Weight Gain After Appendix Removal, Have High Metabolism Rate. Is This Related ?

Hello. I had my appendix taken out two days ago, and am now experiencing weight gain . I should explain i am 23 years old and have a very high metabolism . I have tried repeated times in the past to put on weight, such as weight gain supplements , having bigger meal, having 4 meals a day, etc., but nothing has ever worked. I am 9 stone and 6ft 2ins and have had a low BMI for many years through no choice of my own. But now two days after surgery without trying i have put on weight like i have never been able to before. I find this a blessing in disguise, but just want to make sure this is normal, healthy, and that if my metabolism is changing because of this appendicetomy, it won t go from one extreme to the other and become to slow. Thank you.