Junk food is just what it sounds like: food with little or no nutritional value—mainly fast food and packaged snacks that contain high amounts of sugar and unhealthy fats. Along with contributing to rising obesity rates, junk food may be destroying the healthy bacteria in our guts that make up at least 70% of our immune system. This data comes from a study conducted by Tim Spector, a professor of epidemiology at King’s College London and author of the book, The Diet Myth.
Spector did an experiment to see just how an unhealthy diet affects the gut. He asked his 23-year-old son Tom to spend 10 days eating nothing but fast food burgers, fries, chicken nuggets, and cola. Fecal samples were taken both before and after the experiment to measure gut bacteria diversity.
Even though Tom started out with around 3,500 bacterial species in his gut, that number shrank to 2,200 after not even two weeks on a predominantly fast food diet. That means he lost roughly 1,300 species—including half of his beneficial Bifidobacteria—and his gut diversity was drastically reduced. And, while he stuck it out to the end, Tom admits feeling lethargic and ill just three days into the study.
Thankfully, Spector points out that we can shift back toward a healthy balance by way of a varied and healthful diet. By cutting out junk food and swapping sugar, starchy carbs, and unhealthy fats for a diet rich in non-starchy vegetables, low-sugar fruits, fermented foods, healthy fats, and protein, experts believe we can increase gut bacteria diversity and promote optimal well-being.