In a world where nutritionists have lost their minds - they can't even agree in what a vegetable is - it's smarter just to throw the whole concept out and eat a balanced diet without spending $20 on a book. It used to be saturated fats were bad, then trans fats that replaced them were and now butter is back in fashion. Pick any food - except for vegetables, of course, more on that in a moment - and the cycle is repeated. Pick any year recently and you can find Dr. Oz claiming it is a miracle product - acai berries, chocolate, wine, etc.
How is it possible? It's because any field where Dean Ornish and that guy who came up with the Paleo Diet and that guy who claims to be a Yogic Flying Instructor claim legitimacy is not a real field, it is instead an area where data dredging people's memories attempts to pass for science.
Which is more believable to you?
Find two curves, like one curve showing Woman X is thin and that she eats vegetables, and say the latter caused the former. Good epidemiologists recognize confounding factors, like that lots of other things may be involved in good health, and they recognize that findings based on memories of what people think they ate are mostly wrong.
But they have to sell books every year so the advice must change. Actress Alicia Silverstone will pump breast milk as a health miracle with "otherworldly power" - and she chewed her babies food for them. Dean Ornish needed to mix up his extreme veganism to keep the money rolling in so he added acupuncture. Dr. Mark Hyman will just roll out some new diet for the Clinton family and appeal to authority among the political demographic most likely to buy into anti-science nonsense.
Shake off the mysticism. You can eat a McDonald's diet and get fat or you can eat a McDonald's diet and lose weight. What you can't do is eat any diet and pretend it is going to cure you or doom you if you take it to an extreme. Want to lose weight? Consume fewer calories than you burn. No, sugar is not toxic, not even the high-fructose kind found in honey, and meat is not killing you nor will being a vegan save the planet.
Have some fun, just don't think because nutritionists can't make up their minds that any diet is safe.
Or you can live in a fairy tale where toast is giving you cancer.