tape measureIn this week’s issue of the journal Nature, researchers at the Washington University in Saint Louis reported on bacteria and their contribution to obesity. The mouse studies indicated that certain bacterial species were more abundant in obese mice than their lean counterparts. The “obese” bacteria were also found to harvest energy from food more efficiently with less calorie content excreted as waste. Bacterial flora from obese and lean mice were introduced in “germ-free” mice, and mice with the “obese” microbiota experienced a significantly greater increase in body fat. The group had published a related study several years ago, so the idea is not completely novel. On the other hand, it is an interesting concept that has not yet reached common knowledge.

Before anybody blames their gut bacteria as the source of obesity, recall that the study was performed on mice. The findings may or may not translate to humans. The authors describe a related study (Webb et al.) that involved human subjects. Obese individuals were noted to excrete less fecal energy than lean subjects. Although the results were not statistically significant, more research is still needed before discounting bacterial involvement in human obesity. Let us also remember that obesity results from a combination of factors. Dietary intake, physical activity, and genetic composition strongly influence body weight. In the study, the authors equalized food consumption among groups to minimize this possible confounder. Five Big Macs in the mouths of “lean” mice can still produce more weight gain than in “obese” mice fed peanuts.

The implications of the study are fascinating. Consider the potential for future gut therapy (e.g., GoLytely and antibiotic bowel prep, followed by customized bacterial inoculation) to treat obesity or promote weight loss. Time to file my patent!

  • Sources
  • Turnbaugh PJ, Ley RE, Mahowald MA, Magrini V, Mardis ER, Gordon JI. An obesity-associated gut microbiome with increased capacity for energy harvest. Nature 2006;444:1027-31.
  • Backhed F, Ding H, Wang T, Hooper LV, Koh GY, Nagy A, Semenkovich CF, Gordon JI. The gut microbiota as an environmental factor that regulates fat storage. Proc Natl Acad Sci U S A 2004;101:15718-23.
  • Webb P, Annis JF. Adaptation to overeating in lean and overweight men and women. Hum Nutr Clin Nutr 1983;37:117-31.

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