At a glance
- People with obesity and type 2 diabetes lost more weight by fasting daily than by attempting calorie restriction over a six-month period.
- Blood sugar levels in both groups of people decreased, and no serious side effects were observed.
About 1 in 10 Americans has type 2 diabetes, a disease in which blood sugar levels are too high. Diabetes can lead to serious health problems such as heart disease, nerve damage, and eye problems.
Excess weight is a major risk factor for developing type 2 diabetes, and weight loss is often recommended for people with excess weight and type 2 diabetes. Calorie restriction, which reduces total calorie intake, is a mainstay of most weight loss programs. However, it is very difficult to continue such therapy over a long period of time.
Time-restricted eating, also known as intermittent fasting, is emerging as an alternative weight loss paradigm. This approach limits the times when you can eat food, but not the amount or type of food. A small study suggests that intermittent fasting is safe and promotes weight loss in people with type 2 diabetes. However, these studies only followed participants for a short period of time. They also did not compare this approach to traditional calorie restriction.
In a new clinical trial, an NIH-funded research team led by Dr. Krista Varady of the University of Illinois at Chicago compared fasting to calorie restriction in terms of weight loss and lowering blood sugar levels. They recruited 75 people with obesity and type 2 diabetes. Of those, 70 were Hispanic or non-Hispanic black, two groups with the highest prevalence of diabetes in the United States. Participants were randomly assigned to one of three dietary groups for six months.
The fasting group could eat whatever they wanted, but only between noon and 8 p.m. The second group worked with a nutritionist to reduce the number of calories needed to maintain weight by 25%. The control group did not change their diet at all. All groups received education about healthy food choices and closely monitored their blood sugar levels during the study. The results will be announced on October 27, 2023. JAMA network open.
After six months, participants in the fasting group lost an average of 3.6% in weight compared to the control group. In contrast, people in the calorie restriction group did not lose significantly more weight than the control group.
Both groups had similarly healthy declines in average blood sugar levels. Waist circumference also decreased in both cases. No serious side effects, such as blood sugar levels falling outside safe limits, were observed in either treatment group. People in the fasting group reported that the diet was easier to adhere to than the calorie restriction.
“Our research shows that time-restricted eating may be an effective alternative to traditional eating for people who can’t eat it or are burned out from it. “This shows that,” Varady says. “For many people trying to lose weight, counting time is easier than counting calories.”
Some medications used to treat type 2 diabetes must be adjusted to time-restricted meals. Therefore, anyone considering intermittent fasting should consult a doctor before changing their eating pattern.
—Written by Sharon Reynolds
Funding: NIH’s National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). University of Illinois.
