Background: Recent interest has emerged regarding the effects of Very Low Calorie Diet (VLCD) in people with type 2 diabetes (T2D). We therefore performed a systematic review to investigate the effects of VLCD on HbA1c, weight and cardiovascular risk profile outcomes as well as its safety and tolerability among people with T2D.
Methods: We conducted searches of Cochrane Database of Systematic Reviews, Centre for reviews and Dissemination databases, Medline, Embase, Pubmed, Web of Science, Web of Knowledge and Turning Research into Practice (TRIP) as well as ongoing trial resources. We included all studies involving VLCD and diabetes published until December 2013. Outcome measures include weight, HbA1c, fasting glucose, fasting insulin, lipid profile, blood pressure, safety and drop out rates.
Results: 17 studies were included in the systematic review. Duration of VLCD duration ranged from 5 days to 6 months and duration of follow up ranged from 8 days to 5 years. The age range was 14 years to 59 years of age. Mean weight loss was 13.2kg, ranging from 4.1 to 24kg. Mean Hba1c reduction was 1.4% (ranging between 0.1 to 3.1% reduction across different studies). Three studies reported a significant reduction in the daily doses of insulin. All studies which reported cardiovascular risk profile showed a significant decrease in total cholesterol, systolic and diastolic blood pressure post VLCD. Apart from two studies, all of the other studies showed that the decrease in blood pressure and total cholesterol was not only present immediately post VLCD, but it was also maintained at follow up. However it is important to note that the follow up periods did differ between studies. Overall, drop out rates ranged from 4.7% to 33% and appeared to be lower during the active intervention phase compared with during the follow-up period. No major adverse event was reported apart from one study which recorded a non-fatal myocardial infarction.
Conclusion: This review demonstrated that VLCD in people with T2D was associated with significant weight loss, reduction in blood glucose profile and improvement in cardiovascular risk profile, high tolerability and good safety outcomes. Studies were heterogeneous and longer term outcomes data post VLCD is still required.