There is no evidence the 5:2 diet prevents heart disease despite misleading headlines based on a recent study, according to the NHS.
Yesterday, various news outlets reported on the results of a comparison between following the 5:2 diet and a standard low-calorie diet.
The 5:2 diet involves eating “normally” five days a week and restricting your calories to 500-600 per day for the other two.
It’s based on the principles of intermittent fasting and originally gained popularity about five years ago.
A new study from the University of Surrey and King's College London, funded by LighterLife, claims that the 5:2 diet clears fat from the blood quicker after eating meals than more simple low-calorie diets, thus reducing the risk of cardiovascular disease.
However, this trial was only carried out on 41 people so is not statistically significant, according to an analysis by Bazian for NHS Choices.
The researchers divided participants, who were all overweight: 24 followed the 5:2 diet and 17 followed a traditional low-calorie diet.
Those on the 5:2 diet were given four Lighterlife food packs, which provided approximately 25 per cent of their estimated calorie needs. They ate these for two consecutive days and on the remaining five days they could eat what they wanted but were advised to make healthy choices.
The participants following the traditional diet were advised to consume 600 calories fewer than they would do normally but could choose what they ate.
The researchers found that there was no real difference in either the amount of weight lost or the time it took for the pounds to drop off.
Out of the 41 participants, 27 reached their five per cent weight loss target – 15 in the 5:2 diet group and 12 in the traditional diet group.
The average 5:2 dieter lost 5.4 per cent of their body weight, and the basic low-calorie dieters lost five per cent.
It took 5:2 diet participants an average of 59 days to achieve their five per cent weight-loss target and those following the traditional diet 14 days longer at 73 days. However, the difference did not reach statistical significance.
What’s more, there was no difference between groups in blood sugar control after eating.
The only claim that does stand up is that the 5:2 dieters had reduced triglyceride blood fats immediately after eating.
The differences between the two diet groups were so small that they cannot be considered significant.
And despite the evidence that certain blood fats were lower immediately after eating for those following the 5:2 diet, the idea that this will have long-lasting effects and reduce risk of heart disease is too bold a claim to make, according to the NHS.
As well as the very small study size, there are other limitations: participants self-reporting weight and dietary compliance is not reliable, plus all the participants were white, meaning the sample does not represent the population as a whole.
The 5:2 diet rose to popularity in the early 2010s but the jury is still out as to whether it’s healthy – many nutritionists and dieticians aren’t convinced and say more research needs to be done.
What’s more, although following the diet may lead to weight loss, it’s not a way for people to learn about the nutritional value of food.
“With calorie-controlled diets, there is still a risk of not eating enough nutrient-rich foods which may result in certain deficiencies,” Harley Street nutritionist Rhiannon Lambert explained to The Independent.
There’s also the risk of intermittent fasting diets such as the 5:2 actually promoting disordered eating.
“Diets fundamentally promote weight loss not health, and being stuck in a ‘diet mentality’ may also encourage an unhealthy relationship with food,” Lambert explains.
“Research suggests that restricting food is likely to lead to binge eating behaviours. If you restrict your body of energy for two days, you risk becoming fixated on food on the days that you’re ‘allowed’ to eat normally. This may trigger a disordered eating pattern.
“It is just another faddy diet that won’t help people actually develop a healthy relationship with food!”
Restricting your calories so severely two days a week can make people feel like they’re constantly on a diet – instead, most nutrition experts recommend focussing on what your body needs in terms of nutrition rather than the quickest way to lose weight.
“Making smarter and healthier food choices does not necessarily need to be counted in calories,” says Lambert, who is the author of bestselling book Re-Nourish: A Simple Way to Eat Well.
“By becoming engrossed in counting calories and restricting our food intake, it means becoming increasingly confused in regards to what it means to be healthy.
“Being restricted to a certain amount of calories each day isn't going to be helpful because not all calories are equal. We should remember that health isn’t immediately repairable and weight isn’t immediately modifiable.”