Scientists Find Intermittent Fasting Better for Weight Loss Than Calorie Counting
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New research suggests the 4:3 intermittent fasting schedule is better than calorie restriction for weight loss.
Previous studies found that intermittent fasting and calorie restriction had similar weight loss results.
Experts point out that this is a restrictive eating plan, making it hard to stick with over time.
While some people swear by intermittent fasting for weight loss, recent research has found that it usually leads to results that are similar to calorie counting. But a new study suggests that the type of intermittent fasting you do matters—and a certain style of the eating plan could have an edge over calorie counting for weight loss.
The small study is raising a lot of questions about which method to choose, plus why one type of intermittent fasting may lead to better results. But experts stress that this doesn’t mean everyone should suddenly follow an intermittent fasting eating plan to lose weight.
Meet the experts: Mir Ali, M.D., medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA; study co-author Victoria A. Catenacci, M.D., associate professor in the University of Colorado Anschutz Medical Campus and medical director of the CU Medicine Weight Management and Wellness Clinic; Jessica Cording, R.D., C.D.N., author of The Little Book of Game-Changers; Scott Keatley, R.D., co-owner of Keatley Medical Nutrition Therapy; Keri Gans, R.D.N., author of The Small Change Diet; Sharon Puello, R.D., a nutritionist at NYC Health + Hospitals/Jacobi
Here’s what the study found, plus what it suggests about intermittent fasting going forward.
What did the study find?
The study, which was published in the Annals of Internal Medicine, split 125 people with overweight or obesity into two groups. One group followed a calorie-restricted diet with a goal of reducing their calories by 34.3%, while the others followed a 4:3 intermittent fasting diet. (In case you’re not familiar with it, a 4:3 diet is when you have four days each week of eating whatever you want and three non-consecutive days where you fast.)
People in the 4:3 group weren’t asked to restrict their calories on eating days, but they were encouraged to make healthy food choices. On fasting days, they cut their daily calorie intake by about 80%.
All of the participants were given free gym memberships and asked to exercise for at least 300 minutes a week. Everyone lost weight after 12 months, but the intermittent fasting group lost more—7.6% of their body weight compared to 5% in the calorie-restricted group.
As a result, the researchers concluded that a 4:3 intermittent fasting plan leads to “modestly greater weight loss” in people with overweight or obesity.
Why might a 4:3 intermittent fasting diet be better for weight loss?
The researchers didn’t explore why the 4:3 diet was better for weight loss, but there are some theories.
One is that this eating pattern doesn’t require a person to be hyper-focused on their diet every single day. “Doing something every single day is hard—it takes a lot of attention and focus, and it is easy to get derailed and frustrated if you have a bad day or two,” says study co-author Victoria A. Catenacci, M.D., associate professor in the University of Colorado Anschutz Medical Campus and medical director of the CU Medicine Weight Management and Wellness Clinic. “We think that it is easier to stick to a diet where you restrict significantly a few days a week than it is to stick to a diet where you have to restrict modestly every single day.”
The 80% calorie restriction on fasting days is also pretty steep, points out Jessica Cording, R.D., C.D.N., author of The Little Book of Game-Changers. If someone is doing that and having a healthy diet on eating days, she says it makes sense that they would lose weight.
“The 4:3 diet creates a clear caloric deficit over the course of the week. That’s the mechanism,” agrees Scott Keatley, R.D., co-owner of Keatley Medical Nutrition Therapy.
“But it’s not just about the numbers: intermittent fasting may also impact insulin sensitivity, fat oxidation, and gut hormone regulation.” The 4:3 approach may also help to limit mindless snacking and get rid of the daily burden to count every calorie, he says.
It can even help people make healthier choices, according to Sharon Puello, R.D., a nutritionist at NYC Health + Hospitals/Jacobi. “Many individuals who follow an intermittent fasting pattern find that on their fasting days they tend to prioritize healthier eating, as it changes how they look at food from a mindset of pleasure to a mindset of nourishment,” she says. “Individuals can also end up developing healthier coping mechanisms, as they look to exercise or other outlets to expend their energy during fasting periods, when they otherwise ordinarily would have turned to food.”
Dr. Catenacci points out that people in the study worked their way up to the 4:3 style of intermittent fasting, starting with one fast day a week in the first week, before moving up to two the second week, and three the third week. “Some people loved it right away and some people found it difficult initially,” she says. “It does get easier over time.”
What does other research say about intermittent fasting for weight loss?
Intermittent fasting has been studied in the past for weight loss, but a lot of the research focuses on a type of eating plan known as 16:8. Under this schedule, you fast for 16 hours and then have an eating window of eight hours.
A small study published in Annals of Internal Medicine in 2023 followed 77 people with obesity and found that those who followed a 16:8 eating plan lost slightly less weight than participants on a calorie-restricted diet.
And a 2022 study of 139 people with obesity published in The New England Journal of Medicine found that people who followed a 16:8 eating plan and calorie-restricted group lost similar amounts of weight.
What are the drawbacks of a 4:3 intermittent fasting schedule?
A 4:3 intermittent fasting schedule is restrictive, and that’s concerning for many dietitians. “From a mental standpoint, I do not recommend a 4:3 approach,” Cording says. “What is important for wellness is feeling like you can enjoy your life and have healthy patterns that are sustainable.”
While Cording says that some people may feel that a 4:3 approach is fine for them, others may struggle to stick with the pattern of days where they eat very little.
“Any restrictive pattern can backfire long-term if it's not sustainable,” Keatley says. “Hunger, social limitations, and perceived food scarcity can cause people to swing hard in the other direction once the diet ends—or once life stress hits.” That weight regain can also interfere with your metabolism, making it hard to lose weight in the future, he says.
But some people may find that the 4:3 approach works for them. “If they can still meet their overall nutritional needs and tolerate fasting days without experiencing negative side effects, such as fatigue, dizziness, and nausea, the 4:3 diet may be a good fit for them,” says Keri Gans, R.D.N., author of The Small Change Diet. “However, I would strongly recommend consulting with a registered dietitian before initiating this type of plan.”
Cording also stresses that people may not lose as much weight on a 4:3 diet under a normal, non-research setting. “There’s research and then there’s real life,” she says. “A weight loss strategy in a research setting is very different from what may be truly effective and sustainable in real life.”
The best way to lose weight, according to experts
Weight loss comes down to a calorie deficit, points out Mir Ali, M.D., medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA. Meaning, you burn more calories than you take in.
“You can do that intermittently, but everybody is different,” Dr. Ali says. “For some people, being in a calorie deficit every day is the most beneficial way to lose weight. For others, it’s intermittent fasting.”
Cording agrees that the right dietary approach is individual. “I always encourage people to look at what might be out of balance and contributing to issues with weight management and starting there,” she says.
However, she says that making sure you’re having balanced meals and snacks with a mix of fiber, fat, protein, and non-starchy vegetables can go a long way toward helping you to feel full.
Ultimately, if you want to lose weight and are torn between different methods, Cording recommends asking yourself this: “How will it impact my quality of life, physically and emotionally?” The option that will be the least disruptive is usually the best, she says.
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