Keto vs Mediterranean diet for T2D

Executive Summary

* This week's note looks at something rare in the field of nutrition – a randomised controlled trial (RCT).

* This RCT involved 40 people (33 completed the trial) in San Francisco with borderline or diagnosed type 2 diabetes (T2D).

* The intervention compared two 12-week diets – both whole food (free from sugar and refined grains) and both low carb. One was a keto diet. The other was a low carb version of the Mediterranean diet.

* The main outcome of interest was HbA1c (a measure of glucose in the blood over the previous 12 weeks) at the end of each diet.

* The study concluded that there was no significant difference between the HbA1c levels at the end of the two diets. That was not the whole story.

* The study was concerned about hypoglycemia (low blood glucose) because of the reduction in carbohydrate. HbA1c lowering meds were stopped during the keto diet and halved during the Mediterranean diet. The two diets performed similarly despite the advantage that this gave the Med diet. Sensitivity analysis showed that when the meds difference was excluded, the keto diet performed better.

* In my view, the main conclusion should have been that two low carb diets both reduced HbA1c by 7-9% and weight by 7-8% in as few as 12 weeks and that this was despite stopping or halving an HbA1c lowering drug.

* Low carb diets should be the first intervention recommended for borderline or diagnosed type 2 diabetes.