Thanks for the query.
Crash diets are one of the commonest cause of hair fall
Hair follicles dont get enough nutrition and start falling.
This is called as telogen effluvium
If you want to continue with crash diet,
Take nutritional supplements in the form of tablets.
Please meet a dermatologist
for exact diagnosis.
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.