Results of the review
Thirteen studies (n=263) were included: 6 crossover randomised controlled trials (RCTs; n=91), 3 parallel-group RCTs (n=96), 1 non-randomised controlled trial (n=17) and 3 before-and-after studies (n=59).
The studies were small and short term. Study settings, participants and interventions varied widely. Participant drop-out rates were high and some primary studies reported that long-term dietary adherence was poor.
An investigation of clinical differences between the studies found no significant relationship between any of the outcomes and participant age, inclusion of participants on insulin, or duration of dietary intervention.