What Works in Type 2 Diabetes: Intermittent Fasting or Calorie Restriction or Both?

Dear Editor, We read with interest the scoping review titled “A Scoping Review of the Effect of Intermittent Fasting on Diabetes Regulation and Weight Control.”[1] This review is essential in the light of the prevailing obesity pandemic. The authors have correctly identified inconsistencies in the study results using intermittent fasting. While the reported factors, including study designs, demographic variety, and protocols employed in intermittent fasting, may contribute, another significant influence is the calorie restriction associated with intermittent fasting. If intermittent fasting is not combined with calorie restriction and includes binge eating in the food window, the results may be unfavourable. Calorie restriction due to limited eating periods has been presumed to be one of the key drivers of the beneficial effects. A recent meta-analysis indicated that intermittent fasting may serve as an effective alternative to calorie restriction but is not superior to it.[2] A pivotal study demonstrated that, in individuals with obesity, a time-restricted eating plan did not yield greater benefits in reducing body weight, body fat, or metabolic risk factors than daily calorie restriction.[3] The authors rightly note that intermittent fasting may pose difficulties for people on sulfonylureas or insulin. However, prescribing intermittent fasting with prior dose reduction of insulin or sulfonylureas and stringent supervision may avoid hypoglycaemia. Results from the INTERFAST-2 study indicate that individuals with insulin-treated type 2 diabetes mellitus who maintained intermittent fasting from baseline to 2 years achieved a median weight loss of 4.5 kg, compared with 3.1 kg among those who discontinued intermittent fasting. Furthermore, individuals who continued intermittent fasting had median reductions in HbA1c and daily insulin dosage over 2 years, in contrast to those who discontinued, though the results did not reach statistical significance. Notably, no severe hypoglycaemic incidents necessitating third-party assistance or hospitalisation were recorded by any trial participants over the 2-year follow-up period.[4] As obesity specialists, it is essential to educate our care-seekers about the importance of calorie restriction in combination with intermittent fasting for optimal results. It is crucial to carefully adjust glucose-lowering medications in type 2 diabetes that carry a risk of hypoglycaemia so that individuals can undertake intermittent fasting safely, without triggering hypoglycaemic episodes. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.