The real reason so many diets don’t work
And it has nothing to do with willpower
THe UK has some of the highest rates of obesity in the world and ever since Boris Johnson’s brush with Covid-19 there has been a flurry of initiatives to tackle the problem.
This includes the recently announced plan to give overweight people clothes vouchers and free theme park rides if they hit certain health targets. But how many of these initiatives will make a real difference? Too few, I fear.
Take, for example, the NHS Weight Loss Plan, which you can download free as an app on your phone. It is slick and a lot of money has clearly been spent on developing it. But is it effective at helping people lose weight? The answer, according to a recent study by the University of Oxford, is a resounding ‘no’.
For the study, the scientists recruited 512 patients with an average body mass index (BMI) of 35 — putting them into the ‘obese’ category — and randomly allocated them to one of three weightloss programmes: the NHS Weight Loss Plan, Slimming World Online (which offers standard calorie-control advice) and Rosemary Online (which no longer exists). There was also a control group, who were asked to continue as normal.
The participants were supposed to stick to their allotted programme for eight weeks, then report back on how much weight they had lost.
The results were disappointing. People following the NHS plan lost an average of less than 3 lb (1.3 kg), which was roughly the same as the control group, while those allocated to Slimming World lost 3.7lb (1.7kg) and those following Rosemary Online lost 5 lb (2.3 kg).
ASKINg patients to do these programmes was, the researchers concluded, at best ‘only marginally superior to no intervention’. So why were the changes so small? I downloaded the NHS app and had a look. There is plenty of sensible advice, and I am a fan of its free exercise programmes, but I was disappointed to see that many of the recipes offered were really low in fat and high in carbohydrates. As to dairy, it recommends that we go for skimmed milk and zero-fat yoghurt for weight loss.
Yet we have known for a long time that low-fat diets are not a good way to lose weight or improve health. In a study called Predimed, 7,447 overweight Spaniards were randomly allocated to either a lowfat diet or a Mediterranean diet, where they got 40 per cent of their calories in the form of fat, mainly oily fish, nuts, olive oil and dairy.
The trial was due to run for six years but was stopped early because those on the higher-fat Mediterranean diet were doing so much better, with 30 per cent fewer heart attacks and strokes and a 50 per cent lower risk of developing type 2 diabetes, compared with those on the low-fat diet.
Other studies have also shown the failure of the low-fat approach. The Women’s Health Initiative Dietary Modification Trial, which began in 1993, involved 48,000 American women randomly allocated to either a low-fat diet or to continue their usual eating habits. Those asked to go low-fat got extensive counselling and support. And, hurrah, they managed to cut their fat consumption significantly.
But when the trial was stopped after eight years, those who had gone low-fat were no healthier than the control group when it came to weight loss, heart disease or cancer.
As for dairy, not only is there no compelling proof low-fat versions are healthier, but there is mounting evidence that full-fat versions are better for you. In a study published last month, researchers in Sweden assessed the impact of eating full-fat dairy on more than 4,500 middle-aged volunteers.
To accurately measure how much they were consuming, the volunteers had their bloods tested for levels of two fatty acids, called heptadecanoic acid and transpalmitoleic acid, which are found almost exclusively in dairy fats. Then the volunteers were monitored for more than 16 years.
It turned out that the biggest consumers of full-fat dairy had the lowest rate of heart attacks and strokes. As the researchers point out, this was no fluke because their findings are similar to those found in other studies, involving more than 42,000 people, carried out in countries including the U.S., the UK and Denmark.
Regarding weight, other studies have shown that people who eat full-fat dairy usually put on less weight and have lower rates of obesity than those who don’t — probably because fat is more satiating than carbs. Although, sadly, that doesn’t give you licence to eat huge amounts of cheese.
However, if you want to lose a decent amount of weight, by which I mean half a stone or more, then it is becoming increasingly clear that going on a standard slow-andsteady, low-fat high-carb diet is unlikely to result in success.
Research by the Oxford group, who carried out the study I described earlier, where they asked patients to try an 800-1,000 calorie low-carb approach, resulted in an average weight loss at eight weeks of 9.5 kg (1 st 7 lb) and big improvements in blood sugar levels — changes that were far greater than in a control group offered standard NHS healthy-eating advice.
I know which I would do.