**5. Conclusions**

The present study is the first to assess the effects of pre-sleep LGI versus HGI CHO supplementation on next-morning exercise metabolism, GID, and endurance performance in male and female endurance athletes. The data indicate that pre-sleep supplementation with LGI, HGI, or PLA did not differ in GID response during exercise. There were no differences between supplements for resting REE or RER, BG, or TT performance. In a secondary analysis, there was an interaction of supplement and sex for FAT and CHO utilization at baseline with females utilizing more CHO with the pre-sleep LGI and HGI, which should be explored further. In this study, consuming a CHO supplement pre-sleep, and not within a couple of hours of exercise, might reduce GID, allowing for adequate digestion and absorption. Future studies should investigate the effect of pre-sleep CHO supplementation on the endurance performance of the following morning.

**Author Contributions:** Conceptualization, M.J.O., M.D.D., and S.J.I.; methodology, M.D.D., M.J.O., S.J.I.; formal analysis, M.D.D., E.D.B., K.R.F., R.A.B., M.M.C., N.R.M., M.J.O., S.J.I.; investigation, M.D.D., E.D.B., K.R.F., R.A.B., M.M.C., N.R.M., M.J.O., S.J.I.; resources, M.J.O., S.J.I.; data curation, M.D.D., E.D.B., K.R.F., R.A.B., M.M.C., N.R.M., M.J.O., S.J.I.; writing—original draft preparation, M.D.D., E.D.B., K.R.F., R.A.B., S.J.I.; writing—review and editing, M.D.D., E.D.B., K.R.F., R.A.B., M.M.C., N.R.M., M.J.O., S.J.I.; visualization, M.D.D., E.D.B., K.R.F., R.A.B., M.M.C., N.R.M.; supervision, S.J.I., M.J.O.; project administration, S.J.I., M.J.O. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** Foremost, the authors deeply appreciate and thank all study participants. We thank UCAN for the donation of the UCAN superstarch to MJO for this study and the Skidmore Student Opportunity Fund for providing modest financial assistance to help with the completion of this study.

**Conflicts of Interest:** The authors declare no conflict of interest.
