Intermittent fasting is no better than a traditional calorie-restricted diet when it comes to losing weight, a study suggests. People who ate all of their calories within an eight-hour window lost a similar amount of weight as those who counted calories but ate whenever they wanted.
Intermittent fasting has grown in popularity in recent years, with celebrities such as Jennifer Aniston, Mark Wahlberg, Beyoncé and Nicole Kidman believed to be fans of the regimen. Proponents of the time-restricted eating regimen claim it is easier to stick to than meticulously having to count calories.
The research, published in the journal Annals of Internal Medicine, evaluated 90 adults who were randomly assigned to one of three groups: eight-hour time-restricted eating from midday to 8 pm only; calorie restriction, with intake slashed by 25 per cent; or no change in calorie consumption, with eating taking place over ten hours or more throughout the day.
The intermittent fasting group did not count calories or have clear dietary restrictions. Both groups regularly met with a dietitian. Participants who engaged in time-restricted eating ate 425 fewer calories per day than the control group and lost about 10 more pounds than the control group after one year.
The calorie-restricted group ate when they wanted to consume 405 fewer calories per day and lost about 12 more pounds after one year compared to the control group. Participants showed high adherence to both approaches and reported no adverse side effects from either.
‘Time-restricted eating (TRE) has become a popular weight loss regimen,’ said dietitian and lead study author Shuhao Lin. ‘The sudden increase in popularity of TRE is mostly likely due to its sheer simplicity and the fact that it does not require persons to count calories to lose weight.
Time-restricted eating, also known as intermittent fasting, involves switching between days of fasting and days of eating normally. These fall generally into two categories – time-restricted feeding, which narrows eating times to 6-8 hours per day, also known as the 16:8 diet, and 5:2 intermittent fasting.
Followers of the eating plan fast for 16 hours a day, and eat whatever they want in the remaining eight hours – typically between 10 am and 6 pm. This may be more tolerable than the well-known 5:2 diet – where followers restrict their calories to 500–to 600 a day for two days a week and then eat as normal for the remaining five days.
In addition to weight loss, 16:8 intermittent fasting is believed to improve blood sugar control, boost brain function and help us live longer. Many prefer to eat between noon and 8 pm as this means they only need to fast overnight and skip breakfast, but can still eat lunch and dinner, along with a few snacks.
The drawbacks of the fasting plan may be that people overindulge in the hours they can eat, leading to weight gain. It can also result in digestive problems over the long term, as well as hunger, fatigue and weakness.
This isn’t the first study to suggest that intermittent fasting may not live up to the hype. A February study in mice by researchers at Mount Sinai, for example, found that intermittent fasting caused disease-fighting white blood cell count to plummet as much as 90 per cent. This increases the risk of infection, heart disease, and cancer.
Additionally, research published last August found that Americans over 40 who ate one meal per day were 30 per cent more likely to die from any cause in 15 years than those who ate three. Still, the researchers of this new study feel that the findings could be a step in the right direction for intermittent fasting.
‘Evidence shows that when persons with obesity limit their eating window to 6 to 8 hours per day, they naturally reduce energy intake by 350 to 500 calories,’ Mr Lin said. ‘From a clinical standpoint, these findings are paramount.’
Mr Lin said that one reason people stray from traditional dieting is frustration with counting calories every day. However, time-restricted eating regimens ‘can sidestep this requirement by allowing participants to simply “watch the clock” instead of monitoring calories, while still producing weight loss and cardiometabolic health improvements.’
Therefore, this could lead to people sticking to the diet for longer periods of time, producing lasting weight control in those who are overweight or obese.
The authors of an accompanying editorial from the Anschutz Health and Wellness Center and Division of General Internal Medicine, University of Colorado School of Medicine, say that the intermittent fasting group likely consumed fewer calories because they had access to a dietitian to help them make healthier food choices.
They emphasize that the results of this study highlight the substantial individual variability in weight loss using these intermittent fasting and calorie counting and that further research is needed to determine who would most benefit from each of these interventions. More than 73 per cent of US adults are overweight, along with 40 per cent who are obese, according to the Centers for Disease Control and Prevention.
