Yes and no.
Hair loss in cancer patients is typically caused by the cancer treatment, not the disease itself.
Chemotherapy, radiation, and other treatments commonly result in differing degrees of hair loss.
As the drugs destroy cancer cells, they also harm the hair follicles, leading to hair loss.
Short answer:
No, cancer does not cause it, the treatment does.
Worry less about the amount of calories and more about how. so consider options such as exercising and eating well balanced meals without bad ingredients. try to find organic foods (usually they will have less surgar) don't avoid carbs completely but limit intake. basically get into healthy eating and regularly exercising to help loose weight. don't focus on the numbers just make your body feel happy. :)