Je vais te donner quelques idées vite fait:
Fast food or know also as junk food as known a big impact and sucess during this late years due to a society who consumes a lot, an increase of people who work outside so they can't eat at home. But it can be really toxic and bad for our health. For example, if we compare a healthy salad with pizza, surely is not the same thing, regarding the quality and the nutriments in each one. Eating a salad a lot of times won't make you ill, in the contrary, in the case of eating pizza often that can cause illness, gaining more weight, being more lazy to do sports etc.
Fast food can be delicious but it's not positive for our physical health and mental health either.