As a culture we are moving away from natural foods that are low in calorie and high in nutrition to foods that are calorie dense but very low in nutrition. As a nation we are at the same time at record level of approximatley 68% obesity but yet we are starving ourselves to death.
The reason for this is the number of highly processed "convenience" foods. There are chemicals added to our foods that are now know to be highly addictive.
First on this list is Artificial Sweeteners. While many people think they are fooling their bodies with things such as aspartame(Nutrasweet) and others it is actually having a very detrimental affect. The reason is that artificial sweetners actually cause rapid insulin spikes. When insulin spikes it signals the body to lay down fat. Also, constantly spiking your insulin level can exhaust your bodies receptors and eventually lead to Insulin Resistence and Type 2 Diabetes. Insulin spikes actually cause your body to crave more carbs.
MSG is used as a food additive in many processed foods as a flavor enhancer. It excites the part of the brain that regulates the bodies fat programs. In one study reported by Science Daily(Auguest 13,2008) people who consumed MSG were nearly three times more likely to be obese than non consumers.
High Fructose Corn Syrup is now gaining a lot of attention not only because of it's highly addictive quality but it is now being found that the body can not even burn off HFCS. Some researchers say that because HFCS is so energy dense the body may not be able to burn it off and it may go straight to fat. Also, Sugar is like a drug in the brain. When you consume sugar and HFCS, endorphins are released in the brain that have a morphine like affect. Like any drug your body becomes habituated to these chemicals and requires more and more to satisfy it's craving.
Here is a video that explains how these chemical additives cause weight gain.
In this video called FoodMatters it explains how fertilizers,chemicals and over cooking our foods are depleting the nutrients in our foods.