[1][9][10][11] Parker's vegetarian diet consisted of cereals, fruit, milk, nuts, vegetables and a liberal amount of eggs.

[12][13] In April, 1903 Parker authored an article on physical culture in the San Francisco Call, advocating a vegetarian diet for health reasons.

[13] In 1905, Parker was described as "one of the most gentlemanly fighters in the prize ring today".

[3] After his boxing career ended Parker was institutionalized in an asylum at Norfolk, Nebraska as he suffered from hallucinations.

[17][18] Parker would repeatedly punch the wall in his padded cell so was given boxing gloves to protect his hands.