On this diet, cake isn't just okay—it's expected.

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You've probably heard of people who follow the 80/20 rule. Many celebs swear by it: Jillian Michaels has said she follows an 80/20 eating plan, as does Miranda Kerr and Jessica Alba. Australian chef Teresa Cutter even wrote a book about it.

We can see why this diet has so many famous fans. Quite frankly, it sounds pretty sweet. Instead of following a perfectly "clean" diet, you’re encouraged to eat healthy 80% of the time. In other words, you can eat well during the week but give an enthusiastic yes (sans guilt) to that burger you've been craving on the weekend.

But is the 80/20 rule too good to be true? And will eating less-than-healthy foods 20% of the time sabotage your weight loss efforts? We tapped registered dietitians to get their take.

Is it healthy?

It can be. Following an 80/20 diet can help you maintain a balanced mindset about eating, experts say. “Being healthy doesn’t require eating 'perfectly'—whatever that might be,” says Rachael Hartley, RD, a dietitian at Avocado A Day Nutrition LLC and co-founder of the Joyful Eating, Nourished Life program. “If 80% of your diet consists of nutritious whole foods, there’s room for the other 20% to come from fun foods without compromising health,” she says.

Also good: Knowing you can occasionally indulge in an ice cream sundae or to-die-for Italian pasta meal will make you more motivated to stick to healthy habits at other times, notes Chicago-area dietitian Christine Palumbo, RDN.

The downsides

“We are notoriously terrible at counting calories, estimating portions, and assessing how much we really eat,” says Samantha Heller, RDN, author of The Only Cleanse and a SiriusXM radio host. “So it makes sense that we wouldn’t be very good at estimating what 20% of our diet is."

It's also important to consider how you categorize the foods that fall into that 20% category. Labeling chips or brownies “bad” can ultimately make you feel guilty about your choices—and that’s the exact opposite of what 80/20 should do for you. The word "cheat" "implies that healthy eating is punitive," Heller points out.

Ultimately, know that indulging has a place in any sane eating plan. “While the 20% may not be contributing much nutritiously, these foods can be nourishing in other ways,” says Hartley. Namely, how a cheese plate with the girls is exactly what you need on a Friday night. Or how that double scoop totally feeds your soul.

How to try it

For the 80%, fill your plate with fresh, whole foods like veggies, fruit, whole grains, legumes, nuts, dairy, lean meats, and fish. Your 20% can be any food you want, though it's best to stick to foods you truly love. Those treats will give you the biggest boost of satisfaction.

The way you go about it depends on your personality. If you want more structure, Palumbo suggests allowing yourself four freebie meals throughout a given week, or one full day plus an additional meal. You can also eat nutritiously most of the time and fit in one or two small indulgences a day.

But you can also be more lax and consider 80/20 a general guideline rather than a rule. Hartley is a big proponent of intuitive eating—listening to your body, feeding it nutritious foods most of the time, and following your intuition when indulging. She says that eating like this tends to naturally shake out to 80/20 without really thinking about it.

If you’ve tried 80/20 and find you go crazy with “cheat” days or meals and you’re not seeing the results you want (hello Mexican meal with margaritas, guac, enchiladas, and ice cream for dessert), Palumbo recommends aiming for 90/10. “Often 80/20 leaves too much leeway for indulgences, whereas 90/10 is pretty strict but does allow for a few,” she says. You can look forward to two freebie meals per week, and this method reduces the risk of overeating. “You can easily consume hundreds of calories in a few minutes, which can negate all of your hard work,” she says.

No matter how you approach it, the message is clear: let them eat cake—in moderation, of course.