white hairs can be due to many reasons like lack of nutrition, genetical and may be your nature. Your over weight is also should be checked though it is not directly related to the greying of hair. but over weight and greying of hair represents improper assimilatiaon and absroption of nutrition. check your thyroid functions. also do exercises and avoid spice foods, salt, junk foods. Not just providing the body essential elements will solve the issue. your body should be in a position to absorb them. eat only when u r hungry.eat more frutits except banana, mango, chikoo and vegetables.
apply belleric seed oil (baheda oil) as hair oil and also as nasal drops. but before starting the treatment try consult a good ayurvedic physician.