TV Review: Horizon Special: What’s The Right Diet For You?

Last night’s episode of this Horizon Special was fascinating but flawed in my view (Monday 12 January 2015 on BBC2). The second is tonight at 9pm, and the final episode is on Wednesday evening. I’ll go into the reasons for my reservations in tomorrow’s blog post.

As a personal trainer in London with a special interest in all things nutrition, I make time to watch programmes like this. I was impressed by the number of leading experts involved in this, the largest nutrition experiment of its kind in the UK.

Eleven million Brits go on diets and 80% fail, we were told in the intro. 75 overweight volunteers took part in this documentary, and after detailed analysis (which lasted 5 days) they were divided into 3 groups according to what the experts identified as their main problem: their hormones, their genes, or their emotions. Then they were given tailored diets designed to address these issues.

The presenters were Dr Chris van Tulleken, and clinical psychologist Professor Tanya Byron. In what is the largest study of its kind in the UK, an array of experts were involved: Dr Giles Yeo (a geneticist), Professor Fiona Gribble (a gut hormone specialist), Professor Susan Jebb (a nutrition scientist), Professor Paul Aveyard (a behavioural scientist).

1st Group: “Feasters” (primary issue: gut hormones)

This group lacked sufficient “feel-full, stop eating” hormones in their gut, primarily GLP1 which has a strong influence on appetite. As a result they don’t feel full after eating a large meal, and keep on eating, hence their weight-gain.

In the sushi-eating experiment, some ate 12 plates of sushi at 150 calories per plate, a staggering 1,800 calories.

2nd Group: “Emotional Eaters” (primary issue: psychological)

This group were given a deliberately stressful driving test, and their cortisol levels were tested before and after their nerve-wracking experience. Cortisol is one of the ‘stress hormones’. They were then monitored as they attacked the buffet bar.

Emotional eaters are drawn to sugary, carbohydrate-rich foods, as a form of coping mechanism or ‘comfort eating’. As the experts pointed out, a better coping mechanism is a bout of exercise, but this category of overweight people turn to food.

3rd Group: “Constant Cravers” (primary issue: genetics)

A group of genes has now been identified which disrupt signals to the brain which tell the body to stop over-eating once body-fat has exceeded a certain level.

In the experiment for this group, strength of desire for different foods was measured by carefully calibrated grip-force machines, which the people in the group squeezed when presented with various foods. The greater desire, the harder they were to squeeze. Foods high in fat/sugar/salt triggered the strongest responses.

The experts then devised the following diets for each group:

1st Group: High Protein/Low Glycemic Diet

This diet was devised for the “feasters”, the group with the problematic gut hormones.

The combination of high protein and slow-release carbs was designed to elevate the ‘feel-full’ hormones, so they would feel fuller for longer and eat less throughout the day. Bread, fruit, potatoes, and other high GI foods were excluded.

I had a personal training client in north London who went on the Atkins diet (against my advice) and although he lost some weight, he suffered low energy and mood swings. It will be interesting to see how this group survives in the next two episodes.

2nd Group: Low Calorie Diet with Group Support

The “emotional eaters” were given a strict calorie-controlled diet, which they found hard in the first few days. The key to this diet was the Weightwatchers-style group support designed to activate the motivation areas of the brain, in order to overcome the negative emotions which triggered comfort eating.

They were also given a confidence-building challenge of absailing down a lighthouse to show them they could do things they previously thought impossible.

I have several personal training clients in London who could be classed as emotional eaters, and my methods are rather different. However, I’ll go into this in more detail when I review the next two episodes.

3rd Group: Intermittent Fasting

This group, the “constant cravers” with the genetic problem, were given a strict diet of just 800 calories a day, two days a week, and they could eat normally for the rest of the week (although it wasn’t explained what ‘normally’ meant). These 800 calories could be made up of meat, fish, eggs, and vegetables. No fruit or other carbohydrates were allowed.

The thinking behind this diet was to get the group into a ketonic state, where in the absence of carbohydrates the body turns to fat stores for its primary fuel source. Their urine was tested for ketones, and found to be high, which meant the diet was ‘working’.

Personally I’m dead against this diet, as I tell all my personal training clients in London who ask me about it. I’ll go into the reasons why in my next blog post when I review the second episode of this Horizon Special.

Dominic Londesborough is a personal trainer in London.