This isn’t likely to let us off the hook for diet and exercise. But reseachers at Mayo Clinic Arizona and Arizona State University’s Biodesign Institute say the trillions of bacteria in your gut may play a role in regulating your weight. Mice that lack certain bugs tend to be fatter than their germ-free laboratory counterparts, and exposing lab mice to the germs makes them fatter. How much they eat, and how often they hit the exercise wheel, don’t seem to have an impact.

What about people? One study of children from birth to age 7 found:

The children who were normal weight at age 7 had distinctly different bacteria in their [stool] samples than those collected from overweight-obese children, suggesting that differences in the composition of the gut microbiota precede overweight-obesity.

The usual caveats apply: The bacteria/obesity connection has yet to be proved, and more research is needed before this leads to obesity treatments. SFnal scenarios about genetic engineering, nanotech, weight regulation, or gypsy curses are good to go.

[Illustration: deletem3]