Efficacy of Low- and Very-Low-Energy Diets in people with Type 2 Diabetes Mellitus: A systematic review and meta-analysis of interventional studies.

AIMS: To systematically review and quantify the weight loss achieved by Low- and Very-Low-Energy Diets in people with type 2 diabetes mellitus. MATERIALS AND METHODS: Studies reporting the effects of diet-only interventions up to 1600kcal/day in people with type 2 diabetes mellitus were searched in MEDLINE, EMBASE, CINAHL until July 2018. Changes in the primary (body weight and body mass index) and secondary (HbA1c, blood lipids) outcomes according to energy restriction and duration of diet were modelled using restricted cubic splines. RESULTS: Forty-four studies (3817 participants) were included. The overall quality of the evidence was moderate and limited to short-term interventions up to four months. Baseline mean weight and body mass index were 92.1kg and 36.6kg/m2 . Very-Low-Energy Diets of 400kcal/day led to 5.4% weight loss at two weeks, increasing to 17.9% at three months. More modest reductions of 7.3% were observed on Low-Energy Diets of 1200kcal/day and 2.0% on 1600kcal/day after three months. No clear patterns emerged for secondary outcomes. Publication bias was significant for primary outcomes. CONCLUSIONS: High-quality studies are required to support evidence-based Low- and Very-Low Energy prescription in people with type 2 diabetes. Available evidence would suggest variable reduction of body weight, ranging from 2% to 18%, after three months of Low- and Very-Low-Energy Diets.