Although sugary and fatty foods can’t inherently cause harm to someone if they’re part of a varied, balanced diet, it can be harmful to someone’s health in the long run if all they eat is— say, ice cream or processed snacks. This is due to the fact you may not be getting all the nutrients and minerals you need, so you may end up malnourished. If you don’t get enough vitamins or nutrients you may feel tired, sluggish, etc. in addition not eating a balanced varied diet can cause: abnormally high or low blood sugar or blood pressure, irregular blood levels, unhealthy weight loss or weight gain, irregular hormones, and it can mess with somebody’s mood a lot.