What is in our food that is making health-conscious people that were always thin so big now?

Many things: This question does not have a simple single answer as everyone is different. Some people gain weight eating healthy foods because it is the wrong thing for their body. However, msg in so many foods does contribute to obesity. So does high fructose corn syrup. Too many calories in cheeses and meats...Some may have thyorid issues as well. Read labels. Avoid msg and hi fructose corn syrup!