Smoking and tobacco-related health complications are the single largest cause of preventable, premature death. A smoke can cost the life of a loved one so Stop Smoking, don't delay it. Your weight is alot under Ideal weight for your height But if you are healthy and you can perform regular activities without any problem and are disease free you should be Ok. Please consult a Nutritionist for a weight gaining diet. And also check the following link for Nutritional information. https://www.webindia123.com/health/diet/calorie/weight.htm