Episode 2: Horizon Special: What’s The Right Diet For You?

If you’ve not already read my blog post about episode 1, please read it first.

As we saw in episode 1, the three groups of overweight volunteers were given different diets according to what makes them overeat, “instead of reaching for the latest fad diet,” said Professor Tanya Byron. As a personal trainer in London with over 12 years experience helping clients lose weight (including one client who was over 30 stone), I have to disagree and say that intermittent fasting counts as a fad diet.

The first month’s progress of each group was followed in this episode:

“Constant cravers” ¬†group (genetic causes)

This group (faulty genes which made the individual feel hungry all the time) was put on the intermittent fasting diet.

Dr Giles Yeo conducted an experiment to see if this group were biologically programmed to notice food more. Members of all three groups were given eye tracking glasses to measure what they looked at most, and left to roam around a funfair with plenty of junk-food treats on offer. The “constant cravers” group looked at food over double the number of times as the other groups.

Dr Yeo’s suggested strategy going forward was that this group should be aware of the advertising ploys of the junk food industry, and re-programme their brains to view it as a battle with the junk-food companies trying to trick them into eating unhealthily. By seeing it as a “them and us” battle with food companies rather than an internal battle against food cravings, this change in attitude is designed to empower the group members.

“Emotional eaters” group (psychological causes)

This group was put on a group-support low calorie diet.

The root cause of emotional eating can sometimes be traced back to a traumatic life event, often in childhood, such as abuse, or harsh punishment involving food deprivation.

A brain scan experiment showed that the reward circuits of the brain in anticipation of a food treat (in this case chocolate milkshake) lit up far more strongly after the subject was put into a depressed mood. This showed the strong link between trauma and the desire to comfort eat.

For this group, the key was to provide alternatives to food as a coping mechanism. The strength of diet companies like Weightwatchers and Slimming World is the weekly group meeting, where members are praised/encouraged at the weekly weigh-in. There are also online communities where members are encouraged to message and support each other through their weight-loss journey. (A brief plug for my Fitness Buddy network here: there’s a Weight-Loss Buddy option, and it’s totally free.)

“Feasters” group (hormone problems)

This group was put on the high protein low GI carbs diet, which was dubbed the ‘fullness diet’ to make them feel full sooner, without eating foods which cause them to pile on weight. The recommended proportions were to fill half the plate with veg, a quarter of the plate with protein (fish or meat) and a quarter of the plate with low GI carbs.

The carbs they suggested were basmati rice or pasta. I think better choices would be boiled sweet potato, which has a much lower GI (under 50) than ordinary potatoes. Beware, the glycemic index rises if sweet potatoes are roasted, so boiled is the better option. Sweet potato has more micronutrients than either basmati rice or pasta, so it’s a better choice in my view.

A really valuable tip for anyone who dislikes vegetables, is to blend them into a thick soup, which has the added benefit of staying in the stomach for longer and making you feel full sooner, even more than if you ate the same veg in its solid form. The group found that their appetites were satisfied with this thick soup.

One thing I disagreed with was the advice for this group to snack on fruit. Two or three portions a day is fine, but there was no warning that any more than this will easily convert in the liver to fat, due to the fructose.


Dr Jason Gill, and Exercise Scientist from Glasgow University, explained the importance of combining good nutrition with exercise. ¬†All three groups were given an exercise regime, but only after a ‘control’ week’ of measuring daily activity levels with an accelerometer.

In the control week, an average of 8,000 steps a day was recorded. In the second week, a personal trainer took them through an exercise regime for three out of the seven days. On the exercise days, over 11,000 steps a day were recorded on average, but on the non-exercise days activity levels fell below even the control week (by around 1,000 steps). This was the “compensation effect” where you slack off the day after exercise as a perceived reward, or the feeling that you don’t need any exercise the next day.

To overcome this, Dr Gill recommended the group members get a pedometer to measure their activity on non-workout days, to make sure they don’t slack off.

Unfortunately, there was no mention of the most effective exercise for fat loss: muscle-building exercise (known as resistance exercise). The more muscle-mass you have, the higher your resting metabolic rate, which is the biggest fat-burner 24 hours a day.

My main complaint about diets with excessive calorie restriction is that you lack the energy to do effective workouts to build the muscle, and this includes carbs, the body’s favourite fuel for exercise. The intermittent fasting days would be a total write-off for exercise.


A supermarket shopping trip experiment, with one team well-rested and the other team sleep-deprived, showed that we make poor food choices when tired. The tired team bought 50% more calories than the rested team, particularly things like high-sugar breakfast cereals.

The lesson: plan ahead, make a healthy list, and stick to it. Tiredness really does contribute to weight gain by lowering your resolve. There are other reasons too, such as hormonal effects, and less chance for your body to repair and re-charge at night, which compromises its ability to burn fat.

Results after 1 month

After the first week, the average weight loss across the groups was 3 lbs. However, it was pointed out that this is mainly glycogen and water, not fat. I was beginning to wonder when this distinction between fat loss and weight loss would be made, as it wasn’t mentioned at all in episode 1.

When you start a restrictive diet, you burn your glycogen stores (carbs stored in your liver and muscles), and as each gram of glycogen is bonded with around 3 grams of water, you also lose a lot of water, which is emphatically not a good thing as you then become dehydrated.

After a month, the total weight loss was 53 stone (when everyone’s weight loss was added up), but unfortunately there was no breakdown of which group lost the most weight, and no mention of how much of this weight was fat loss. What we did learn was that the average reduction in body weight was 4%.

I’m really surprised they didn’t tell us how much fat they lost, or indeed how much muscle they gained. I find it really odd that muscle-growth has not been mentioned, as this is the single most effective exercise strategy for long term fat loss, when combined with a long term healthy nutrition plan (not a restrictive diet).

Maybe we’ll find out how much fat they lost in the final episode. And maybe the concept of muscle-mass will finally be explored.

Dominic Londesborough is a personal trainer in London.