You need fats and which ones you consume matters a great deal, exclusively consuming canola oil or soybean oil is bad. Refined oils are worse that non-refined or virgin oils, high heat makes oils unhealthier, this depends on the type of oil.
Protein is useful if you want to facilitate muscle growth. In this case it’s smart to increase the amount of protein in your diet.
You need a lot of different micro nutrients (vitamins and minerals) to sustain yourself, not consuming these (or their precursors) will lead to serious medical issues or death.
One can develop some level of insulin resistance if ones diet improperly influences blood sugar levels and this is bad.
Consistently eating too much or too little calories is bad.