat or sugar to find out which is worse for the human body. The effects on their health are both shocking and surprising, but they also discover their biggest enemy may have been hiding in plain sight.

Cast & Crew

Contributor Chris van Tulleken
Contributor Xand van Tulleken
Director David Stewart
Producer David Stewart
Series Editor Aidan Laverty

Documentary Science

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