4:3 intermittent fasting beats calorie counting for weight loss

In the search for sustainable weight loss, one diet strategy is starting to stand out from the rest. A new yearlong clinical trial has found that a popular form of intermittent fasting—called the 4:3 method—leads to greater weight loss and better health outcomes compared to traditional daily calorie restriction.

The study, published in the Annals of Internal Medicine, reveals that this approach may not only be easier to stick with, but also more effective in helping people with excess weight shed pounds.

The trial was led by researchers at University of Colorado School of Medicine and included 165 adults with overweight or obesity. Participants were randomly assigned to one of two diet plans: the 4:3 intermittent fasting (IMF) method or daily caloric restriction (DCR). Both groups were supported with gym memberships, group meetings with dietitians, and clear goals for healthy eating and exercise.

The goal of the 4:3 plan was to reduce energy intake by 80% on three nonconsecutive days each week. On the other four days, participants ate normally—but were encouraged to choose healthy foods and avoid overeating. In contrast, the daily calorie group followed a strict plan that cut daily intake by 34%, requiring participants to count calories and follow a diet that included 55% carbs, 15% protein, and 30% fat.

By the end of 12 months, participants in the 4:3 group had lost an average of 7.6% of their body weight, compared to a 5% loss in the DCR group. That difference may seem modest, but it had important health effects.

Weight loss wasn’t the only benefit seen with the intermittent fasting group. Participants following the 4:3 plan also showed better results in several key health markers. These included lower systolic blood pressure, improved fasting glucose levels, and reductions in both total and “bad” LDL cholesterol. These are important risk factors for heart disease and diabetes.

Victoria Catenacci, MD, one of the study's lead authors and a specialist in obesity medicine, said the findings were both surprising and hopeful. “It was exciting to see that this method led to better outcomes,” she explained. “This is a strategy backed by evidence, especially for people who find daily calorie counting hard to stick with.”

Her co-lead author, Dr. Danielle Ostendorf, agreed. Now a researcher at the University of Tennessee Knoxville, she emphasized the value of this method for real-world use. “The 4:3 approach might be the sweet spot,” she said. “It's flexible enough for people to live their normal lives but strict enough to create a real calorie deficit.”

The study stands out because it matched the calorie deficit between both groups—something most similar studies haven't done. Whether participants restricted calories three days a week or every day, they were expected to cut their weekly intake by roughly 34%.

That made the results even more meaningful. Previous studies using other fasting methods—like the 5:2 plan (fasting two days per week) or alternate-day fasting—didn’t show better weight loss than traditional diets. But this time was different.

Dr. Ostendorf explained why 4:3 might hit the right balance. “Two fast days a week might not be enough to cause big weight changes,” she said. “But fasting every other day can be too hard. With 4:3, it’s flexible and easier to follow over time.”

The numbers support her view. While 47% of people in the calorie-counting group reached the 5% weight loss target considered clinically meaningful, 58% of the fasting group hit that goal. That’s a big deal when you consider the long-term health benefits tied to just a 5% drop in weight.

One of the biggest surprises in the study was that people in the 4:3 fasting group not only ate fewer calories, they also stuck with the program longer. Using a scientific method called the doubly labeled water technique, the researchers tracked actual calorie intake based on how participants’ bodies processed hydrogen and oxygen isotopes.

The results showed that the 4:3 group followed the diet more closely than those in the DCR group, despite having the same target energy deficit. That translated into lower dropout rates: only 19% of the fasting group quit the study by the one-year mark, compared to 30% of the DCR group.

Dr. Catenacci explained why that may be. “With fasting, you don’t have to think about food every day,” she said. “That may help people feel less overwhelmed.”

The plan also made room for personal flexibility. Participants could pick which three days to fast each week, adjusting around work or social plans. On those days, women aimed for 400–600 calories and men for 500–700, depending on body size. On regular eating days, there were no set limits—but a strong push toward healthy meals and portion control.

Both groups had access to group-based coaching sessions led by registered dietitians. For the first 12 weeks, they met weekly. After that, the meetings were held every other week. Participants also received a free gym membership and were encouraged to exercise for 300 minutes per week.

These behavioral components played a major role in the study’s success. “The support gave participants accountability and structure,” said Dr. Ostendorf. “That aligns with current clinical guidelines for obesity treatment.”

By combining the 4:3 fasting model with community support, fitness tools, and expert guidance, the research team created an environment that helped participants stick with their goals.

The researchers are not stopping here. They are now studying how 4:3 fasting might benefit specific groups—like breast cancer survivors, older adults, and people with chronic conditions such as diabetes and heart disease. A pilot program with 15 breast cancer survivors has already been completed, and a new phase is starting soon.

They're also digging deeper into the biology behind the benefits. Stool and blood samples were collected from participants to explore changes in the gut microbiome and hormones related to hunger and metabolism. These results could help explain why the 4:3 plan works better for some people.

“We believe these fasting periods may offer other metabolic advantages,” said Dr. Ostendorf. “We’re still analyzing those findings, but we suspect that adherence plays a major role.”

Dr. Catenacci added that they’re seeking long-term funding to see how the 4:3 method holds up beyond one year. “Twelve months is great, but we want to know what happens over two or three years,” she said.

Right now, there’s no widely available clinic or community program that offers a structured 4:3 intermittent fasting plan. That’s something Dr. Ostendorf hopes to change.

“We’ve had people asking how they can try this,” she said. “So now we’re thinking about how to design a low-cost program that could be offered in local clinics or online.”

Their vision includes making the plan easy to follow, supported by education and tools that empower people to take charge of their own health. If future research continues to support the benefits of 4:3 intermittent fasting, this approach could soon be part of standard care for weight loss.

Note: The article above provided above by The Brighter Side of News.

Like these kind of feel good stories? Get The Brighter Side of News' newsletter.