by Ashley Jordan Ferira, PhD, RDN
Almost 10% of the US population has diabetes, with another 34% in a precarious state of prediabetes.1 These diagnoses are not destiny. Research demonstrates that lifestyle interventions, particularly those incorporating nutrition therapy, produce clinically meaningful improvements in diabetes.2 Integrating this research foundation into the clinical setting is key. A study used an endocrinology private practice waiting room to deliver weekly group-based nutrition education classes for patients with type 2 diabetes (T2D), examining the effects of 2 eating plans: low-fat vegan vs. portion-controlled.3
This 20-week randomized clinical trial delivered weekly after-hours classes in the waiting room of a Washington, DC area clinical practice to adult patients (average age: 61) with well-controlled T2D (i.e., from medications) under the care of the same endocrinologist.3 Participants initially, privately met with a registered dietitian nutritionist (RDN) to develop an individualized eating plan, based on their randomization into either the vegan or portion-controlled eating plan.3 Then, weekly weigh-ins and weekly 1-hour group classes in the waiting room (chairs configured in a circle, accommodating ~15 patients) were conducted by an interdisciplinary team (RDN, nurse, physician, cooking instructor, or research staff) and covered information on diabetes, nutrition, meal planning, shopping, food preparation techniques, recipes, and interactive discussions on dietary challenges.3
Both groups were given a 100 mcg vitamin B12 supplement (taken every other day), and alcohol was limited to 1/day for women and 2/day for men. Characteristics specific to each dietary intervention included:3
- Vegan eating plan (“vegan”; n=19): low-fat (10%); low-to-moderate protein (10-15%); low-glycemic; no restrictions on energy or carbohydrate intake
- Portion-controlled eating plan (“PC”; n=21): portion size guidance; energy intake limits for weight loss (typically 500 kcal/day deficit); high-fiber food emphasis, carbohydrate distribution throughout day; saturated fat reduction; limited sodium intake
Food records, collected at baseline and 20-weeks, demonstrated that both groups reduced their calorie intake. When considered as % of energy:3
- Carbohydrate intake ↑ in both groups
- Fat intake ↓ in both groups (saturated fat and cholesterol ↓ more in vegan group)
- Protein intake ↓ in vegan group and ↑ in PC group
Both eating plans yielded significant improvements in multiple cardiometabolic outcomes:3
- ↓ Body weight (vegan: -6.3kg; PC: -4.4kg)
- ↓ Fasting glucose (vegan: -16.0 mg/dL; PC: 12.5 mg/dL)
- ↑ Glycemic control (both eating plans: HbA1c -0.40%)
- ↓ LDL cholesterol (vegan: -11.9 mg/dL; PC: -12.7 mg/dL)
At baseline, participants had average HbA1c <7.0% (reflects diabetes medications) and LDL cholesterol <100 mg/dL (reflects lipid-lowering medications); nonetheless, the dietary interventions and weekly classes integrated into the patient’s healthcare practitioner office resulted in significant, incremental improvements in relevant clinical measures.3 At the start of the study, participants were instructed to not alter their physical activity (PA) level; the patients deviated from the study design, with both groups increasing their PA during the study period, which could have theoretically also contributed to the clinical improvements seen in both groups.3
Although the study authors initially conjectured that the vegan eating plan would net superior clinical outcomes to the portion control approach,4 the study was statistically under-powered (they needed N=80; 40 in each group) to truly compare the 2 interventions and deduce differential effects.3 Future studies could address this limitation with a larger sample size.
Why is this Clinically Relevant?
- Lifestyle intervention research utilizing tailored, personalized nutrition therapy demonstrates clinically meaningful improvements in diabetes2
- Translating lifestyle medicine research into the clinical setting is critical to provide patients with efficacious care
- There are various eating patterns that produce meaningful reductions in clinical biomarkers, but the best pattern is the one that is sustainable over the long term
- Using a clinical practice’s waiting room provides an effective way to deliver group-based nutrition education that produces improvements in diabetes outcomes3 and is likely a replicable delivery format for other chronic diseases with underlying nutrition-related etiologies
- CDC. National Diabetes Statistics Report. https://www.cdc.gov/diabetes/data/statistics/statistics-report.html. Accessed June 25, 2018.
- American Diabetes Association. Standards of medical care in diabetes-2017: Lifestyle management. Diab Care. 2017;40(Suppl 1):S33-S43.
- Barnard ND, Levin SM, Gloede L, Flores R. Turning the waiting room into a classroom: weekly classes using a vegan or a portion-controlled eating plan improve diabetes control in a randomized translational study. J Acad Nutr Diet. 2018;118(6):1072-1079.
- Barnard ND, Katcher HI, Jenkins DJA, Cohen J, Turner-McGrievy G. Vegetarian and vegan diets in type 2 diabetes management. Nutr Rev. 2009;67(5):255-263.