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The high-fat, very low-carb ketogenic diet first emerged in the 1920's as an epilepsy treatment, but only recently started gaining popularity as a weight-loss plan. While keto dieters tout promising benefits like quick weight loss and increased satiety—all while eating as much cheese and bacon as they want—there's one thing that's often overlooked: gut health.
You (probably) know how important it is to maintain a healthy gut microbiome; the good bacteria in our gut can positively affect our weight and even keep chronic diseases at bay. And more research says that our gut health—and overall health—is largely tied to what we eat.
"I get very frustrated when I see claims on the internet that the keto diet is good for your gut health. There's not one single study to support that. In fact, the studies that exist suggest that keto decimates the gut," said Dr. Bulsiewicz.
Here's why: Dr. Bulsiewicz says most people in the U.S. have somewhere between 300 to 1,000 different species of bacteria living in our guts, and that bacterial diversity is necessary for good health. Bulsiewicz says, "When people lose or reduce the number of bacteria species in their gut, they can develop diseases such as ulcerative colitis, Crohn's disease and inflammatory bowel disease."
A study published in Nature found that participants who ate a diet high in animal products (such as eggs, meat, and dairy) for just five days experienced significant growth of the gut bacteria associated with IBS. Dr. Bulsiewicz says that by eating a ketogenic diet "you may not have IBS yet, but you're already laying the foundation for it."
When you eat a keto diet, you're eliminating nearly all carb-containing foods, including those good-for-you, fibrous foods like fruit, veggies and whole grains that support your microbiome. The largest gut health study to date, called the American Gut Project, surveyed over 11,000 people and found the number one predictor of a healthy microbiome was the variety of plant foods consumed in one's diet. Dr. Bulsiewicz says, "When you restrict the diversity within your diet, you are also restricting the diversity of your gut microbiome, which causes disease."
According to the American Gut Project's findings, we should all be eating 30 or more different plant foods each week for optimal gut health. (Yep, you read that right!) While that would be one very expensive grocery trip, you can look for other opportunities to boost your plant-food intake by loading up on various fruits and veggies at the salad bar, making your own mix of nuts and seeds at the grocery store bulk bins, and opting for whole grains over refined whenever possible.
Not quite sold on reintroducing carbs to your diet? Dr. Bulsiewicz says, "Carbohydrates aren't bad; refined sugar, processed grains, and ultra-processed foods are bad. I support cutting those out 100 percent, but I don't support cutting out carbs."
Dr. Bulsiewicz also recommends that, for losing weight, the key is adding foods to your diet, not taking them away. He points to a recent study that showed a completely unrestricted plant-based diet (one where you can eat whenever you're hungry), helped participants lose 14 pounds on average.
The bottom line
If you want to lose weight, the key isn't going keto or cutting out an entire food group (unless your doctor has specifically advised you to). To shed pounds, aim to cut out ultra-processed, refined carbs and add in more fiber-containing foods like fruits, vegetables, and whole grains. Your gut will thank you!