Low calorie vs low carbohydrate for Type 2 Diabetes remission (DiRECT vs Virta) – Dr Glen Davis

Executive Summary

* There are two dietary ways to put type 2 diabetes (T2D) into remission – transient very low calorie and sustained very low carbohydrate. The DiRECT study presents the evidence for the former, whereas the Virta study presents the evidence for the latter.

* Both studies involved similar numbers of people (300 DiRECT/ 350 Virta). They had some differences in exclusions and baseline measures, which are detailed in this note.

* Results are available for DiRECT and Virta after one year and two years enabling comparison. The primary outcomes differed slightly but both involved weight loss and reduced HbA1c.

* DiRECT researchers stress that their study was randomised whereas Virta wasn’t. Upon examination it transpired that neither study was randomised to the individual (DiRECT was randomised by practice, and Virta was assigned by practice). In both cases, patients knew whether they would be offered the intervention or control before agreeing to participate.

* Comparing the two studies by protocol, Virta included more complex patients and patients who had had T2D almost three times longer than DiRECT patients. Virta also differed from DiRECT by using real food consumed to satiety vs soups and shakes composed of purified nutrients that required severe calorie restriction for months at a time.

* Comparing the two studies by results, the reductions in HbA1c were greater for Virta at one and two years. Both absolute (kg) weight loss and relative (%) weight loss were higher for Virta at one and two years. Virta had better retention/ongoing participation at one year, whereas DiRECT did at two years.

* The results were strongly in favour of Virta to the extent that I concluded not only should a low carb diet be offered as an alternative to every patient who is offered a severe calorie restricted diet such as DiRECT; but the above comparison of results should also be shared with patients.


*As noted in Dr Glen Davies presentations at the GP CME Conference in June 2020