Functional medicine proponents say that it focuses on interactions between the environment and the gastrointestinal, endocrine, and immune systems. Practitioners attempt to develop individual treatment plans for people they treat.
Functional medicine significantly departs from mainstream medicine in its emphasis on treatments and concepts of health and disease which are not currently known to be effective or which have been shown to be ineffective by clinical research. These include
- Orthomolecular medicine 
- Detoxification of undocumented toxins.
- "Biochemical Individuality" (i.e. the notion that the nutritional needs, chemical constitution and disease states are unique for every individual; this represents a recrudescence of the mainstream medical conception of disease common before the development of germ theory)
- Promotion of the discredited link between MMR vaccine and autism (the retracted Lancet paper by Wakefield et al. is cited in The Textbook of Functional Medicine)
- Organ reserve
- Diagnosis of chronic occult infections (e.g. chronic Lyme disease)
- Homeopathy, including "Biopuncture", the injection of homeopathic remedies
- Dubious nutritional interventions, including avoidance of gluten
Functional medicine typically seeks to provide chronic care management based on the assumption that "diet, nutrition, and exposure to environmental toxins play central roles in a predisposition to illness" and "provoke symptoms, and modulate the activity of biochemical mediators through a complex and diverse set of mechanisms."
The Institute for Functional Medicine
Jeffrey Bland and Susan Bland founded the Institute for Functional Medicine (IFM) in 1993.
In 1991, the U.S. Federal Trade Commission charged that two corporations led by Jeffrey Bland, HealthComm and Nu-Day Enterprises, had falsely claimed that their diet program could cause weight loss by changing consumers' metabolism and cause them to lose weight without exercising so that fat would be lost as body heat instead of being stored. In 1995, the FTC charged Bland and his companies with violating the 1991 consent order by making further unsubstantiated weight-loss claims for several products, including the UltraClear dietary program, which had been falsely claimed to reduce the incidence and severity of symptoms associated with gastrointestinal problems, inflammatory and immunologic problems, fatigue, food allergies, mercury exposure, kidney disorders, and rheumatoid arthritis. The second settlement agreement included a $45,000 civil penalty.
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