High preservatives / Airplane food Dilemma

A few years ago I started a greta job as a flight attendant for a charter. Since then I have gained a bunch of weight and was recently told that the preservatives in the food could be the cause. I have noticed that other flight attendants that don't eat the air meals, are in better shape. Is this due to a rejection of the crew meals or simply indicative of a more strict mealplan overall?
Thanks, Jolie