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If you religiously eat kale salads and acai bowls during the week but think it’s OK to binge on pizza and wine all weekend long, it might be time for a little reality check. A new study from the University of New South Wales (UNSW) suggests that whole-weekend binge eating may be just as bad for your gut microbiome as a regular diet of junk food. Furthermore, the study found that yo-yo dieting reduced the number of microbial species capable of metabolizing flavonoids, which aid in weight loss and help protect neurons in the brain. In the study, lead researcher Margaret Morris, the head of pharmacology at UNSW, fed rats either a healthy diet of “chow” (low-fat rat food) or a diet of cafeteria food. The rats in the cafeteria-food group were fed foods like cakes, meat pies and dim sum three days per week but ate low-fat foods the other days of the week.
Science has already shown that eating unhealthy foods can lead to a disruption in normal gut bacteria, which has been linked to conditions such as inflammatory bowel disease and obesity. But what we didn’t already know, as UNSW researchers point out, is that eating badly even three days a week is enough to alter the gut microbiota toward the pattern seen in obese rats. Though further study on humans is needed, Morris says that if you’re generally eating a healthy diet of fruits, vegetables and good-quality proteins, then the occasional splurge should be fine. “It is likely that the occasional treat like a slice of cake or half a pizza, if consumed once a week, would not have enormously detrimental effects on the gut microbiota,” she says. So to avoid reversing the effects of healthy weekday eating, keep your clean-eating lifestyle on track – even on the weekends. Instead of two days of indulging, strive for two treats instead!