Infectobesity

The term "infectobesity" refers to obesity of infectious origin and the emerging field of medical research that studies the relationship between pathogens (disease-causing organisms, such as viruses and bacteria) and weight gain. The term was coined in 2001 by Dr. Nikhil V. Dhurandhar, at the Pennington Biomedical Research Center. (Dhurandhar, 2001).

Bacteria
The study of the effect of infectious agents on metabolism is still in its early stages. Gut flora has been shown to differ between lean and obese humans. There is an indication that gut flora in obese and lean individuals can affect the metabolic potential. This apparent alteration of the metabolic potential is believed to confer a greater capacity to harvest energy contributing to obesity. Whether these differences are the direct cause or the result of obesity has yet to be determined unequivocally.

Viruses
An association between viruses and obesity has been found in humans as well as a number of different animal species. The amount that these associations may have contributed to the rising rate of obesity is yet to be determined.

The fat virus is the popular name for the concept that some obesity in humans and other animals has a viral source. The AD-36 adenovirus has been observed to increase the amount of body fat on laboratory animals, an effect that has been duplicated on chickens and monkeys.

Ad-36 is know to cause obesity in chickens, mice, rats, and monkeys and was present in 30% of obese humans and 11% of nonobese humans. The prevalence of Adv36 positivity in lean individuals increased from ∼7% in 1992-1998 to 15-20% in 2002-2009, which paralleled the increase in obesity prevalence.