Here is his research. You have to pay to access the full study, but it exists. But here is the abstract.

https://www.sciencedirect.com/science/article/pii/S0074774208602913?via%3Dihub

Furthermore, here are other studies that report similar results and also cite Barker's research. Research cannot begin on humans, it is unethical. It almost always starts with animals.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6597727/ Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI USA

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5048497/ Department of Psychiatry and Behavioral Sciences Johns Hopkins University School of Medicine Baltimore, MD