Patients with type 2 diabetes who follow a low-carbohydrate diet (LCD) for at least 6 months appear to have significantly higher remission rates than those following other diets, although the benefits diminish by 12 months, suggests a new analysis of trial data from over 1,300 individuals.
“Based on other evidence, it is likely the degree of weight loss would have been a contributing factor, combined with the lower intake of dietary carbohydrates,” study coauthor Grant D. Brinkworth, PhD, Commonwealth Scientific and Industrial Research Organisation, Sydney, , said in an interview.
He acknowledged, however, that “diets in general can be difficult to sustain over the long term. ... We need to provide patients with easy-to-use support tools and convenient solutions to help them adhere to a low-carb diet long term to gain these greater health improvements.
“In addition, more long-term, well-controlled, randomized trials are needed to determine the effects of low-carb diets on sustained weight loss, diabetes remission, and health outcomes,” Dr. Brinkworth added.
The research was published on Janu. 13 in the BMJ by a consortium of international scientists, led by Joshua Z. Goldenberg, PhD, department of nutrition, Texas A&M University, College Station.
Confusion as to best diet for those with diabetes
Type 2 diabetes is a “significant and worsening” worldwide health problem, wrote Dr. Goldenberg and coauthors, in spite of “many pharmaceutical developments and a global emphasis on glycemic control.”
Although structured diets are “recognized as an essential component of treating diabetes, confusion remains about which diet to choose,” with multiple systemic reviews and meta-analyses of carbohydrate-restricted diets “reporting mixed results,” they noted.
They therefore undertook a systematic review of randomized, controlled trials on the efficacy and safety of LCDs and very-low-carbohydrate diets (VLCDs) using the CENTRAL, Medline, CINAHL, and CAB databases, as well as other literature sources.
Researchers defined LCDs as less than 130 g/day of carbohydrates or less than 26% of calories from carbohydrates as part of a 2,000 kcal/day diet and VLCDs as less than 50 g/day or less than 10% of daily calories. They focused on interventions that lasted at least 12 weeks in adults with type 2 diabetes.
Overall, 23 trials involving 1,357 participants met the inclusion criteria; 52% used VLCDs and the control comparator was a low-fat diet in 78% of the studies. The mean age range of patients was 47-67 years, and treatment duration spanned from 3 months to 2 years.
LCDs were associated with a higher rate of diabetes remission when defined as a hemoglobin A1c level of less than 6.5%, compared with control diets at 6 months, at 57% versus 31% – an increase in remission of 32% associated with LCDs (P < .001 for overall effect).
But when defined more tightly as an A1c level of less than 6.5% in the absence of diabetes medications, remission with LCDs was reduced to a nonsignificant 5% versus control diets at 6 months.
At 12 months, data on remission were sparse, ranging from a small effect to a trivial increased risk of diabetes.
Subgroup analysis demonstrated that patients on an LCD achieved greater weight loss at 6 months than those on a control diet, at a mean reduction of 3.46 kg (approximately 7.6 lb). However, the researchers noted that, at 12 months, any weight-loss benefit was “trivial and nonsignificant.”
A similar pattern was seen for reductions in A1c and fasting glucose levels with LCDs: Notable reductions at 6 months largely disappeared by 12 months.
LCDs were also associated with “greater reductions in diabetes medication and clinically important benefits” in triglycerides and insulin resistance at 6 and 12 months, the team wrote.