Intermittent Fasting vs. Calorie Counting for Type 2 Diabetes

3 min read

July 25, 2023 – Losing weight is an important part of type 2 diabetes care – it could help lower blood sugar and reduce the need for some diabetes drugs. To shed the extra pounds, new research shared on Monday shows that intermittent fasting is an effective way to cut calories for people with type 2 diabetes

Intermittent fasting refers to eating only within a limited time window. In this study, featured at the annual conference of the American Society of Nutrition, patients assigned to that group could only eat between noon and 8 p.m. each day – a practice also called time-restricted eating – with a 1-hour grace period. The people in the calorie restriction group were asked to cut their calories by 25%, and a control group continued eating as normal.

In total, the results included 57 overweight and obese people with type 2 diabetes who were randomly assigned to each of these groups. 

After 6 months, those in the intermittent fasting group lost about 4.3% of their body weight – equal to about 10 pounds of weight loss for a person weighing 230 pounds – and people in the calorie restriction group lost about 2.5% of their body weight.

Statistical analysis showed no significant difference between the two groups for weight loss, meaning one method of dieting isn’t necessarily better than the other. 

"Let's not think of this as an approach that's better than calorie restriction," said William Yancy, MD, an internist and weight management specialist at Duke Lifestyle and Weight Management Center in Durham, NC. "It's an alternative approach to calorie restriction."

The reason for the small percentage difference could be because calorie restriction diets tend to be harder to follow, and people have probably tried to cut calories before, according to study author Vasiliki Pavlou, a registered dietitian nutritionist in the Chicago area. 

"People that have type 2 diabetes, they've already been to the doctor, they've already been told to count calories," said Pavlou, a doctoral student at the University of Illinois Chicago. There were many weeks, she said, when people in the study did not track their eating as required, and “we'd have to encourage them to start tracking again."

Sticking to the diet seemed to be more of a problem for the calorie restriction group – about a third didn’t stay within 200 calories of the goal, according to Pavlou. The intermittent fasting group reported that they stuck to the diet 6 out of the 7 days of the week. 

That meant the fasting group cut about 100 calories more per day than the calorie restriction group, which was reflected in their weight loss, Pavlou said.

A1c levels – the measure of a person’s average blood sugar level over time – dropped by about 1% in both the intermittent fasting and calorie restriction groups. 

Up to 90% of people with type 2 diabetes are overweight or obese, and losing weight is an important part of care. Studies have shown that even a 5% reduction in body weight can reduce blood sugar, and type 2 diabetes remission can occur after a 10% loss in body weight – but it depends on the person. 

"It depends on the individual, their metabolic situation, how long they've had diabetes, what kind of approach they're following, maybe what medicines they're taking," Yancy said. "There's a lot of different factors involved in remission."

Intermittent fasting could work well for the right person – but it depends on a person's eating habits and whether their meals usually fall outside the time-restricted window, or it could depend on how well a person follows rules, according to Yancy.

"Some people might not eat much after 8 o'clock, and some people might skip breakfast," he said. "And if that's the case, then it's not going to make a big impact on their weight, probably."

The people in the study generally had advanced type 2 diabetes and were taking a mix of medications, so the results might not apply to people with a more recent type 2 diabetes diagnosis. 

Considering the effect of the diet on medications is also important. Not eating can be dangerous for patients taking short-acting insulin or sulfonylureas, Yancy said.

These findings show intermittent fasting is another option for patients with type 2 diabetes who are trying to lose weight. "If you've tried calorie counting, that's not working for you or if you're kind of burnt out, this is something else that you could try," he said.