Leigh Forsyth was born on 17 December 1915, the son of Dr Robert Leslie Forsyth, who was prominent in the medical world of Melbourne as a general practitioner and as an inpatient physician at the Children's Hospital. Leigh was educated at Scotch College, Melbourne. He was widely read and played a leading part in the Dramatic Society and the Scout Troop. He matriculated with honours in English and biology, and then proceeded to the medical course at the University of Melbourne in 1933. He gained a blue in Rugby and at graduation he was the youngest in his year, and was awarded the Fulton Scholarship for obstetrics and gynaecology.

He was a junior resident at the Royal Melbourne Hospital when he met Patricia Bartram, a trainee nurse at the Hospital whom he was later to marry. Patricia's father, Dr Roy Bartram, succeeded to the late Sir Harry Wunderly's practice at Mount Barker, SA before moving to Melbourne, where the Bartram and Forsyth families became closely associated.

In 1940 he enlisted in the 2nd AIF and was posted to the Middle East where he served in Palestine and Syria and was with the 2/8 Field Ambulance at El Alamein. In 1944 he was promoted to major as a specialist physician and he served in various hospitals in Australia, New Guinea and Borneo. Before discharge from the Army in 1946, he became a Member of the College and then came under the influence of Dr `Jock' Williams, an old family friend.

Jock was appointed to the diabetic clinic at the Royal Melbourne Hospital in 1928, probably the first specialist in this field in Melbourne. In 1947, Leigh decided that diabetes was to be his career and joined Jock, as an assistant in his clinic, in 1947. This was not to be, as in 1949 Leigh developed a tuberculous pleural effusion and spent the next twelve months or so in the Repatriation General Hospital, Heidelberg. After this his convalescence was prolonged by a relapse, precipitated by a motor car accident. Leigh became interested in diseases of the chest and joined the Repatriation Department as a specialist in this field. In 1954 he received a World Health Organisation scholarship, travelled to England to study the treatment and public health aspects of tuberculosis, and then acted as an adviser to the Government of Ceylon in the formation of their Tuberculosis Service. In the late 1950s he succeeded Dr Alan Penington as consultant in diseases of the chest at the Central Office of the Repatriation Department, returning in 1960 to the Victorian branch as principal medical officer.

He had a special interest in boating, fishing and Scottish dancing and played tennis with enthusiasm. His was a complex character; he had a very strong personality, was a very clear thinker and was a good administrator. In his later life his health gradually deteriorated, he spent much of his remaining years in hospital, and died on 18 August 1970. He was survived by a son, a cardiothoracic surgeon, and two daughters.