Sugar v Fat: Horizon asks Which is Worse?

It’s an undisputed fact that in recent years our world has become fatter and unhealthier. What’s the root cause of this? It’s a question we desperately need to unlock if we’re to turn around the so-called obesity epidemic and the various health problems that go with it. Doctors and brothers Chris and Xand van Tulleken set out to get to the heart of the matter in this fascinating educational programme from Horizon: Sugar v Fat. More than just brothers, Chris and Xand are identical twins, and their identical genetic makeup provides the ideal baseline for the unique month-long experiment they’re about to embark on to measure the effects that a high-fat and a high-sugar diet have on their bodies.

In the UK, we know (or think we do) that too much sugar can lead to weight gain and conditions like diabetes. Traditionally though, we view fat as the major threat to our health, with its ability to clog our arteries, raise our cholesterol and ultimately lead to strokes and heart attacks. Meanwhile in America, sugar is increasingly being viewed as the enemy, with a school of thought known as ‘The Hormone Hypothesis’ gaining momentum. Believers blame insulin, with its known links to blood sugar levels, for driving more energy into fat and thereby causing weight gain, thickening of the arteries, raised blood pressure and all the associated health implications. Who’s right? Sugar v Fat investigates.

The doctors start by taking key measurements such as their fat-to-muscle ratio, cholesterol and insulin levels before commencing their respective diets under the close supervision of nutritionist Amanda Ursell. Xand will eat a high-fat diet which allows cheese, meat, eggs, oily fish and cream but no fruit or any other sugary foods, while Chris is on a diet high in carbs and simple sugars which comprises bread, pasta, rice, potatoes, breakfast cereals, fizzy drinks and unlimited fruit and veg.

How will their minds and bodies cope with their extreme diets? We get our first insight two weeks in, when the doctors’ wits are put to the test in the stressful environment of a city day trading room as they play at being stock traders for the day. It’s a task which demands alertness, good decision-making skills and a good memory. Which one of the brothers has the brain fuel he needs to win this head-to-head? With expert input from Professor Robin Kanarek of Tufts University, Massachusetts, the results are a great teaching resource for illustrating the effects of diet on cognition.

After three weeks on their diets, the boys face two more challenges. First they undergo the ‘hunger experiment’ which sees them eat an equal amount of calories for breakfast. Three hours later they’re offered an all-you-can-eat selection of their allowed foods for lunch. One is full after consuming a fairly modest 825 calories while the other manages a whopping 1250 calories in this single sitting, that’s half his recommended daily intake. Which one is fuller sooner? We learn about the effects that both proteins and sugars have on the hunger hormone ghrelin, shedding light on the outcome of this particular test. 12 hours later, with empty stomachs, they face a physical test in the bike challenge. After 45 minutes of pedalling, a pat of butter and a sugar gel are all they’re allowed before the final section of the challenge, an uphill race. We know that both fat and sugar are sources of energy, but which will prove the most efficient in giving their muscles the fuel they need to complete this punishing contest?

After 4 weeks, it’s crunch time and the brothers return to the lab to measure the effect of their respective diets on their weight and health. Is there a winner in the Sugar v Fat contest and an answer to the hottest question in nutrition today? As doctors, Chris and Xand thought they knew how these foods would affect them, but they’re learning things they would never have anticipated about how their bodies react. The results are both surprising and unsettling; after just one month, one of them is on the road to diabetes, and it might not be the one you’d expect.

Sugar v Fat includes research and expert analysis from both sides of the Atlantic and is an ideal video to learn about the effects of sugar and fat on the body. BBC Active offers a wide variety of programmes which are valuable resources for education, including many more from the flagship science and nature series Horizon, now in its fiftieth year. Titles from BBC Active are available in DVD and VHS format and come with a full non-theatric licence which gives schools, universities and training organisations the rights to use this powerful content in their learning delivery. Digital licensing options for those wishing to incorporate the content into online environments are also available.