Intermittent fasting has been one of the most talked-about diet trends of the past decade, with everyone from doctors on social media to your neighbour up the road singing its praises.
Promoted as a simple, science-backed way to lose weight, boost metabolism and improve overall health, if you haven’t tried it yourself, you no doubt know someone who has. But a new review of the evidence suggests the results may be more modest than we first thought.
Published by Cochrane, researchers analysed 22 randomised controlled trials involving nearly 2000 adults with overweight or obesity across several countries, including Australia, the United States, China and parts of Europe and South America.
Their conclusion? Intermittent fasting may not lead to greater weight loss than traditional diets that involve cutting calories. Compared with no specific dietary advice, it also appeared to make little to no meaningful difference in weight outcomes.
“Intermittent fasting just doesn’t seem to work for overweight or obese adults trying to lose weight. It may be a reasonable option for some people, but the current evidence doesn’t justify the enthusiasm we see on social media,” lead author Luis Garegnani, from the Universidad Hospital Italiano de Buenos Aires Cochrane Associate Centre, said.
The review also found that information about possible side effects – such as headaches, fatigue or nausea – was inconsistently reported, making it difficult to draw firm conclusions about unwanted effects.
What is intermittent fasting?
Intermittent fasting isn’t a specific meal plan, instead it’s a way of structuring when you eat. Rather than focusing only on counting calories, it alternates between periods of eating and periods of fasting.
Popular versions include time-restricted eating (for example, eating only within an eight-hour window each day), alternate-day fasting, or the 5:2 approach, where people eat normally five days a week and significantly reduce calories on two non-consecutive days.
The concept gained widespread popularity in the early 2010s, helped along by documentaries, bestselling books and the late TV presenter Michael Mosley, who put the 5:2 diet on the map.
For many, it felt less fiddly than tracking every bite, with the promise that by shortening your eating window, your body would naturally burn more fat.
While eating during a specific time frame may feel easier than constantly tracking your calories, the evidence now indicates it may not offer a significant advantage over a more traditional, balanced approach to what you eat.
In saying that, if you do follow an intermittent fasting diet and it’s working for you, there’s no harm in continuing. As with most things in health, there is rarely a single solution that suits everyone. Beyond just what and when you eat, sustainable weight management is influenced by your overall diet, exercise, sleep, stress levels and any underlying health conditions.
The takeaway? Intermittent fasting may be one option among many, but it’s not necessarily a magic bullet. If you’re considering making changes to your diet, a good starting point is a chat with your GP or an Accredited Practising Dietitian to find an approach that supports your specific needs.
