Dr. Baker was a principal investigator and member of the steering committee for the 10-year study, known as the Diabetes Control and Complications Trial.
In his 35-year career, he also pioneered research showing a connection between family dynamics and diabetes control and cowrote, with Dr. Salvatore Minuchin, Psychosomatic Families: Anorexia Nervosa in Context (published by Harvard University Press in 1978). The book helped bring family therapy into the treatment of poorly controlled diabetes in children.
While Dr. Baker had an impressive body of research, which included being an international leader in the field of neonatal hypoglycemia and hyperinsulinism, he also was well regarded as a clinician and teacher. In 1994, he received an award as outstanding clinician in diabetes from the American Diabetes Association.
"His patients loved him. They absolutely adored him because of his personality," said Dr. Seth Braunstein, chief of the diabetes program at the Hospital of the University of Pennsylvania. "He cared about them. He took care of them. He loved them back. Each of his patients was like his children."
Dr. Baker was also a generous teacher who "brought us all along and encouraged us," said Dr. Paul Thornton, an endocrinologist and assistant professor of pediatrics at the University of Pennsylvania School of Medicine.
"He didn't keep his brilliance for his own advancement. He spread it all around and brought people with him. He had a very incisive mind. He could see a problem and know what to do."
Dr. Baker's manner was gentle, patient, kind and empathetic, with a dose of humor, according to colleagues and family.
His life, they added, revolved around his family, his work and tennis.
His son, H.P. Baker, of Philadelphia, said he found it remarkable that his father had "no ego."
"People on the tennis court knew him as 'Les the tennis bum,' " his son said. "No one knew that there was a world-class endocrinologist next to him."
Besides his son, Dr. Baker is survived by his wife, Liesel Baker; a daughter, Deborah White of Cranford, N.J.; and two grandchildren.
Services will be held at 1 p.m. today at Society Hill Synagogue, 418 Spruce St., Philadelphia. Interment will be in Har Jehuda Cemetery, 8400 Lansdowne Ave., Upper Darby.
Contributions may be made to the Diabetes Research Center at the Children's Hospital of Philadelphia, One Children's Center, 34th and Civic Center Boulevard, Philadelphia 19104.
Marian Uhlman's e-mail address is firstname.lastname@example.org