-- A low fat diet could actually contribute to weight gain, since certain fats are required to help in digest and metabolize foods.
-- Certain substances are fed to livestock and poltry to increase the weight of the animal. We eat the meat of those animals and it only stands to reason that these substances are passsed on to us, causing weight gain.
Some years ago it was found that the hormones fed to cows to increase production actually was passed on to children that drank the milk form those cows causing growth anoramilties in cetain children.
Some boys had premature hair growth on their faces, girls would have periods earlier than normal and some other things that I can't remember off hand.
Does it not stand to reason then, that certain types of substances or hormones could actually cause weight gain?
-- The much more stressful lifestyle that Americans lead could also be a factor in causing weight gain since we tend to eat faster which in turn causes our food to turn to fat since it is poorly digested.
-- Finally and probably most importantly, the American style of eating includes large portions of highly processed foods with little fibers and little nutrients, not to mention hybrid foods and foods that are loaded with chemicals which we have no idea what effect they have on our bodies.
-- And with the extremely computerized lifestyle more and more Americans are leading, sedentary living seems to be more the case. Lack of exercise is a very high contributer to obesity, along with heart disease and other malidies that overweight is connected with.