November 18, 2021
3 min read
Churuangsuk reports receiving support with a PhD scholarship from the Prince of Songkla University, Thailand. Please see the study for all other authors’ relevant financial disclosures.
Weight-loss programs that include very low-energy diets and formula meal replacements are the most effective for weight loss in type 2 diabetes, according to a systematic review published in Diabetologia.
In a review of 19 meta-analyses, researchers also found that programs with a total diet replacement induction phase were the most effective dietary approach for type 2 diabetes remission, with up to 61% of participants achieving normoglycemia at 1 year.
“All people with type 2 diabetes should be offered a well-designed, professionally supported, structured diet program that is evidence-based, with the aim of achieving and sustaining at least 10 kg weight loss,” Mike Lean MA, MB BChir, MD, FRCP, FRSE, professor of human nutrition and consultant physician at the University of Glasgow and an adjunct professor at the University of Otago, told Healio. “That is possible with many diets, and no specific diet type has proved better than others. The best results are with a two-phased program, using a low-calorie (600-900 kcal/day) induction phase with a nutritionally balanced formula diet, unless individuals prefer a food-based approach. This can be delivered successfully in primary care, with attention to medication dose adjustments for glucose-lowering and antihypertensive drugs.”
Churuangsuk and colleagues identified 21 systematic reviews with 19 meta-analyses of randomized controlled trials of weight-loss diets conducted through May 2021. Researchers synthesized weight-loss findings, stratified by diet types, and assessed meta-analyses quality and the certainty of pooled results of each meta-analysis using Grading of Recommendations, Assessment, Development and Evaluations (GRADE).
Of the 19 meta-analyses, 18 reported direct comparisons of specific diets. Most meta-analyses were of critically low (n = 7) to low quality (n = 5); only seven meta-analyses were assessed as high quality.
“Planned analysis of associations between changes in energy intake and weight changes from baseline, to differentiate effects of energy restriction and dietary regimen, proved impossible from the published information,” the researchers wrote.
Researchers found the greatest weight loss was reported with very low-energy diets of 400 kcal to 500 kcal per day for 8 to 12 weeks, achieving 6.6 kg greater weight loss than low-energy diets of 1,000 kcal to 1,500 kcal per day (95% CI, –9.5 to –3.7). One high-quality meta-analysis of nine randomized controlled trials reported that replacing one to three main meals daily (13% to 47% total energy) achieved 2.4 kg greater weight loss over 12 to 52 weeks (95% CI –3.3 to –1.4) compared with low-energy diets, according to researchers.
Low-carbohydrate diets were no better for weight loss than higher-carbohydrate/low-fat diets, with the researchers noting the evidence was high quality. High-protein, Mediterranean, high-monounsaturated fatty acid, vegetarian and low-glycemic index diets all achieved minimal or no difference from control diets, though researchers cautioned the quality of those studies was low to critically low quality; GRADE ranged from very low to moderate.
For two randomized controlled trials assessing type 2 diabetes remission as the primary outcome, researchers found that, compared with usual care control arms, programs that included an induction phase of formula total diet replacement were associated with a median of 54% remission at 12 months from baseline. Among trials reporting post hoc analyses for remission, using two meal replacements per day for up to 20 weeks and one per day thereafter reported 11% remission at 1 year compared with 2% with standard care. A single randomized controlled trial assessing a Mediterranean diet over 12 months reported a diabetes remission prevalence of 15% compared with 4% in the control low-fat diet arm.
For ketogenic/very low-carbohydrate and very low-energy food-based diets, researchers wrote, the evidence for remission had “serious and critical risk of bias,” with very low GRADE certainty.
“The analyses contradict some popular claims about specific diets: In particular, ‘low-carb’ diets hold no overall advantage for weight loss when compared with higher-carbohydrate diets,” Chaitong Churuangsuk, MD, a doctoral student in the department of human nutrition at the University of Glasgow, and colleagues wrote.. “However, we cannot conclude that any individual with type 2 diabetes, in any context, will do equally well with any diet advice, or that a skilled practitioner may not have greater success advising one diet type.”
The researchers noted that most of the evidence is restricted to 1 year or less and more research is needed to assess longer-term impacts on weight, glycemic control, clinical outcomes and diabetes complications.
“We are actually quite good at helping people lose enough weight. We need research to show us how to help more people succeed,” Lean told Healio. “The big need is to find better ways to help people avoid returning to the eating patterns which caused them to gain weight and develop type 2 diabetes.”
For more information:
Mike Lean MA, MB BChir, MD, FRCP, FRSE, can be reached at [email protected].