Challenges in designing and delivering diets and assessing adherence: A randomized controlled trial evaluating the 2010 Dietary Guidelines for Americans

Authors: KRISHNAN, SRIDEVI - University Of California, Davis; LEE, FANNY - University Of California, Davis; BURNETT, DUSTIN - University Of California, Davis; KAN, ANNIE - University Of California, Davis; BONNEL, ELLEN - University Of California, Davis; Allen, Lindsay - A; ADAMS, SEAN - University Arkansas For Medical Sciences (UAMS); Keim, Nancy

Submitted to: Current Developments in Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2020
Publication Date: 2/13/2020
Citation: Krishnan, S., Lee, F., Burnett, D.J., Kan, A., Bonnel, E.L., Allen, L.H., Adams, S.H., Keim, N.L. 2020. Challenges in designing and delivering diets and assessing adherence: A randomized controlled trial evaluating the 2010 Dietary Guidelines for Americans. Current Developments in Nutrition. 4(3). https://doi.org/10.1093/cdn/nzaa022.
DOI: https://doi.org/10.1093/cdn/nzaa022

Interpretive Summary: In nutrition research, a controlled feeding trial provides the strongest scientific evidence about the effects of a diet, food, or food component, yet there are very few guidelines or standardized methods for designing menus for this type of study. This report provides a description of how menus for two diet patterns, one based on the Dietary Guidelines for Americans and the other a typical American diet based on the NHANES surveys, were designed and delivered to participants. So the volunteers were not able to distinguish between diets and know their intervention assignment, the two diet patterns were made to look very similar to each other by altering recipes, adjusting proportions of ingredients. In addition, tools for monitoring adherence to the provided diets are described, along with the results for the participants assigned to the Dietary Guidelines group and typical American diet group. No differences were found in adherence to the provided diet between the two diet groups and, on average, more than 95% of the provided foods were eaten by participants. Finally, in an exit survey the majority of participants agreed that the diet they received was satisfying, but other questions related to dimensions of taste and familiarity yielded a wide range of responses. The research procedures and tools presented in this manuscript will be useful to investigators planning controlled feeding trials for participants who are free-living.

Technical Abstract: Background: Controlled feeding trials are challenging to design and administer in a free-living setting. There is a need to share methods and best practices for diet design, delivery, and standard adherence metrics. Objective: This report describes menu planning, implementing and monitoring of controlled diets for an 8-wk free-living trial comparing a diet pattern based on the 2010 Dietary Guidelines for Americans (DGA) and a more typical American diet (TAD) pattern based on NHANES survey (2009-2010). The objectives were to: 1) provide meals that were acceptable, portable, and simple to assemble at home, 2) blind the intervention diets to the greatest extent possible, and 3) develop tools for monitoring adherence. Methods: Menus were blinded by placing similar dishes on the two intervention diets, but changing recipes. Adherence was monitored using daily food checklists; real-time dashboard of scores from daily checklist; weigh-backs of containers returned; and 24-h urinary nitrogen recoveries. Proximate analyses of diet composites were used to compare the macronutrient composition of the composite and planned menu. Results: Meeting nutrient intake recommendations while scaling menus for individual energy intake levels and food portions was most challenging for vitamins D and E, sodium-potassium ratio, dietary fiber, and fatty acid composition. Dietary adherence for provided foods was >95%, with no differences between groups. Urinary nitrogen recoveries were ~80% relative to nitrogen intake and not different between groups. Composite proximate analysis matched the plan for dietary fat, protein, and carbohydrates. Dietary fiber was ~2.5 g higher in the TAD composite compared to planned, but ~7.4 g lower than DGA composite. Conclusions: Both DGA and TAD diets were acceptable to most participants. This conclusion was supported by self-reported consumption, quantitative weigh-backs of provided food, and urinary nitrogen recovery. Dietary adherence measures in controlled feeding trials would benefit from standard protocols to promote uniformity across studies.