There are two ways you can think about 80/20 eating. One: eat healthy 80% of the time and save 20% for splurges. That's great because it stresses how eating is not about perfection, and as we mentioned earlier, how it can be pleasurable, too. However, what does that really look like? That might mean having a 150-calorie treat daily, like Schapiro does, or saving it all up for a big meal out on the weekend. Make it work for you rather than stressing out about percentages.
It's trendy to think "food should be fuel" or that food is something that helps you lose (or, ahem, gain) weight. But thinking only in terms of number on the scale takes away a huge part of what eating is about: pleasure. "If you think of eating as something enjoyable and something you do without guilt or without judging yourself, and you stay active, you're less likely to overeat, have a better diet, and maintain any weight loss for the long haul," says Zied. It's true: feeling guilty about your food choices can undermine weight loss—and even pack on the pounds—while a celebratory mindset gives you more control over your diet and can thwart weight gain, found a 2014 study in the journal Appetite.
Juice diets do prevent your body from going into a state called ketosis, he says. Ketosis means your body has no carbohydrates to burn for energy, so it has to burn stored fat or whatever else is available, he tells WebMD. "You feel bad, even smell bad. That's what makes you feel like hell during a [water-only] fast. But is that because the toxins are coming out? No! You're going into ketosis. It's known physiology."