The authors of the new study recruited adults with Type 2 diabetes and then split them into three groups. In the first two groups, participants were assigned to take either metformin or empagliflozin. In the third group, participants were taught to follow the 5:2 diet. Women consumed just 500 calories on each of their two weekly fasting days, while men consumed no more than 600 calories - equivalent to about a quarter of their usual caloric intake.

On their fasting days, the participants consumed sparse amounts of food: An egg for breakfast, a couple servings of fruit or vegetables for lunch, and a light salad for dinner. Each meal was paired with a low-calorie meal replacement drink that contained healthy fats, protein, vitamins, minerals and other nutrients. On their non-fasting days, the participants would eat normally for breakfast and lunch and then have a light dinner with a meal-replacement drink.

Significant and sustained improvements

In addition to losing weight, the fasting group saw their HbA1c, a long-term measure of their blood sugar levels, drop 1.9 per cent - significantly more than the groups taking medication. About 80 per cent of participants in the fasting group saw their HbA1c fall below 6.5 per cent, the cutoff for diabetes, compared to 60 per cent of the participants on metformin and 55 per cent of the people taking empagliflozin.

Eight weeks after the study ended, the researchers followed up with the participants and found that most of the people in the fasting group had maintained blood sugar levels below the threshold for diabetes, suggesting that the diet “significantly and sustainably improves HbA1c levels,” the authors wrote.

The researchers found that the fasting group also had greater reductions in their waist circumference, blood pressure levels and triglycerides, a type of fat that circulates in the blood, compared with the participants taking medication.

The researchers cautioned that more studies were needed to examine the long-term effectiveness of the 5:2 diet with meal replacements for Type 2 diabetes. But they said their findings suggest that the diet might be a good initial lifestyle intervention for people with early-stage diabetes.

Fasting combined with meal replacements

Peterson said the study was large, rigorous and cleverly designed because it essentially combined two dietary interventions - intermittent fasting and meal replacements - that have been shown to help people with diabetes.

Many studies have found that diets that incorporate low-calorie meal-replacement shakes, soups and bars help people lose weight and lower their blood sugar levels. A number of studies have also indicated that the 5:2 diet helps people improve their blood sugar control.

Peterson said that one downside of the 5:2 diet is that people often see impressive results in the first few months, but that after about six months to a year on the diet, “they start falling off.”

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“It does seem to have an advantage in the short term, but in the long term which is a year or more, it doesn’t seem to be better than a standard low-calorie diet,” she added.

She also stressed that more long-term research was needed. But in the meantime, she said that people with newly diagnosed Type 2 diabetes might consider discussing with their doctor whether it is worth trying the 5:2 diet in combination with meal replacement shakes like Optifast, Ensure, Soylent or others.

She noted that while participants in the study did not experience many adverse events on the fasting regimen, about 6 per cent of people on the diet reported symptoms of low-blood sugar, which can potentially be dangerous.

“People should absolutely work with their doctor if they want to try this,” Peterson said. “They shouldn’t try it on their own.”

Washington Post

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