intermittent fasting weight lossThroughout modern times, people wishing to lose weight will try almost any diet to achieve success. One of the more popular in recent memory is intermittent fasting for weight loss—the idea of fasting one day (or for part of one day), combined with eating slightly more calories the next. While fad dietitians, bloggers, and Facebook posts have been claiming for months that intermittent diets work, there hadn’t been a scientific study on its benefits.

A new study from the University of Illinois at Chicago was published recently in JAMA Internal Medicine. The study followed 100 obese people for a year, making it the largest and longest study to study alternate-day fasting to date. With the preliminary results of this study, we can better understand the effects of intermittent fasting vs. traditional dieting.

The Study

In the recent study examining the results of intermittent fasting for weight loss, there were three groups in the 100 people. One was a calorie restricted group (traditional dieting), the second was an alternate-day fasting group, and the third was the control group who were told to maintain their weight.

In the calorie-restricted group, participants followed the traditional approach to weight loss, reducing their calorie intake by 25% split among three daily meals. On the other hand, the intermittent fasting group only ate 25% of their caloric needs on “fast” days, between 12 PM and 2 PM. These fast days were bookended by “feast” days, where they would eat 125% of their caloric needs, split between three meals. For a 2000 calorie diet, they’d eat 500 calories on a fast day and 2500 calories on a feast day.

In the control group, people ate the way they normally would and were instructed to maintain their weight as best they could.

To find out if intermittent fasting works long-term, the participants were told to maintain their weight loss for another six months. The fasting group ate half their caloric needs on fast days during this period and 150% on feast days, while the calorie restricting group ate 100% of their caloric needs.

The Results

So, does intermittent fasting work for weight loss? The study found that after the year of weight loss and maintenance, there was no significant difference in weight loss between the caloric restriction and intermittent fasting group. Neither group experience higher risk for health issues either, such as cardiovascular issues.

However, the major difference between the two groups was in the success in the sustainability of the plans. 38% of people dropped out of the fasting group, compared to only 29% of calorie restricting group by the end of the year. Furthermore, people in the fasting group starting the move toward daily calorie restriction versus intermittent fasting—signaling that while intermittent diets may have short-term effects, it’s difficult to stick with them over the long run.

Both groups lost a similar amount of weight, 6% body weight for the alternate-day fasting group, 5.3% for the calorie restricting group, meaning there was no statistically significant difference between the two.


The key to a successful weight loss plan is a diet and exercise plan you can stick to long-term. The experts at Diet Doc can help you plan a calorie-restricted diet with food you still love eating, alongside an exercise plan and medical weight loss advice that works for your situation. Get in touch with Diet Doc to speak to one of our experts about your weight loss possibilities today.