\n\nStarting a new diet or fitness regimen is always tough, but most would agree that number one thing that helps people stay on track is seeing results. It can be weeks before seeing progress if you’re trying to lose weight or gain muscle – but how long before that new diet reduces your risk of disease?\nJust 3 days, as research suggests. A 2013 study by microbiologist and professor Lawrence David of the Duke Institute for Genome Sciences and Policy suggests the gut microbiome changes rapidly in response to meal choices. Although we’ve always known that our health changes based on the food we eat, this study proves that when we consume certain foods, our microbiome changes incredibly quickly - starting just hours after a meal. This is more important than ever as awareness grows of the critically important role of our gut microbes in determining our general health, weight, and risk for diseases including diabetes, coronary artery disease, arthritis, and even cancer.\nDavid’s study consisted of 10 volunteers that switched to either a (high fiber) plant- or animal-based diet for 5 days, with the former avoiding animal products and the latter eating conventional milk, cheese and meat. The researchers then scrutinized how their gut bacteria responded to the change in diet.\nWithin 3 days, bacteria known to tolerate high levels of bile acids increased significantly in the meat-eaters. (The body secretes more bile to digest meat). These 5 participants also experienced the most dramatic changes in their bacterial community, with 22 animal-specific microbial species found in their microbiomes along with a decrease in the beneficial bacteria that are necessary to metabolize complex carbohydrates.\nAlterations in gut bacteria were less extreme (but more beneficial) for those who consumed more plant-based foods. While the bacterial changes were not as extensive every time they ate a meal, a small number of additional species of beneficial bacteria settled in their gut. These findings opposed those of the meat-eating group who saw a reduction in certain bacterial species throughout the course of the study.\nAnother study by Tim Spector, professor of genetic epidemiology at King’s College London, followed a subject that ate only McDonalds for 10 days (Big Mac or Chicken nuggets as well as fries and Coke). The results showed that the subject lost around 40% of his bacteria species, about 1,400 types! \nThese studies affirm that eating a fiber rich plant-centric diet can encourage bacterial diversity. Dietary fiber serves as food for many of the bacteria that live in our guts while too little fiber can starve the bacteria we want to keep around. As Professor David himself put it, “It’s very difficult to read the literature and not eat more fiber.”\nSo if you’re feeling sluggish after the holidays or an especially indulgent weekend, take comfort in knowing that you (and your microbes!) can be back on the right track in just a few days.