In 1898, Fisher was diagnosed with tuberculosis, the same disease that had killed his father. He spent three years in sanatoria, finally making a full recovery. That experience sparked in him a vocation as a health campaigner. He was one of the founders of the Life Extension Institute, under whose auspices he co-authored the bestselling book "How to Live: Rules for Healthful Living Based on Modern Science", published in 1915. He advocated regular exercise and the avoidance of red meat, tobacco, and alcohol. In 1924, Fisher wrote an anti-smoking article for the "Reader's Digest", which argued that "tobacco lowers the whole tone of the body and decreases its vital power and resistance ... acts like a narcotic poison, like opium and like alcohol, though usually in a less degree".