Let me just saw WOW! This article on Science Daily is a real eye opener about processed foods.
The basics of the article is that junk food, or pleasurable food, is addictive, the way cocaine is, and leads to over-consumption of these foods, which causes obesity. Scientists at Scripps Research Institute have finished a three-year study on rats that prove this. They found that when the mice ate high calorie, high fat food whenever they wanted because they had easy access to it, the rats lost all control of their eating habits. When the scientists tried to put those rats back on a healthy diet, the rats would not eat the food. Even when the scientists tried shocking the rats when they over ate, they would continue eating.
What they found in the brain itself was similar to that of someone who is addicted to cocaine. The main receptor responsible for addiction to drugs is called the dopamine D2 receptor. The amount of these receptors is reduced when a person is addicted to something, like in the case of cocaine. These receptors get turned off because they are overstimulated by a rush of dopamine, the pleasure hormone/neurotransmitter. That is how the body adjusts to the over-stimulation.
So now you have proof that junk food is addictive, that includes all the food products that have sugar and high fructose corn syrup. No wonder people have such a hard time changing their life style.