In follow up to my recent post on intermittent fasting, the first study of long term intermittent fasting in people with type 2 diabetes has now been published.

The study, published online by the JAMA Network Open, randomized 137 adults with type 2 diabetes to eat following one of two patterns for a year:

  •  intermittent fasting: 500-600kcal per day for 2 nonconsecutive days each week, vs
  • continuous energy restricted diet: 1200-1500 kcal per day every day

They found that the two diets were similar in their ability to improve diabetes control, as measured by hemoglobin A1C, which decreased by -0.3% in the intermittent fasting group, and -0.5% in the continuous dieting group (statistically no significant difference).

Weight loss was NOT significantly different between the two groups (-6.8kg in the intermittent fasting group vs -5.0kg in continuous dieting group), though the authors speculate that the difference may have been significant, had the trial enrolled more participants.  Adherence to the study diets was poor in both groups at 1 year (as is typical of most dietary interventions), with only 44% of people sticking to the intermittent fasting program and 49% sticking to the daily dieting program.

So, this study suggests that intermittent fasting, here defined as eating 500-600 kcal per day for 2 nonconsecutive days per week, may be a reasonable approach for people with type 2 diabetes, and comparable to the effects of daily calorie restriction.  In the real world, some people may do well with this modified intermittent fasting pattern, whereas others may prefer to have the same approach each day.  Remember that what works best for one person may not work for the next.

HOWEVER – VERY IMPORTANT POINT:  Some medications for type 2 diabetes need to be adjusted proactively (i.e. before the new eating pattern starts) for days of lower calorie intake, to avoid low blood sugars (hypoglycaemia).  This includes insulin, and oral medications called sulfonylureas (examples include gliclazide (Diamicron) and glyburide) and meglitinides (eg repaglinide (Gluconorm)).  This study had a protocol in place for medication adjustments to proactively avoid low blood sugars, which they ended up having to modify further part way through the trial, as they were still seeing low blood sugars.

So, if you are considering an intermittent fasting eating plan and are taking any of those groups of medications or insulin, be sure to discuss medication adjustments with your health care provider beforehand. 

For people taking SGLT2 inhibitors (canagliflozin (Jardiance), dapagliflozin (Forxiga), empagliflozin (Jardiance)), it is also especially important to stay well hydrated on all days, as these medications cause a loss of water in urine.

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