The trendy 5:2 ISN’T better than conventional dieting for weight loss, study finds
If you want to reverse festive indulgence this new year, try going back to basics
AFTER weeks of festive indulgence, you'd be forgiven for jumping at the nearest fad diet to help you slim back down.
But, when it comes to weight loss, going back to basics really could be your best bet - and the fashionable 5:2 is no different.
This popular eating plan is a type of intermittent fasting, and involves five days of eating freely with just 500 total daily calories consumed the other two.
However, while it sounds like an appealing way to start your 2019 health kick, new research has found it may be no more effective than a normal calorie-restricted diet.
Here David Clayton, Lecturer in Nutrition and Exercise Physiology, Nottingham Trent University, explains on why intermittent fasting is no better than conventional dieting for weight loss:
With a global diet industry , it’s clear the world is obsessed with weight loss. But what’s the best diet for losing weight and improving health?
One of the most promising diets to have gained attention recently is intermittent fasting, which the media has crowned a miracle .
But according to , when it comes to losing weight, intermittent fasting isn’t any more effective than conventional dieting.
is an eating pattern that condenses daily food intake into one time-restricted period, then fasting for the rest of the day.
One of the most popular versions of intermittent fasting is the “5:2 diet”.
This allows five days of unrestricted eating and two days (usually non-consecutive) eating a very low-calorie diet, typically about 500 calories.
The diet’s biggest appeal is the flexibility to tailor it to your lifestyle.
Enthusiasm for intermittent fasting was fuelled by data from animal studies that suggested it the risk of diabetes, cardiovascular disease and certain types of cancer.
However, few studies have actually examined the effects of intermittent fasting on humans for longer than six months.
Carrying out long-term studies that controlled diets are difficult because it’s hard to get people to stick to them, and results can be affected by outside factors.
This recent study was conducted over a 50-week period, making it one of the longest intermittent fasting studies to date. Researchers split 150 participants into three groups.
One group followed the 5:2 intermittent fasting diet (with two non-consecutive “fast” days per week eating about 500 calories), while the second group reduced daily calorie intake by approximately 20%. A third control group weren’t instructed to change their diet.
During the first 12 weeks, a trained dietitian worked closely with participants to ensure they stuck to the allocated diet. After 12 weeks, participants continued following their diet without the dietitian.
The effects of the diets were then evaluated using a number of health assessments after 12, 24 and 50 weeks.
Researchers measured body weight, body fat, insulin sensitivity (risk of diabetes indicated by ability to control blood glucose) and cholesterol.
They also analysed 82 genes linked to obesity and metabolic disease.
The study’s key finding was that intermittent fasting and daily calorie restriction both led to significant weight and fat loss compared to the control group.
But intermittent fasting was no more effective than conventional dieting for losing weight. Intermittent fasting also didn’t improve any marker of health more than daily calorie restriction.
Drop-out rates were low but similar for both diet groups, suggesting participants found these similarly easy to stick to. Other long-term intermittent fasting studies in humans .
This study essentially confirms a well-understood weight loss principle: whatever method you use, in order to lose weight you must reduce your total calorie intake.
The 5:2 diet is designed specifically to reduce your total weekly calorie intake by a similar amount as a daily calorie restriction diet. So perhaps its not too surprising that end results are similar.
The study also showed a trend for greater weight loss in the intermittent fasting group after 12 weeks, but greater weight regain (about 2kg) between 24 and 50 weeks.
This suggests that intermittent fasting could aid short-term weight loss but might not be a good method for sustained, long-term weight loss.
My own research found that people following a very-low calorie diet (550 calories) experienced reduced levels of the following day.
As high concentrations of ghrelin are associated with feeling hungry, lower concentrations of it after a very-low calorie diet suppress appetite, and could help people with short-term weight loss.
However, this study wasn’t able to show the same health improvements (such as ) that previous .
These studies used longer, more severe methods of calorie restriction (often fasting completely), which the 5:2 diet doesn’t normally include.
But that following the 5:2 diet for three months improved insulin sensitivity over daily calorie restriction diets, if the two very-low calorie days were done consecutively.
This suggests intermittent fasting might provide additional benefits if the period of calorie restriction is extended.
Whether intermittent fasting can be successful beyond 50 weeks is not yet known.
And though drop-out rates were low, the study still demonstrated that intermittent fasting isn’t immune to the gradual decline in adherence .
This means, like most diets, it’s only effective when there’s an active effort to maintain it.
Questions still remain about intermittent fasting, specifically whether all methods (such as , where you only eat one large meal in the evening) are similarly effective.
Another form of intermittent fasting, known as (where people can only eat during a fixed four, six, or eight-hour eating window) is also receiving considerable attention, with the time of the day you eat might be as important as what you eat.
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Research is underway to determine the best time to eat, how long you should fast, and how these diets specifically affect health
When it comes to dieting, there is no one-size-fits-all solution. This study showed that intermittent fasting and calorie restriction are equally effective for weight loss and improving metabolic health.
So the best, and likely most successful, diet for yourself is probably one that fits your lifestyle.
, Lecturer in Nutrition and Exercise Physiology,
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