Metabolic typing

Metabolic typing is the term for a diet based upon the concept that people have unique metabolisms, and that therefore the nutrients and their balance which are appropriate for one person may be inappropriate for a second, and detrimental for a third.

Proponents of metabolic typing claim that different populations have different types of metabolism, and that diets should be tailored to reflect these purported differences. Metabolic typing claims to use common visible symptoms related to the skin, eyes, and other superficial parts of the body to assess different aspects of a persons metabolism and categorize them into broad metabolic types. In addition, some proponents of metabolic typing use controversial or unproven tests such as hair analysis to determine a person's "metabolic type".

A number of somewhat different "metabolic typing" diet plans are currently marketed by a number of entrepreneurs. The validity and effectiveness of metabolic typing have not been established.

Background
Metabolic typing was introduced by William Donald Kelly, a dentist, in the 1960's. Kelley advocated basing dietary choices on the activity of one's sympathetic and parasympathetic nervous systems. In 1970, Kelley was convicted of practicing medicine without a license, as he had diagnosed a patient with lung cancer based on a fingerstick blood test and prescribed nutritional therapy. He continued to promote a metabolic typing diet through the 1980's.

Effectiveness
Although metabolic typing diets have been promoted to patients with cancer, the American Cancer Society states that:

The Memorial Sloan-Kettering Cancer Center website notes that "...retrospective reviews of the Gerson, Kelley, and Contreras metabolic therapies show no evidence of efficacy."

Some metabolic typing companies use a battery of established blood and urine tests performed by reputable laboratories, but interpret the results in an unconventional and medically unsound fashion. During a 1985 investigation into one such firm, an investigator sent 2 separate samples of blood and urine for analysis; he received 2 drastically different "metabolic typing" reports and dietary plans. Both plans involved the purchase of dietary supplements costing several dollars per day.