So people like to eat out, and when they do, they prefer mushy, fiber-free comfort foods. But that’s a pretty dangerous road to go down.

As my colleague Ed Yong has written, low-fiber diets make gut bacteria more homogeneous, possibly for generations. Mice that are fed high-fiber diets have less severe food allergies, potentially because gut bacteria break down fiber into short-chain fatty acids, which support the immune system. A more recent study in mice found that a low-fiber diet can spark inflammation in the intestines. We still need more studies to understand exactly how fiber and the microbiome interact in humans. But we do know that hunter-gatherer communities in Tanzania and elsewhere, who don’t eat Western diets, eat about 100 grams of fiber a day and have much more diverse microbiomes than Westerners.

“We’re beginning to realize that people who eat more dietary fiber are actually feeding their gut microbiome,” Justin Sonnenburg, a microbiologist at Stanford University, explained to NPR.

There are also already plenty of other studies detailing the many ways fiber boosts health.

Behold, an extremely confusing flow chart, from a 2005 study, showing how fiber leads to greater satiety, less insulin secretion, and more short-chain fatty acids, which all amounts to one thing: less body weight.

People who are obese consistently report eating less fiber than people who aren’t. Even after controlling for other factors, fiber intake is inversely associated with body mass index. Eating more fiber helps overweight people lose weight and body fat. It’s been shown to reduce breast-cancer risk by reducing estrogen levels in the blood and to promote healthy aging.

“We found that those who had the highest intake of fiber or total fiber actually had an almost 80 percent greater likelihood of living a long and healthy life over a 10-year follow-up,” Bamini Gopinath, from Australia’s Westmead Institute, told PsychCentral. “That is, they were less likely to suffer from hypertension, diabetes, dementia, depression, and functional disability.”

So, if you are the kind of person who does Drynuary—in other words, you just want to be a little bit healthier without completely revamping your entire life—just try to eat more fiber.

The best part about this health advice is that it doesn’t involve eating something you don’t like. Fiber is in almost every fruit, vegetable, and whole grain. You could eat more apples and celery, sure, but there’s also fiber in things like corn tortillas, beans, grainy bread, and some types of breakfast cereal. A Chipotle burrito with brown rice and corn salsa will get you 22 grams of fiber, compared to just three grams in a Big Mac. (The burrito also has more than twice as many calories, though, so, you know, exercise caution as you would in all things.)

But you don’t have to stop eating anything you do like: People lose about as much weight just by eating a lot of fiber as they do on complicated diets, even if they eat slightly more calories in the process.

So this coming Graintember, just order the peas as your side instead of the mac and cheese. Just cut a banana up over your Corn Flakes, which are surprisingly not fibrous in their own right. Just eat more fiber.