Study backs 5:2 diet for diabetes

Fasting two days out of seven looks to be just as good as dieting every day of the week when it comes to weight loss and glycaemic control in those with type 2 diabetes

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Fasting two days out of seven looks to be just as good as dieting every day of the week when it comes to weight loss and glycaemic control in those with type 2 diabetes. 

The 5:2 diet gained popularity in recent years, thanks to British television journalist and doctor, Dr Michael Mosley, who proposed the intermittent fasting technique could help weight loss, improve blood glucose and blood lipid levels. 

Intermittent calorie restriction, in this case limiting intake to 500 to 600 calories a day for two days a week but eating normally on other days, had been heralded as a beneficial alternative for people who struggle to keep to a strict low calorie diet daily. 

However, to date there was little research on how well it worked for those with type 2 diabetes. To investigate, South Australian researchers took 137 overweight or obese patients with well-controlled diabetes and randomly allocated them to either intermittent fasting group or a 1200 to 1500 calorie daily diet. 

Their non-inferiority trial showed that over the course of a year, participants in both groups lost a significant amount of weight and their HbA1c levels improved. Those with the highest blood glucose levels improved the most across both groups, and intermittent fasters lost an average of 6.8 kgs and those with a daily calorie restriction lost an average of 5 kgs over the year. 

Intermittent energy restriction was “an effective alternative diet strategy” for improving blood glucose for patients with diabetes, the authors said.  

Both groups were given booklets with some meal suggestions and dietary advice, but to keep the situation as close to the real world as possible, the researchers avoided giving the participants meal replacements. 

They noted that compliance to both diets was “excellent” in the first three months, with 90% of those in the continuous energy restriction group and 97% of those in the intermittent group adhering, and that it roughly halved in the following months. 

“Anecdotally, participants in the intermittent energy restriction group reported that although they were not following the protocol consistently after three months, they found that they could use it effectively to prevent weight gain because the energy restriction involved only two days.” 

“Intermittent energy restriction is safe for people who have either diet-controlled type 2 diabetes or are using medication that is not likely to cause hypoglycaemia. 

For people using sulfonylureas and/or insulin, intermittent energy restriction requires medication changes and regular monitoring, especially in the initial stages,” the authors cautioned. 

JAMA Network Open 2018; online 20 July