It might be time to trade your calculator for a calendar.
New research suggests that fasting just three days a week could lead to more weight loss and better health outcomes than constantly counting calories.
With studies consistently showing that people struggle to stick to daily calorie restrictions, researchers said the 4:3 intermittent fasting regimen could be a more sustainable way to maintain weight loss in the long run.
Crisis of the waistband
Daily calorie recommendations vary based on factors like age and activity level, but most women need at least 1,600 calories to maintain their weight, while men typically require at least 2,000.
Here’s the shocking reality: The average American is chowing down more than 3,800 calories a day — much of it from processed foods, refined grains and added sugars, according to the US Department of Agriculture.
The Centers for Disease Control and Prevention paints an even grimmer picture, revealing that more than 2 in 5 US adults are obese, along with about 1 in 5 children.
The obesity epidemic is fueling a spike in chronic conditions, including high blood pressure, Type 2 diabetes, heart disease, stroke and certain cancers.
4:3 fasting vs. daily calorie restrictions
Researchers from the University of Colorado School of Medicine enlisted 165 overweight or obese adults for the study, published Monday in the journal Annals of Internal Medicine.
Participants were randomly assigned a 4:3 intermittent fasting regimen or a traditional daily calorie restriction plan for one year.
On three nonconsecutive days each week, the intermittent fasting group was asked to cut its calorie intake by 80% of what it needed to maintain weight.
On the other four days, these participants could eat their normal diet, with no restrictions or calorie counting, but with an emphasis on healthy foods and portion control.
Meanwhile, the calorie restriction group had to reduce its daily calories by a third.
Both groups participated in a comprehensive lifestyle program aimed at fostering behavioral change. This included setting exercise goals, attending group meetings led by dietitians and receiving personalized support.
After 12 months, participants in the 4:3 fasting group lost an average of 7.6% of their body weight — around 17 pounds — compared to just a 5% loss in the calorie restriction group.
Additionally, 58% of those in the fasting group achieved at least a 5% weight loss, compared to 47% in the calorie restriction group. Dropout rates were also lower for the 4:3 group at 19% versus 30% in the calorie restriction group.
A ‘sweet spot’ for fasting
“It was surprising and exciting to me that it was better,” said Dr. Victoria Catenacci, co-lead study author and an associate professor of endocrinology at the University of Colorado School of Medicine.
She pointed out that previous studies hadn’t shown a significant difference in weight loss between intermittent fasting and daily calorie restriction.
So, why did this study find a notable difference? Danielle Ostendorf, co-lead author and an assistant professor at the University of Tennessee, Knoxville, believes the 4:3 approach hits a “sweet spot” among fasting regimens.
For instance, weight loss wasn’t as significant in studies where participants fasted just two days a week. She explained that this likely didn’t create a large-enough calorie deficit to outperform daily calorie restriction.
Similarly, fasting every other day proved too rigid and hard to stick with long-term.
“With this 4:3 approach, where they’re fasting three days a week (which are flexible and can be worked around a personal schedule), it might be a middle ground where they feel like they can adhere to it, and it’s feasible to implement in their daily lives,” Ostendorf said. “It also produces a significant calorie deficit across the week.”
Catenacci agreed, adding that the 4:3 strategy could be a game-changer for those who’ve struggled with daily calorie counting.
“It’s really hard to restrict calories every day,” she told ABC News. “It’s just another strategy for people to consider.”
More than just weight loss
The benefits of fasting weren’t limited to the scale.
Participants in the fasting group also showed more favorable changes in critical health metrics like systolic blood pressure, total cholesterol, fasting glucose and hemoglobin A1C compared to those on daily calorie restrictions.
“Those were secondary outcomes, so we need a larger study where we’re actually powered to look at those changes to make conclusive declarations on what changes are happening,” Ostendorf noted.
The next steps for research
The findings are promising, but further research is needed to determine if the 4:3 fasting regimen is safe and effective for different populations, including older adults and people with diabetes, cardiovascular disease or cancer.
Catenacci said that researchers just finished a pilot study measuring the 4:3 fasting regimen in 15 women, all Stage 1 to 3 breast cancer survivors who’ve completed their primary treatment.
Ostendorf added that they are also looking to develop a comprehensive program around the 4:3 fasting model that clinics and community programs can offer so more people can access it.
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