Hello.
Considering your height and weight you are under weight. Before attempting to gain weight by the false, harmful, hormonal and advertised products, you must do investigations to find out any cause for under weight. Hereditary plays a major role.
Do basic blood tests like TC, DC, ESR, Hb, Sugar, Thyroid profile and Urine analysis + X-Ray chest PA view.
If you have a low appetite, and frequent diarrhea - find the cause
If any problem is found treat the cause.
Do moderate Gymnastic exercise to maintain your muscle tone and to increase the appetite.
Healthy nutritious + high protein and green vegetable diet is advised.
Protein and Vitamins can be supplemented.
A course of anti amoebic and anti worm treatment can be taken.
Take hygienic diet, plenty of not contaminated water and maintain the time schedule of your diet.
After consultation with your Dr you can have Anabolic steroids - only if absolutely indicated.
Wishing you speedy weight gain,

Hello,
Thanks for the query to H.C.M. Forum.
5'11" weight 58 kg.
Weight in my view is very nice but anyhow you want to increase your weight.
Consider following points.
A person require normally 1500-2000 calories/ day ,if his work is moderate quality.
If work is very hard he requires more than 2500- 3000 calories depending upon the quality of work.
fat ( ghee) contains 9 kcal/gram i.e. 100 gram gives 900 kcal.
protein gives us 5.5 -7 kcal/gms,
carbohydrate 4-5.5 kcal/ grams.

My aim is here to advice you what type of food and how much amount of food will develops deposition of fat in your body.

As for example ,if you eat 4500 kcal/day within 3 months fat will deposit in your body.
As extra calories which we take in the food ( other way ) deposits in the form of fat in body.
First of all it starts from belly ( over abdomen).
Still in my opinion your weight is balanced so no need of any extra weight.
If you want to increase it than take food as mentioned above.
Hope you will take a good decision.
Good luck.
Dr. HET