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A new study found that intermittent fasting could help people with type 2 diabetes lose weight and lower blood sugar levels. FG Trade/Getty Images
  • A study compared 5:2 intermittent fasting, done with meal replacements, to diabetes medications for the treatment of type 2 diabetes.
  • People who did intermittent fasting lost more weight and saw greater improvement in blood glucose control.
  • The 5:2 intermittent fasting diet involves eating 25% of your usual calories on two nonconsecutive days each week, and eating regularly the rest of the week.

A new study finds that intermittent fasting with low-calorie meal replacements may be an effective way for people with type 2 diabetes to lose weight and control blood sugar levels, compared to standard diabetes medication.

For people with type 2 diabetes, especially those with a recent diagnosis, losing weight may help improve their blood glucose (sugar) levels and reduce the need for diabetes drugs such as metformin.

However, maintaining weight loss with diet alone can be challenging.

In the new study, researchers found that combining these two dietary interventions may make it easier.

The study was published June 21 inJAMA Network Open.

Researchers found that people recently diagnosed with type 2 diabetes who did intermittent fasting using meal replacements lost more weight over 16 weeks compared to people who received standard diabetes medication.

Those who did intermittent fasting also saw greater improvements in their hemoglobin A1c (HbA1c or A1C) levels, a measure of blood glucose control.

Michael J. Wilkinson, MD, a cardiologist and assistant professor of medicine at UC San Diego Health, said the results seen in the study with intermittent fasting and meal replacements were impressive.

However, he pointed out that this was not simply a study of intermittent fasting. On the two fasting days per week, participants consumed a lower-calorie meal replacement, which ensured they ate fewer calories.

“The content of what was supplied in those meal replacements is important to the results,” said Wilkinson, as is the nutrition and exercise counseling that all participants received throughout the study. This combination of [approaches] may explain why people saw greater changes in weight and HbA1c compared to other studies, he said.

The new study included 405 adults in China who were overweight or had obesity and were recently diagnosed with type 2 diabetes. Almost two-thirds of participants were men, the average age was 46 years old and the average HbA1c level was 7.9%.

An HbA1c level of 6.5% or higher is in the diabetes range. Most people with diabetes aim to keep their HbA1c below 7%.

Researchers randomly assigned participants to be treated with a diabetes medication — either metformin (Glucophage) or empagliflozin (Jardiance) — or to follow an intermittent fasting plan for 16 weeks. Overall, 332 people completed the 16-week treatment.

All participants received guidance every 4 weeks from nutritionists and research staff about eating healthy and exercising regularly.

Researchers continued to monitor participants for 8 weeks after the treatment period. This included measuring HbA1c, body weight, waist and hip circumference, blood pressure and other metabolic markers.

People assigned to the intermittent fasting plan fasted for two nonconsecutive days per week, and mostly ate their usual foods and amounts on the other days — what’s known as 5:2 intermittent fasting.

To control the amount of calories and nutrients that people ate on fasting days, researchers provided participants with prepackaged meal replacements. People ate about one-quarter of their usual calories on those days — 500 calories for women and 600 calories for men.

Vicky Pavlou, RDN, a registered dietitian and doctoral student at the University of Illinois Chicago told Healthline that the approach used in the study is not a “true” 5:2 intermittent fasting diet.

Participants also ate a meal replacement for dinner on their non-fasting days and were asked to count their calories. Usually, people are allowed to eat whatever they want on non-fasting days, she said, which is simpler and easier to stick with.

“In general, the point of intermittent fasting is to give people really simple instructions,” she said, “as an alternative to counting their calories, which can be burdensome for people.”

Researchers found that after 16 weeks, people following the intermittent fasting diet had greater improvements in certain measures.

People who did intermittent fasting lost an average of 21 pounds over 16 weeks, versus 12 to 13 pounds for those receiving one of the diabetes medications.

The intermittent fasting group also saw significant reductions in waist and hip circumference and systolic and diastolic blood pressure.

In addition, in the intermittent fasting group, HbA1c decreased by 1.9%, compared to a decrease of 1.6% in the metformin group and a decrease of 1.5% in the empagliflozin group.

According to the American Diabetes Association, people with type 2 diabetes who maintain an HbA1c of 6.5% or lower for at least 3 months are considered to be in diabetes remission.

In the new study, 80% of people in the intermittent fasting group met this target at the end of 16 weeks, with 77% still at that level after the 8-week follow-up. A longer follow-up would be needed in order to confirm that they met the American Diabetes Association’s definition of remission.

Wilkinson said one of the strengths of the study is its duration, although he thinks additional studies are needed with an even longer follow-up.

“With drugs like metformin and empagliflozin, the expectation is that these are long-term, maybe lifetime, therapies,” he said. “So if we’re comparing those to 5:2 intermittent fasting with meal replacement, the expectation is that it’s a long-term intervention.”

For that to work, “we need to have a better understanding of the long-term adherence and also the long-term safety [of intermittent fasting],” he said.

In particular, the meal replacements would need to provide all the necessary vitamins, minerals and other nutrients, he said. Studies might also need to monitor people’s health and body composition — such as lean muscle mass — to see if long-term use of meal replacements is safe, he added.

Pavlou said if you are only replacing one meal with a meal replacement — versus using them for every meal — it is less of a concern that someone would fall short on their nutrients.

In addition, the meal replacements she uses in the clinic are designed to provide a full range of nutrients and to be safe for regular use over several months. Still, people prescribed meal replacements long-term are regularly monitored by their doctor, she said.

Another concern that Wilkinson raised about the new study is that participants were all diagnosed with diabetes within the past year and had not used diabetes medications in the 3 months leading up to the study. So the results may not apply to other groups of patients.

Colette Knight, MD, chair of the Inserra Diabetes Institute at Hackensack University Medical Center echoed some of his concerns.

“This study focuses on the newly diagnosed patient with diabetes — a group where lifestyle intervention can be very helpful,” she told Healthline. “This [approach] is not for the 20-year diabetic patient.”

In addition, “we need to look at a more diverse population of patients with a longer duration of diabetes,” she said.

Also, more studies are needed in order to know “what happens when you add this restrictive diet to known diabetes medications that also promote weight loss,” she said.

Around 11% of Americans have diabetes, with type 2 diabetes accounting for 90-95% of all cases, according to the Centers for Disease Control and Prevention.

Risk factors for type 2 diabetes include being overweight or having obesity, having a family history of type 2 diabetes, being physically inactive, and being older than age 45.

Lifestyle changes such as healthy eating and exercise are recommended for people with type 2 diabetes, even for those who are taking a diabetes medication. Diet and exercise alone, though, may not be enough to help people lower their blood glucose level.

Intermittent fasting, though, is designed to make it easier for people to cut back on calories while still getting enough nutrients in their diet.

“There is some research suggesting that intermittent fasting can be an effective strategy for managing type 2 diabetes and prediabetes,” said Knight. “Some studies have also shown that intermittent fasting can lead to improvements in glycemic control, weight loss and other metabolic parameters in individuals with these conditions.”

Similarly, research shows that including meal replacements as part of a lifestyle intervention, without intermittent fasting, can lead to greater weight loss and decreases in HbA1c, compared to other diets or to diabetes education.

In spite of the benefits seen in the new study and past research, there is not yet general agreement among doctors about which people might benefit most from intermittent fasting, Knight said. In addition, “just this one approach may not be enough,” she said.

Other types of intermittent fasting and time-restricted eating methods are also available, which gives people more options. These include:

  • 16/8 time-restricted eating: This involves fasting for 16 hours each day and restricting eating to an 8-hour window.
  • Eat Stop Eat: This involves fasting for 24 hours once or twice a week.

“Each has its own advantages and disadvantages,” said Knight. “The best approach for individuals with diabetes depends on their individual preferences, lifestyle and health status.”

Knight recommends that people with diabetes talk to their doctor before starting any intermittent fasting regimen, to ensure it is safe and appropriate for their specific needs.

Researchers randomly assigned people recently diagnosed with type 2 diabetes to 16 weeks of treatment with a diabetes medication or intermittent fasting with meal replacements.

Those in the intermittent fasting group saw greater improvements in their hemoglobin A1c, a measure of blood glucose control, and weight loss, compared to the diabetes medication groups.

Experts say additional research is needed, with longer follow-up and a more diverse population. This includes testing intermittent fasting in people who have had diabetes longer and those taking diabetes medications.