The dietary buzz word in the 1980's was low fat. In order to pander to the public's desire to eat less fat a new generation of low fat treats, foods and snack foods were developed. A perfect example are the SnackWells. All of these low fat foods had two things in common. They had less fat, but they had more empty calories from carbohydrates.Think of carbohydrates as sugar because your metabolism rapidly converts starches to sugar.
As Americans ate more low fat foods and more empty calories they gradually became fatter and fatter. The result is the obesity epidemic that is now the number one public health problem. The reason for the weight gain is easy to explain. It has to do with blood chemistry. Remember carbohydrates are sugar. A bagel is no different than candy bar after it is digested. Sugar stimulates the body to produce insulin. Insulin drives the fat cells into storage overdrive. This causes weight gain.
As people continue to overdose on low fat high carbohydrate foods their cells become more resistant to insulin. This causes them to gain even more weight and also increases their insulin resistance. The result in many instances is Type 2 diabetes.
The lessons to be learned is that fat in your diet is not necessarily bad. Refined carbohydrates in your diet are always bad. Eating a reasonable diet with a balance between protein, fats and whole grains is always good.
You are what you eat. A good rule to follow before taking a bite is to ask yourself whether this particular food will nourish me or it it just empty calories.