An after-hours group-based nutrition class given alongside medication significantly improved weight, glycemic control, and cholesterol levels among patients with type 2 diabetes, regardless of which diet plan they were assigned to, results of a US randomized controlled study suggest.
The study of more than 40 patients with type 2 diabetes indicated that, after 20 weeks of following a vegan or portion-controlled diet supported by weekly group nutrition classes, patients had significant reductions in HbA1c and low-density lipoprotein cholesterol (LDL-C), as well as body mass index (BMI).
The research was published online in the Journal of the Academy of Nutrition and Dietetics.
In a press release by the Physicians Committee for Responsible Medicine, lead author Neal D Barnard, MD, George Washington University School of Medicine, Washington, DC, described the dietary interventions as “simple and very effective.”
“Doctors can turn their waiting rooms into classrooms….Patients learn about healthy food changes and can share tips, swap recipe ideas, and work through challenges together.”
He added, “Nutrition is one of the most powerful tools we have in the fight against diabetes. This study shows that even clinicians who are pressed for time can harness that power by offering group instruction to their patients.”
Translating Research Findings Into the Clinic
Dietary interventions are associated with improvements in diabetes management, and low-fat vegan eating plans can be particularly beneficial in terms of weight, glycemic control, and lipids.
However, translating research findings into the clinical setting has been challenging, as office-based practices may not have dietetic professionals or the physical space for classes, and changes in eating pattern can be confounded by medication alterations.
For the current study, the team examined whether weekly nutrition classes in a typical endocrinology practice would improve glycemic control, body weight, and plasma lipid concentrations, as well as blood pressure and indices of renal function.
They randomized patients with well-controlled type 2 diabetes who had a BMI of ≤ 45 kg/m2 and didn’t consume more than two alcoholic drinks daily, to a low-fat vegan or portion-controlled eating plan.
The low-fat vegan plan favored low-glycemic index foods and excluded animal products and oils, while the portion-controlled plan included energy intake limits for weight loss, typically set at a deficit of 500 calories/day.
Participants attended 20 weekly after-hours classes in the office waiting room, which included information on diabetes nutrition, meal planning, shopping, food preparation techniques, recipes, and discussion of everyday dietary challenges. Food records were completed at baseline and 20 weeks.
Of the 45 participants, 21 patients were assigned to the vegan group and 24 patients were assigned to the portion-controlled group. Their average age was 61 years, and there were no significant differences in baseline characteristics between the two groups. Four participants (two in each group) did not complete the study.
Researchers found that both groups reduced their energy intake while increasing carbohydrate intake as a proportion of energy, from 49% to 71% in the vegan group and from 43% to 50% in the portion-controlled group (P = .0013).
Although fat intake as a percentage of energy decreased in both groups, there was a divergence in the percentage of energy from protein, which decreased in the vegan group, from 18% to 14%, but increased in the portion-controlled group, from 19% to 21% (P = .0004).
Body weight decreased by 6.3 kg in the vegan group and 4.4 kg in the portion-controlled group (P < .001 for both), while BMI fell by 2.3 and 1.5 kg/m2, respectively (P < .001 for both).
HbA1c decreased by a median of 0.4 percentage points in the vegan (P < .05) and portion-controlled groups (P ≤ .01). Median fasting glucose fell by a nonsignificant 16.0 mg/dL in the vegan group and 12.5 mg/dL in the portion-controlled group.
LDL-C levels were reduced by 11.9 mg/dL in the vegan group and 12.7 mg/dL in the portion-controlled group (P ≤ .01 for both). There was a nonsignificant increase in triglycerides in the vegan group, but a significant decrease of 24.9 mg/dL in the portion-controlled group (P ≤ .01).
In terms of clinical changes, there were no significant differences between the two dietary interventions. There were no meaningful changes in urinary albumin or blood pressure levels.
The researchers note that the study had numerous limitations, such as recruitment falling “short of the numbers called for by the power analysis, because of having exhausted the patient population of the practice.” Also, with the support being greater than that typically provided in the clinical setting, there were changes in medication that “complicated the interpretation of study findings” and produced uncertainty over the level of adherence.
And “the study took place in the late winter and spring, a time when physical activity would naturally increase.”
They continue, “Despite these limitations, this study has demonstrated that a simple program of instruction and support leads to significant improvements in diabetes management.”
“In future studies, testing the effects of a program of this type in a larger participant group with less well-controlled diabetes, lipid values, or blood pressure would be helpful,” they conclude.
The study was supported by the Physicians Committee for Responsible Medicine. Barnard writes books and articles and gives lectures related to nutrition and health, and has received royalties and honoraria from these sources. Barnard, Susan M Levin, and Rosendo Flores are affiliated with the Physicians Committee for Responsible Medicine.
J Acad Nutr Diet. Published online February 1, 2018. Full text