Processed carbs and sugars are always unhealthy. Carbs from vegetables are good though. You can’t overeat vegetables.
The more processed a food, the worse it is for you. Your body treats wheat flour the same way it does sugar. Scientists are discovering that wheat (in any form) is actually really bad for us. And is one of the main catalysts for all our metabolic diseases like diabetes, heart disease, and stroke.
Eating refined sugar regardless of your diet is unhealthy - this is pretty much the one thing all dietary philosophies agree on. In the context of IF/OMAD it would likely result in longer fasting periods being necessary to accomplish the same effect you’d get from doing it on low carb/keto/carnivore.