What is the effect of a very low calorie diet on glycaemic control in people with type 2 diabetes mellitus?

Problem

There are 3.6M people in the UK living with Type 2 Diabetes Mellitus (T2DM), a number expected to reach 5M by 2025. The majority are managed in general practice.Good glycaemic control (HbA1c<58mmol/mol) is essential to minimise risk of complications but only achieved by two-thirds of patients. 80% people with T2DM are overweight or obese, the main risk factor for disease progression.Diabetes and its consequences account for 10% of the entire NHS budget, making cost-effective ways to reduce its impact on patients, the NHS and wider society a priority.Very Low Calorie Diets (VLCDs) are nutritionally complete, energy restricted, total meal replacement diets of <800kcal/day. VLCDs can result in rapid weight loss and normalisation of glycaemic levels within seven days.

Approach

A systematic review and meta-analysis to address the question: What is the effect of a VLCD on glycaemic control in people with T2DM? (PROSPERO: CRD42016050197)Key databases (e.g. Embase, Medline/OVID, CINAHL) were searched from inception to December 2016 using the terms: Very Low Calorie Diet OR Very Low Energy Diet OR VLCD OR VLED OR Total Diet Replacement OR Total Meal Replacement OR Meal Replacement AND Type 2 Diabetes Mellitus OR T2DM. Reference lists were hand-searched.Inclusion criteria: patients aged >18yrs with T2DM, using a VLCD intervention, reporting HbA1c or fasting blood glucose as an outcome, any study design.A narrative synthesis was undertaken and a meta-analysis of HbA1c & fasting blood glucose is underway.

Findings

Database searches identified 3259 papers with 29 eligible for inclusion. There were six RCTs, but most were observational studies. 23 studies were community or primary care based.VLCD intervention duration raged from 2-33 weeks. Four interventions also included an exercise component and nine included behaviour change counselling or support.All studies reported significant improvements in glycaemic control and reductions in body weight. Blood pressure and cholesterol were also significantly lowered in studies which reported them. Weight loss was more rapid than using a standard low calorie diet. The effect of a VLCD on weight loss and glycaemic control was comparable to bariatric surgery.Participant adherence and retention was good, but reporting of adverse effects was limited as was information about long-term efficacy.Findings of the meta-analysis will be presented.

Consequences

These findings confirmed that VLCDs can lead to significant weight loss and improved glycaemic control in people with T2DM. VLCDs appear to be as acceptable as other treatments in obese people with T2DM suggesting that they may provide an alternative, non-invasive method of managing T2DM in the primary care setting.Evidence of long-term efficacy and cost-effectiveness, however, is lacking. Primary care based randomised controlled trials with long-term follow-up are needed to address these questions.