Dieting can be tedious over the long term. Sure, counting calories over a week or two might be feasible, but forcing yourself to do it every day for months? Excruciating.
If this struggle feels familiar, a new year-long trial may offer some relief. The research found that a certain type of intermittent fasting helped participants lose slightly more weight than traditional daily calorie counting – and may be easier to stick with, too.
The study, published in the Annals of Internal Medicine, compared two dietary strategies in 165 adults who were overweight or obese.
One group followed a 4:3 intermittent fasting plan (four days of normal eating, three days of restricted intake), while the other cut calories every day.
Both groups also had access to exercise support and behavioural coaching – including food logs, tailored feedback and a gym membership.
At the end of 12 months, those on the fasting plan had lost an average of 7.6 per cent of their body weight, compared to 5 per cent in the daily calorie restriction group.
They also showed slightly more favourable changes in blood pressure, cholesterol and fasting glucose levels.
What is 4:3 intermittent fasting?
Unlike time-restricted eating (TRE), which involves eating within a set daily window (say, 10am–6pm), intermittent fasting (IMF) focuses on significantly cutting back on food a few days a week.
In this trial, participants on the 4:3 IMF plan chose three non-consecutive 'fast' days per week (such as Monday, Wednesday, and Friday).
On those days, they consumed just 20 per cent of their usual calorie intake — roughly 400–600kcal for women and 500–700kcal for men. On the remaining four days, they could eat freely, though healthy food choices were encouraged.
“Counting calories can be cognitively burdensome,” Prof Danielle Ostendorf, co-author of the study, told BBC Science Focus. “Only having to do that three days a week might have made it easier to adhere to over time.”
Despite both groups being prescribed the same overall calorie target across the week, the fasting group ended up achieving a slightly greater weight loss.
But while the study demonstrated that 4:3 intermittent fasting could be a promising option, it’s no silver bullet.
“The study's main finding was that a 4:3 approach gives more weight loss than conventional calorie restriction,” said Dr Adam Collins, a nutrition scientist at the University of Surrey who was not involved in the research.
“Yet, this is not a magic property of the 4:3 approach per se, but because they achieved a bigger calorie deficit.
According to Collins, some clues lie in not just what was measured, but what wasn’t.
“Those assigned the 4:3 diet were only requested to record their intake on 'fast' days, but we know from early studies on intermittent energy restriction (especially alternate day fasting), that there is a tendency for some people to eat less on non fast days too, whether that’s unconscious or subconscious,” he said.
In short, measuring calorie intake for the fasting group only on fasting days may have underestimated their true calorie intake.
“Nevertheless, it does support the notion that, in the real world, intermittent energy restriction protocols outperform conventional everyday calorie restriction both in terms of compliance and results,” Collins added.
So, should you try it?
Ostendorf and lead author of the study Prof Victoria Catenacci were cautious about making blanket recommendations. “For people seeking to lose weight, they should choose a dietary strategy that they feel they can stick with long term,” they said.
“We think our study’s findings show that 4:3 IMF can be considered as an additional evidence-based dietary weight loss option to choose from.”
About our experts
Danielle Ostendorf is an assistant professor of Kinesiology, Recreation, and Sport Studies at the University of Tennessee Knoxville. Her work integrates epidemiology, exercise physiology, psychology, and dissemination and implementation (D&I) science to design, optimize, and evaluate lifestyle intervention programs for adults. Her research has been published in journals including Nutrients and the American Journal of Public Health.
Victoria Catenacci, MD, is an associate professor of medicine, endocrinology, metabolism and diabetes at the University of Colorado Anschutz Medical Campus. Her research has been published in journals including Nature Reviews Endocrinology and Physiology & Behavior.
Read more: