When your diet is going well, it's the best feeling in the world. But there's one habit that you need to quit. Find out from our friends at Shape [1].

It's a familiar scene. You've been good with the quinoa bowls and kale salads all week long and want to let loose on that plate of nachos come Friday night. (We suggest these junk foods that are actually good for you [2].) Indulging after your healthy week of munching can't be that bad, right? New research from the University of New South Wales in Australia [3] begs to differ.

The study, which was published in the journal Molecular Nutrition & Food Research, examined the effects of "yo-yo dieting" (aka keeping a healthy diet through the week and bingeing on the weekends) on overall health. And it found some interesting implications for your gut.

The human gut is made up of 100 trillion microbial cells that ultimately influence your metabolism, nutritional absorption, and immune function. Disruptions in your diet may impact these cells, leading to issues like inflammatory bowel disease and obesity. Yeah, it's pretty important to keep those babies healthy.

The researchers studied how limited junk food bingeing affected the gut microbiota in three groups of rats. One group was given unlimited access to a "junk food" diet; the second was given a healthy diet four days a week and junk food three days a week, and the third group ate healthy all the time. Researchers tracked body weight, fat mass, insulin levels and leptin (the hormone that regulates hunger and satiety) over the course of 16 weeks.

They found that the microbiota of rats that ate healthy most of the time (but not all the time) was basically the same as those that ate junk seven days a week. And both groups had markedly worse gut health than the full-time healthy eaters. The rats who cycled between healthy days and junk days also consumed 30 percent more overall.

Uh, worst news ever? Don't worry. It's important to note that the study tested what three full days of eating poorly did for gut health, so allowing yourself a few jalapeño poppers here and there might be OK. Just remember to get back on the bandwagon after nacho night, and see how to splurge and still lose weight [4].

Check out more great stories from Shape:

• Which Matters More: Exercise or Weight? [5]
• Should You Really Hate on Processed Foods? [6]
• Bone Broth Has Officially Gone Mainstream [7]