I have an answer to your weight gain that may not have been considered. Remember it may not be the only answer. Probably you were given Antibiotics. Antibiotics are given to animals to fatten them and cause weight gain.

I personally suspect that the principal issue in the modern epidemic of obesity is actually modern industrial farming. The process strips the food of base nutrients like trace minerals and produces a food which causes malnutrition. Canada has studied this in depth and the data is there. The varieties of foods as well have been altered for this purpose of causing more food demand. Modern Agricultural banking will not fund alternative methods and varieties.

The basic fact is that animals will not given a balanced diet overeat and become fat in any real quantity. This imbalance of diet is deliberate in modern fatening operations for farming. The cows will never get fat like they do in a feed lot if given a natural decent diet. This fact is plain for the issue of fat people as well. Given what is essentially a feedlot diet they get fat.

No doubt infections do influence this as well. The other posts on this forum remarking on hygene also are very realistic. This is a complex problem set.