whether or not your hair loss is related depends on how rapidly you are losing weight. if you are crash dieting or using a fad diet for rapid weight loss you may indeed have a caloric deficiency which is translating to hair loss. i recommend that you lose the weight slowly and in a controlled fashion (1 pound per week) and be sure to maintain good nutrition while you're dieting.
i'm dieting to lose weight and my hair is falling out. could my diet be causing my hair loss?