Whole Food for Families: A Pilot RCT of a Dietary Guidelines-Based Intervention to Prevent Type 2 Diabetes

This dietary program is based on empirical evidence showing that a diet pattern that favors minimally processed and whole foods (e.g., whole grains, fruits, vegetables, nuts) in contrast to diet patterns with greater consumption of highly refined and ultra-processed foods are attributed to greater reductions in HbA1c and fasting plasma glucose and a reduced risk for T2D. This evidence comes primarily from prospective cohort and clinical studies of 1) adult populations without diabetes (including type 2 and pre-diabetes) and 2) adult populations with active T2D. Studies of family dietary interventions for transgenerational T2D prevention are lacking.

Studies have focused primarily on structured diet patterns such as the Mediterranean style, Vegetarian or Vegan, Dietary Approaches to Stop Hypertension (DASH), carbohydrate-restricted, and low-fat. Evidence supports that the diet patterns most effective for T2D risk reduction focused on primarily whole food consumption (e.g., Mediterranean-style, Vegetarian, and DASH). Yet, less attention has been given to studying the effectiveness of the Dietary Guidelines for American's (DGA) diet pattern which forms the basis of nutrition advice in the U.S. and is the guiding nutrition framework used for federal nutrition policy. Moreover, a benefit of the recent DGA is its customizable approach to diet.

Recognizing the importance of a whole foods structured diet and the recent shift of the Dietary Guidelines for American's DGA diet pattern towards a customizable, family-centered, whole foods approach, studies that test the effectiveness of a DGA-structured diet for T2D risk reduction should be prioritized. Before conducting efficacy and effectiveness trails, pilot data is needed to determine the feasibility and acceptability of using this family- centered diet approach in a population at "high risk" for T2D. Applying a family- lens where a transgenerational approach can be used to prevent T2D is necessary.

Therefore, this program aims are to test the feasibility and acceptability of delivering a whole foods diet pattern using a family centered approach in a population at risk for T2D- adults with prediabetes and their "at-risk" biological offspring. This study will also test the preliminary effectiveness on the diet's effects on change in adult hemoglobin A1c at 12 months and will assess changes in diet quality during the intervention in adults and offspring.

Inclusion criteria

For this study, eligible adults will be those that:

• are 25 to 59 years of age at time of initial screen and identify as a parent to at least one child or adolescent 6-18 years;
• have a body mass index of between ≥23kg/m2 to <40kg/m2;
• have prediabetes (based on American Diabetes Association criteria of either fasting plasma glucose of ≥100 mg/dL, HgbA1c 5.7-6.4%, or 2-hour plasma glucose during 75-g oral glucose tolerance test [OGTT] 140 mg/dL to 199 mg/dL) with recent lab values reported within the prior 6-12 months and confirmed by an HbA1c A1cNow+ collected prior to enrollment (*see comment below);
• have no special dietary restrictions or food allergies that would prohibit consumption of a variety of foods/beverages;
• are English speaking;
• reside in Greater Nashville Tennessee and willing to come to Vanderbilt campus and Vanderbilt University Medical Center for required study visits;
• are without medical conditions that would limit participation in a diet-related study (e.g., tube feeding, dysphagia, severe food allergy causing anaphylaxis);
• are able to participate in a 12-week dietary program that requires home preparation/cooking for meals and snacks;

For this study, eligible offspring will be those that:

• Are 6-18 years at time of initial screen;
• Have an index parent with prediabetes that is actively enrolled in the program;
• have body mass index ≥5th percentile for age and gender on standardized CDC growth curves;
• have no special dietary restrictions or food allergies that would prohibit consumption of a variety of foods/beverages;
• have parental commitment to participate in a 12-week research study
• are English speaking;
• reside in the Greater Nashville Tennessee area and live at home with their index parent during the duration of 12- week study;
• are without medical conditions that would limit participation in a diet-related study (e.g., tube feeding, dysphagia, severe food allergy causing anaphylaxis);
• are able to participate in a 12-week dietary program that includes at least dinner and snacks provided during after-school hours;

Exclusion criteria

Adult exclusion criteria include:

• Adults who's HbA1c test is outside of the HbA1c range during screening* (see details related to screening results)
• adults outside the specified age range of <25 years or >59 years;
• adults whose body mass index is <23kg/m2 or those with a body mass index ≥40kg/m2 as that degree of morbid obesity represents a different phenotype where dietary behavioral intervention alone may not be sufficient to achieve weight loss);
• receiving care by a healthcare provider (i.e., MD, NP, PA) for a complicated diagnosis of prediabetes that requires routine glycemic monitoring or frequent healthcare visits for management/treatment;
• adults actively participating in any type of weight loss program (dietary or physical activity)
• adults with a prior history of type 2 diabetes;
• adults who are not English speaking or have limited English-language proficiency;
• adults with special dietary restrictions, food allergies, or medical conditions that prohibit participation in a diet-related study;
• adults with serious mental or neurologic illness that impairs the ability to consent/participate;
• women who are pregnant or nursing due to increased metabolic state requiring greater energy requirements;
• adults currently taking medications to treat diabetes or to promote weight loss;
• adults living outside Greater Nashville Tennessee or who are unwilling to travel to Vanderbilt for study visits;
• adults who do not otherwise meet the eligibility criteria listed in sections above as determined by pre-screen;

Offspring (child[ren] and adolescent[s]) exclusion criteria include:

• children/adolescents outside the specified age range of <6 years or >18 years;
• children/adolescents whose body mass index is <5th percentile for age and gender on standardized CDC growth curves;
• children/adolescents who do not have an eligible index parent participating in the study;
• children who do not have parental commitment to participate consistently for 12-weeks
• children/adolescents who are not English speaking or have limited English-language proficiency;
• children/adolescents with special dietary restrictions, food allergies, or medical conditions that prohibit participation in a diet-related study;
• children/adolescents who display dissenting behaviors during baseline data collection;
• children/adolescents actively participating in any type of weight loss program (medical or lifestyle);
• children/adolescents who do not otherwise meet the eligibility criteria listed in sections above as determined by pre-screen;