**5. Conclusions**

Late adolescence to early adulthood is a period of significant change and represents an important window in which to establish lifelong habits [29]. To our knowledge, this study is one of few to evaluate the impact of dietary changes on glucose regulation in people between the ages of 18 and 30. We found that adherence to the DASH diet and USDA Dietary Guidelines is associated with reduced risk for prediabetes and better glucose tolerance. Improvement in DASH or HEI scores over the follow-up period was also associated with lower risk for prediabetes or type 2 diabetes, with the strongest effects observed for the DASH diet. These findings indicate that the DASH dietary pattern may be a promising target for diabetes prevention efforts in young adults.

**Supplementary Materials:** The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/nu14183734/s1, Figure S1: Flowchart for study recruitment; Table S1: Results (effects and 95% CIs) for sensitivity analyses at the baseline visit; Table S2: Results (effects and 95% CIs) for sensitivity analyses at the follow-up visit; Table S3: Results (effects and 95% CIs) for sensitivity analyses for the effects of change in diet score between visits; Table S4: Estimated effect size and 95% CI for the relationship between body composition and risk for prediabetes/type 2 diabetes).

**Author Contributions:** Conceptualization, E.C., J.G. and L.C.; data curation, E.C., J.G., W.B.P. and S.R.; formal analysis, E.C., W.B.P. and Y.L.; funding acquisition, L.C.; investigation, E.C., J.G. and S.R.; methodology, E.C., J.G., W.B.P., Z.C., T.L.A., D.V.C. and L.C.; resources, F.G., Z.C., T.L.A. and L.C.; supervision, J.G., B.B., F.G., M.I.G., Z.C., T.L.A., D.V.C. and L.C.; visualization, E.C. and J.G.; writing original draft, E.C.; writing—review and editing, J.G., W.B.P., S.R., Y.L., B.B., F.G., M.I.G., Z.C., T.L.A., D.V.C. and L.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** The results reported here in correspond to specific aims of grand R01ES029944 from the National Institute of Environmental Health Science (NIEHS). Funding for the MetaAir study came from the Southern California Children's Environmental Health Center grants funded by NIEHS (5P01ES022845-03, P30ES007048, 5P01ES011627), the United States Environmental Protection Agency (RD83544101), and the Hastings Foundation. Additional funding from NIEHS supported E.C. and J.G. (T32ES013678), Z.C. (R00ES027870, R00ES027853), T.L.A. (R00ES027853), D.V.C. (R01ES030691, R21ES029681, R01ES030364, R01ES016813), and L.C. (R01ES030691, R21ES029681, R01ES030364, R21ES028903). Other sources of funding included the National Institute for Diabetes and Digestive and Kidney Diseases (F31DK134198, W.B.P.; P30DK048522, D.V.C.), the National Cancer Institute (P01CA196569 and R01CA140561, D.V.C.), and the USC Center for Translational Research on Environmental Health (S.R.).

**Institutional Review Board Statement:** The study was conducted in accordance with the Declaration of Helsinki and approved by the Institutional Review Board of the University of Southern California (HS-19-00338; 3 June 2019).

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available to protect participants' identifiable information.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

## **References**

