How to gain weight naturally when you have high metabolism rate? I am 26 year old girl but I am underweight. My haemoglobin level when last checked was 13 and BP was 120/80. No thyroid found when checked last time and all the other tests were also fine. I am thin since the age of 9-10 years and not been able to gain weight despite eating 4 times a day. My daily food consists mostly of carbohydrates since I eat rice twice a day along with good amount of proteins like rajma, beans etc. I also take fruit juice almost 4-5 days a week and sometimes fruits. I have tried eating dry fruits and peanut butter as well to increase weight but its of no use to me. Can you please suggest something so that I can gain weight fast.