Following a very-low-calorie diet on some days of the week may lead to improved blood glucose control in overweight or obese adults with type 2 diabetes, according to a study published in the Journal of Diabetes Investigation.
Very few previously published studies have looked at the effects of different types of intermittent low-calorie diets in people with diabetes, the study authors noted. Following a very-low-calorie diet on some days may have a number of different potential benefits for people with diabetes and excess body weight — including weight loss, improved blood glucose control, and improved blood markers related to cardiovascular disease (such as blood pressure and cholesterol and triglyceride levels). The goal of this study was to look at any differences in outcomes from following different protocols for intermittent very-low-calorie diets.
A total of 40 participants took part in the study. Their average body-mass index (BMI, a measure of body weight that takes height into account) was 30.1, which just barely falls in the “obese” category, above “overweight.” All participants had type 2 diabetes and were between 30 and 60 years old. Their average A1C level (a measure of long-term blood glucose control) at the beginning of the study was 7.4%, indicating that most people weren’t meeting recommended blood glucose targets. Participants were randomly assigned to one of three study groups. One group followed a very-low-calorie diet two days per week, one did so four days per week, and the third group served as a control that didn’t make any dietary changes. In the very-low-calorie diet groups, participants received a 600-calorie diet to eat on their restricted days, and were told to eat as much as they liked on the other days.
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Intermittent low-calorie diets linked to various health benefits
There were several notable differences seen between the study groups over the course of 20 weeks. Both very-low-calorie diet groups had improved blood glucose control, starting two weeks into the study and continuing through the entire study period. After 10 weeks, the control group had an average A1C level of 6.7% and an average fasting glucose level of 140.6 mg/dl. The two-days-per-week diet group had an average A1C level of 6.7% and an average fasting glucose level of 134.3 mg/dl, while the four-days-per-week diet group had an average A1C level of 6.4% and an average fasting glucose level of 107.9 mg/dl. These numbers show that the four-days-per-week diet group had glucose measurements falling below the levels indicating the presence of diabetes.
After 20 weeks, much of the improvement seen in the diet groups at 10 weeks was sustained. The control group had an average A1C level of 6.9% and an average fasting glucose level of 137.2 mg/dl. The two-days-per-week diet group had an average A1C level of 6.8% and an average fasting glucose level of 130.8 mg/dl, while the four-days-per-week diet group had an average A1C level of 6.4% and an average fasting glucose level of 119.9 mg/dl. At this point, 29% of participants in both of the diet groups met the criteria for diabetes remission, meaning that they had normal glucose levels without taking any diabetes medications. In the control group, 0% of participants met the criteria for diabetes remission.
The two diet groups also saw improvements in triglyceride levels, body weight and BMI, and body fat mass over the course of the study — indicating that this mode of calorie restriction may also reduce the risk for cardiovascular disease. Importantly, no serious adverse events were seen in any of the study groups, indicating that following a very-low-calorie diet on some days of the week appears to be safe for people with type 2 diabetes and excess body weight.
The researchers concluded that following a very-low-calorie diet on some days of the week was “highly effective in achieving optimal glycemic control” among study participants, and that doing so two days or four days per week led to fairly similar results. While more studies on this type of diet are needed, the study authors noted that “this modality of treatment might have great clinical implications for patients with type 2 diabetes and obesity.”
Want to learn more about intermittent fasting? Read “Intermittent Fasting: Not So Fast” and “Intermittent Fasting May Improve Blood Sugar Without Weight Loss: Study.”
