1. For patients newly diagnosed with type 2 diabetes, weight loss achieved through early dietary intervention was strongly associated with lower HbA1c between 0 and 6 months
2. Increases in “carb/fat balance” diet were associated with improvements in HbA1c at 6 months independent of weight loss
Level of evidence assessment: 1 (Excellent)
Summary of the study: Diet is a mainstay of treatment for patients diagnosed with type 2 diabetes mellitus (T2DM). Nutrition guidelines for blood sugar management focus on individualized recommendations rather than a “one size fits all” approach. Improved HbA1c concentrations are consistently associated with weight loss achieved through dietary changes. However, it is unclear whether various diets can benefit glycemic control beyond their effect on body weight. This randomized controlled trial, called the Early-ACTivity-In-Diabetes trial, aimed to assess whether changes in eating habits impair glycemic control independent of effects on body weight in patients with newly diagnosed T2D. A total of 593 adults diagnosed in the previous 5-8 months with T2D were recruited from December 2005 to September 2008 in South West England. Participants were randomized to usual care, dietary intervention, or diet and physical activity intervention. During the first 6 months of the study, the hypoglycemic drugs were not changed. The endpoints of the trial were HbA1c and blood pressure at 6 months (primary) and 12 months (secondary) after the intervention. Over 6 months, reductions were observed in mean body weight (−2.3 (95% CI: −2.7, −1.8) kg), body mass index (−0.8 ( −0.9, −0.6) kg/m2), energy intake (−788 (−953, −624) kJ/day) and HbA1c (−1.6 (−2.6, -0.6) mmol/mol). Weight loss was strongly associated with lower HbA1c between 0 and 6 months (b = − 0.70 [95% CI − 0.95, − 0.45] mmol/mol/kg lost). Increases in “carbohydrate/fat balance” diet (characterized by increased consumption of fresh fruit and low-fat milk and lower consumption of red meat and butter/animal fat) were associated with improvements in HbA1c at 6 months, regardless of weight loss (b= − 1.54 [− 2.96, − 0.13] mmol/mol/SD). Promoting weight loss should remain the primary nutritional strategy to improve glycemic control in early T2DM. However, improving dietary habits that lead to increased carbohydrate/fat balance may provide additional improvements in glycemic control.
Click here to read the study in BMC Medicine
Relevant reading: Diets and type 2 diabetes: systematic literature review and meta-analysis of prospective studies
In depth [Randomized Controlled Trial]: The Early ACTID trial, a 12-month multicentre, parallel-group, randomized controlled trial, recruited 593 adult participants from the South West of England and randomly assigned them to one of three groups, namely care usual, dietary intervention or diet and physical activity intervention. Usual care consisted of standard dietary and physical counseling at 0 and 12 months, with an interim review by study physicians and nurses at 6 months, where no further counseling was given. The dietary intervention aimed to achieve and maintain 5-10% weight loss through a non-prescriptive dietary intervention based on a number of UK guidelines. Specifically, participants were encouraged to eat starchy foods and choose high fiber/whole grain options, reduce added sugars, increase fatty fish, and reduce fatty and processed meat intakes. Dietitians met with participants at randomization and every 3-4 months, with study nurses reinforcing counseling every 6 weeks. The diet and physical activity intervention consisted of the same dietary intervention as the diet alone group, plus walking ≥ 30 min ≥ 5 days per week. Diet was self-reported using 4-day food diaries. Initially, a “carbohydrate/fat balance” diet and an “obesogenic” dietary pattern were derived using reduced-rank regression, based on hypothetical nutrient-mediated mechanisms linking food intake to blood sugar directly or via obesity. Relationship between change at 0 and 6 months in dietary habit scores and adjusted baseline HbA1c at 6 months (not= 242; primary endpoint) were assessed using multivariate linear regression. The models were repeated for periods of 6 to 12 months and 0 to 12 months (not= 194 and not= 214 respectively; secondary results). Initially, 593 participants were included. In addition, two diets, a “carbohydrate/fat balance” diet (characterized by a higher percentage of energy from starches and sugars and a lower percentage of energy from fat) and an “obesogenic” dietary pattern (characterized by higher energy density in fat, low fiber diet), were identified. Mean weight, body mass index (BMI), total energy intake (TEI), and HbA1c all decreased over 0 to 6 months (mean change: −2.3 (95% CI: −2 .7, − 1.8) kg; − 0.8 (− 0.9 , − 0.6) kg/m2; -788 (-953, -624) kJ; – 1.6 (- 2.6, – 0.6) mmol/mol [− 0.15 (− 0.24, − 0.06) %]). There was strong evidence that increases in ‘carb/fat balance’ eating habits scores were associated with reductions in HbA1c between 0 and 6 months (Model 2: b= − 2.21 [− 3.65, − 0.78] mmol/mol/SD; p= 0.003). There was no evidence of an association between changes in ‘obesogenic’ diet scores and changes in HbA1c. It was concluded that, in newly diagnosed patients with T2D, promotion of weight loss should remain the main nutritional strategy to improve glycemic control. Increasing the carbohydrate/fat balance can further improve HbA1c.
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