At the beginning of this year, on BBC2, to coincide with the usual New Year dieting crazes, a series of three programmes showed a scientific experiment concerning dieting, led by some of Britain’s leading obesity scientists. Called ‘What’s the Right Diet for You’, it involved 75 guinea-pigs – people who were obese and willing to undergo various tests and instructions to see if they could lose weight - who had been entered into the experiment after their genes, hormones and psychological profiles had been assessed.
Now if dieting is to be successful, the experts argued, it must be tailored to the individual. People are overweight because of over-eating, but different people over-eat for different reasons. The experiment involved dividing participants into 3 different groups. These types of over-eaters are:
‘Feasters’, who, once they start eating, cannot stop. ‘Constant cravers’ have ‘hungry genes’ which lead them to eat throughout the day. In the third group of ‘emotional eaters’ are people who eat for psychological reasons, those who use food to manage their emotional state
Feasters, it is thought, produce less of a hormone that tells them when they have eaten enough; this is GLP1, one of a number of gut hormones that tells the brain when sufficient food has been consumed. When all the participants arrived at Liverpool Hope University for the days of the experiment, a celebratory evening meal was laid on as part of the welcome. Little did they know that this was the first test! Food was continually available so that diners could eat as much as they liked. They did not yet know that, on the basis of their assessments, they had already been arranged into their groups. The programme showed that the feasters lived up to their designation by eating much more than the other two groups.
The individualised strategy for weight loss for festers involves a diet incorporating increased protein and low GI foods, which makes your feel fuller more quickly and for longer, to counteract the lack of signals of fullness from the gut hormones. Foods such as meat, beans, lentils, grains and cereals will deliver this. It was interesting to note that pasta (and quality bronze pasta is now available in Britain) was recommended but potatoes rejected.
Another, more traditional way to increase a sense of fullness from a normal portion of food is to chew it thoroughly. People who eat too fast, the scientists confirmed, tend to eat too much. Thus the suggestion to use chopsticks for eating more slowly might help those particularly desperate (maybe just being mindful of what you are doing is all that is needed: not watching TV while you are enjoying a meal and employing some conscious chewing of food). Eating more slowly increases the levels of the fullness hormone GLP1 and well as giving less time to eat something more!
Constant cravers were identified from genetic tests. They crave food and pay more attention to sources of food in their immediate environment. The diet that should work for them is the 5:2 diet, where they can eat normally for 5 days then follow a calorie-restricted 2 days. At least they only have to face the diet for 2 days a week!
The emotional eaters were at the beginning put through a fake driving test to raise stress levels and to see what their reaction was – which was increased food intake afterwards compared to other groups. These dieters will benefit from joining weight-loss groups because the emotional support does help them to lose weight. In the programme a group of large men and women who were emotional eaters had to abseil down a lighthouse, despite protestations and tears, to show themselves they can overcome adversity and obstacles and to increase their belief in themselves.
All groups in the experiment initially lost weight but then the dieting became harder. Participants were finding that their weight loss reached a plateau where no more pounds were shed, or in some cases they even put on weight again. The scientists in the next experiment busted the myth that slim people have a higher metabolic rate. Actually, the opposite is true: if you are bigger, your have a larger heart and other organs which require more energy to work. Thus when you have lost weight, you need less to run your body and unless you reduce your food intake again, you will stop losing weight. Consequently, the new habits on these diets are lifelong changes to eating.
For the constant cravers, it is the genes responsible for their over-eating that cause the difficulties in continuing to shed the pounds. Normally, as fat is lost from the body, the levels of a hormone called leptin also decreases and this signals to the brain that fat stores are decreasing and need replenishing. Everyone experiences this. However, those with these ‘obesity genes’ experience a trick – the genes tricks the brain into believing that the levels of leptin are lower than they really are, so that the brain signals that fat stores need replenishing urgently. In one test, half the group breakfasted, half did not. Those who missed breakfast craved the fatty, sugary high calorie foods when shown images of these and of healthier foods. It turns out that for 75% of all dieters, having breakfast is part of a successful diet, because it helps you to make healthier choices of foods later in the day.
For the emotional eaters, lapses in the diet usually lead to a common psychological response, that of over-eating again. These dieters need the coping strategies not to regress, not to abandon their diet, after a lapse. To do so is an example of ‘catastrophic thinking’. In one experiment, those who thought they had lapsed by eating the cake offered to them went on to eat, at a second round of cake, 8 times more than those who were told a white lie that the cake was low in fat, sugar and calories in order to lead them to think that they had not broken their diet. So, the message is: we all have lapses, don’t give up!
These strategies seemed to be successful for the participants. Also, a final point was made concerning exercise. Exercise helped all 3 groups to keep the weight off, but it does not help people to lose weight when they first start, if they are not putting an end to over-eating. Walking up stairs, going by foot rather than on the bus or in the car, helped to burn as many calories as getting to the gym once or twice a week.
Rather than looking at a diet itself – whether it’s the latest fad or some superfood or other – look at yourself and try to work out what approach may be suit you! To follow up try www.bbc.co.uk/rightdiet where you can take a test to find out which type you are. However, I found the questions rather simplistic and was not convinced of the outcome!
Veda West BA BSc MNIMH