Infectobesity: don't catch it

Posted on Fri, 24 Jul 09

“Infectobesity” sounds like an unlikely cause of weight gain but increasing evidence suggests that infectious organisms such as viruses and bacteria may contribute to the development of overweight and obesity [1]. Person-to-person contact has been linked to the spread of obesity through social networks [2] and a candidate infectious organism may be closer to you than you think. 

Deep inside your digestive tract there is an immense amount of bacteria, in fact they collectively weigh over a kilogram and outnumber cells in the human body tenfold [3].  Recently it was discovered that the gut bacteria of obese and lean individuals is distinctly different and that the unique bacteria inhabiting obese people is more efficient at extracting energy from food and depositing it as fat [4].

A remarkable study published in the journal Nature found that mice infected with gut bacteria from an obese mouse subsequently had a much greater increase in body fat than infection with gut bacteria from a lean mouse [5]. This finding raises the possibility of obesity being, at least in part, an infectious disease.

Whether obesity promoting gut bacteria can be passed from person-to-person is unknown. However, it is known that an overgrowth of “bad” bacteria in the gut, termed dysbiosis, may be caused by a diet low in fibre, excessive alcohol consumption, antibiotic use or even chronic stress [6]. Strategies that can increase “good” bacteria in the gut while decreasing levels of bad bacteria include increasing dietary fibre intake and the use of probiotic supplements [7].

There is some evidence from human studies to suggest that increasing dietary fibre intake [8] and perhaps even using a probiotic supplement [9] may help maintain a healthy body weight by improving the health of your gut bacteria. Avoiding high fat and sugar foods and consuming more unrefined foods from plants such as nuts, seeds, vegetables and fruits while minimising stress and using antibiotics sparingly may improve the health of your gut flora [6].

Image: Lactobacillus, a human gut bacteria. 

References

1. Pasarica M, Dhurandhar NV. Infectobesity: obesity of infectious origin. Adv Food Nutr Res. 2007;52:61-102.

2. Christakis NA, Fowler JH. The spread of obesity in a large social network over 32 years. N Engl J Med. 2007 Jul 26;357(4):370-9.

3. Guarner F, Malagelada JR. Gut flora in health and disease. Lancet. 2003 Feb 8;361(9356):512-9.

4. Tsai F, Coyle WJ. The microbiome and obesity: is obesity linked to our gut flora? Curr Gastroenterol Rep. 2009 Aug;11(4):307-13.

5. Turnbaugh PJ et al. An obesity-associated gut microbiome with increased capacity for energy harvest. Nature. 2006 Dec 21;444(7122):1027-31.

6. Hawrelack JA, Myers SP. The causes of intestinal dysbiosis: a review. Altern Med Rev. 2004 Jun;9(2):180-97.

7. Rastall RA et al. Modulation of the microbial ecology of the human colon by probiotics, prebiotics and synbiotics to enhance human health: an overview of enabling science and potential applications. FEMS Microbiol Ecol. 2005 Apr 1;52(2):145-52.

8. Cani PD, Delzenne NM. The role of the gut microbiota in energy metabolism and metabolic disease. Curr Pharm Des. 2009;15(13):1546-58.

9. Woodard GA et al. Probiotics improve outcomes after Roux-en-Y gastric bypass surgery: a prospective randomized trial. J Gastrointest Surg. 2009 Jul;13(7):1198-204.