HorizonExperimenting on the human body is a familiar thing. For most of us, our daily routines include the ingestion of caffeine, tobacco and various foodstuffs that we know are bad for us.
Cue identical twins, christopher & xand van tulleken, who have been investigating the effects of diet, medicine and exposure to nasty things for some time. They travel constantly; have filmed a string of successful television shows and experiment whenever possible in a bid to examine different aspects of global health and treatment.

What makes them the ideal candidates?
They sport an identical genetic make-up making them the perfect walking petri dish.Dr chris took time out of his busy schedule to talk to gallery magazine and discuss the great sugar debate and of course, judgement…

Name?
Dr christopher van tulleken

Occupation?
Registrar in infectious diseases and medical research council research fellow at ucl (for hiv studies)

Where did you receive your education?
I did my medical degree in oxford (as did my twin brother) and i trained as a doctor in london – i’ve been a doctor now for 11 years.

Who’s the oldest? You or your twin brother xand?
Xand is 7 minutes older than me.

What do you like to do in your spare time?
I get to go on lots of expeditions and research tropical medicines. I also go to places like the arctic a lot – and because i do the tv work it soaks up all of my hobby time. It can involve mountaineering, going to the rainforests – i get to see wildlife too. There isn’t really any time to do normal hobby things like…jigsaw puzzles? Do people still do them

You’ve been involved in numerous bbc science documentaries – which one has been your favourite and why?
I couldn’t possibly decide on a favourite. The children’s work for cbbc is really fun to make because it’s such clean television. We always say that the show (operation ouch!) Can be watched by any doctor in the country and they will learn at least one thing. But there’s something special about being sent all over the world so it’s all pretty good fun. I really enjoy being able to work for the bbc too – it’s an absolute pleasure. I’m a big fan of the old license fee and generally keeping the old bbc up and running.

Have you ever been in a situation where you had to make a judgement call?
Yes many times. That’s the hardest thing about being a doctor on television because your pride means you don’t want to say “i don’t know”. But of course in a hospital staff and other doctors provide a support network. You have this enormous structure of specialists who all get together and discuss complicated problems or medical issues. And so to be on your own with just your twin brother in a jungle…the biggest decisions were always “do something or do nothing.” That’s not a thing we allow in the western world – but people do have perfectly good immune systems and people recover in ways that we never allow to happen in a modern hospital.

Recently you filmed a documentary for the bbc flagship science programme – horizon. What made you embark on the fat vs sugar experiment?
I’d been to the arctic in 2008 with bruce parry and lost more than four stone and returned to the uk weighing little more than nine stone. During the expedition, xand (my twin brother) went to america and put on approximately five stone. He was almost double my weight! We both experienced enormous fluctuations. So we started researching nutrition, which we’ve always done to an extent as doctor’s with patients, but we realised that we just don’t know the answers to some very basic questions. Our programme investigated a simple question and it appealed to us because we could use ourselves to answer it. That always makes good television. The absolute zeitgeist at the moment is the “great sugar debate” – that it’s the new toxin or that it’s worse for you than crack cocaine and it’s terribly addictive. So it was a way for us to address something that seemed to be misrepresented in the media.

What was the biggest challenge you faced when conducting the experiment?
Being on a diet, no matter how benign it is, can be very difficult. I find it very difficult to have restrictions put on my lifestyle externally – and so to have a diet that removes the flavour and joy of eating, like a low fat diet, is a real task. I have great sympathy now for people who are dieting. It can be psychologically dreadful. Food for most of us is a very certain point of joy in all of our lives. Whatever is going on in our relationships, whatever is going on in our jobs, we can eat a nice meal and immediately get some pleasure out of it.
The hardest thing about doing the programme was trying to find something responsible and factual in an area of science and medicine that is so confused and involved, intricately, with an ‘industrial argument’.

What do you mean by ‘industrial argument’?
There a lot of people with immensely vested interests on both sides of this debate – in the manufacturing, health and fitness trade. It’s incredibly difficult to sort it all out. So finding a solution was key and the bbc drafted in the best and most qualified researchers in the world to work with us to ensure we got a clear message. It’s a very important health message that we didn’t want to get wrong.

Weren’t your findings predictable? More sugar results in a higher risk of diabetes? More fat in the diet results in weight gain?
In reality what happened was something very different. Xand, on his very low sugar diet, started to produce less insulin and be less sensitive to it – which is the opposite of what you’d expect on a low carbohydrate diet, whereas the tests of my insulin function were much better. It was very unexpected. Xand appeared to become closer to becoming a diabetic than i did on a high sugar diet. At the moment in the press, there is a tendency to say “sugar is the new fat” and “avoid at all costs”.
I generally agree that lots of sugar, especially refined sugar, is bad for you, but to simply believe that you will solve the obesity problem by restricting carbohydrate intake is a bit misguided.
I need to stress the relevance of this – we are only two people. Not exactly a broad research spectrum. But what it did backup, from the evidence we gathered, which is that the modern thinking, that sugar is very toxic, is not exactly right.
It is the mixture of fat and carbs that makes food so troublesome.
Take-away food is the perfect example of this. You can eat your bodyweight in chinese food. You keep eating long after you are full. You can eat almost to the point of vomiting! That’s because the food ‘tastes’ so good. It’s that mixture of fat and sugar. The same reaction-areas in your brain light up in exactly the same way as when you introduce certain narcotics to the body.

What is the best advice for people who are dieting or attempting to live a healthier lifestyle?
Do your best to select a diet where you restrict your intake of processed food. If you buy fish from your local fishmonger, meat from the butchers, fruit and veg from the grocers and you assemble it at home using oil and spices and salt and pepper, you will find that you will regulate your calorie intake. By eating a normal diet of stuff that your grandmother recognised as food – that will help you lose weight.
Our programme wasn’t a weight loss documentary. It was about fat and sugar. Our moderate conclusion was that when you combine the two, food is so delicious that you can’t stop eating it. That’s essentially the sole message – it’s not fat and it’s not sugar but when you mix the little devils, that’s when you start seeing problems.

What advice would you give to people trying to lose weight?
If you are someone that wants or needs to lose weight you have to do several different things at once.
You have to increase your activity, which means making sure that you’re not injured. Changing the structure of your life and creating more time is essential. You have to eliminate processed foods which means asking friends or colleagues not to include you in cake runs and allow for more time to cook for yourself; eat out less and drink less alcohol, which means socialising in a different way. You have to attack the problem from all angles and accept that it is a multi faceted solution.

Gallery would like to thank the bbc and dr christopher van tulleken for their time.