Hello,
Most likely it looks like malnutrition which can be responsible for the hair fall. Other causes could be due to stress, fungal infections, alopecia aereata, hormonal imbalance (overproduction of dihydrotestosterone and thyroid hormones irregularities),malnutrition, telogen effluvium and sebum plugs on skin.
I would suggest you to consult a dermatologist and get these possibilities evaluated. It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
We normally lose 50 - 100 hair strands per day. If there is more hair loss than this, the first cause we look at is diet. It has been long known that anorexia causes hair loss. Your 400 calories on alternate days is flirting with an anorexia-like diet and is most likely stressing your body. Rather than cut your long locks, look to have a balanced diet each and every day. Good luck.