Healthy food is a way of eating that should give priority to the vitamins and minerals in raw and cooked vegetables and fruit. It is also vigilant about the fertilizers and pesticides used to grow them. Meat must be traceable and the animal must have lived and be fed decently from birth to slaughter without pain.
Each food taken separately can be healthy, it is its association with another that can be problematic. Mashed potatoes and lentils, for example, are not a representation of a balanced meal.
To be balanced, the meal must contain protein, fat, starch, fiber and vitamins. You can combine two elements for one meal and two on top of another, but you must not make the mistake of marrying in the same plate a simple duo: starchy food and protein for example. This association is not dangerous in itself, but it could quickly lead to constipation or weight gain to a greater or lesser extent.