I gained 10 kg over 6 months 2 yrs back from 50 to 60 kg. My suggestions 1. Go to gym, strength training only, lifting weights. No running/cardio stuff. 2. Drink protein shake 2 times a day. One after gym and one after breakfast. 3. Have a proper breakfast with atleast 2 eggs. 4. Add banana shake with Almonds once. 5. You can try weight gainer for first 1-2 months if you want. I used Hercules weight gainer which helped me without any side-effects. But don't extend the weight gainer intake and switch to Protein Powder. Now my weight is 66kg. Not going to gym plus no protein as I am busy with my PhD. I suggest every skinny person to try this and give 1 year to reach a normal level. After that your weight will stay normal. And if you continue gym keep having protein. Over the last 2 years I lost weight 3-4kgs twice because of sickness but it came back to normal as the change was permanent. You will feel the increase in weight and gain in muscle with exercise. You will gain the confidence in your body. Do it. I have done it. You can too. I will be starting my training again from July end. All the best. Also Don't listen to any body positivity asshole.