Most nutritionists will tell you thereâs no food you should never eat, but obviously there are lots of foods you should eat very rarelyâfried Oreos, anyone?. Diets that forbid macronutrients wholesale, like carbs, tend to be unsustainable long-term. In the case of carbohydrates, theyâre essential for providing energy, among other things. Sure, you can ditch anything for a week or two and probably be okay. But if thatâs the main reason youâre losing weight, as opposed to cutting calories elsewhere or learning to downsize your portions, youâll start gaining again as soon you bite into your next bagel.