Side effects are different for everyone and it widely varies which ones you do or don't have
Hair loss [falling out]
Loss of period (if are female)
Increased chance of infertility
Fainting/dizziness
Severe mood swings
Depr*ssion
Anorexia often can lead to other eating disorders, such as bulimia and binge eating disorder
Weight loss (minor-severe)
Social withdraw
heart problems and failure
Brittle bones and nails
Colder than average on a regular basis due to the lack of fat keeping your body warm
These are all of the ones that I could think of and I hope this helps. Stay safe everyone and please try your best to eat [im such a hypocrite, lol]