Diets Engineered to Work With Your Microbiome Are Latest Startup Craze

Nancy Holloway has been on a diet all her life. She has tried them all, losing weight and then gaining it back, at one point weighing 300 pounds.

Four months ago, though, she began a diet based on an analysis of her microbiome, the trillions of microorganisms in her gut. Now, she says she is losing 5 pounds a month.

Ms. Holloway says on the diet she has found avocado, frowned upon on many other weight-loss plans, “is the perfect food for my body.” Fresh fruits and vegetables no longer make her feel sick.

“It’s insane,” says Ms. Holloway, a 70-year-old retired nurse and a participant in the long-running Nurses’ Health Study at Harvard University. “If you feed your body what it wants, it will take care of all those calories, and you don’t have to worry about them,” she says.

A crop of “precision nutrition” startups are racing to develop and engineer individualized diet programs, based on growing evidence that people’s gut microbes—even those of identical twins—respond to food in significantly different ways. The studies reflect the belief among many scientists that more finely-tuned nutrition could help curb the nation’s chronic-disease epidemic.