We are accustomed to eating when we are hungry and then not eating when we are full, so it is easy to think that people pack on pounds because of some sort of moral failing. But in reality, being overweight extends well beyond any moral culpability. Appetite is the product of complex unconscious forces cobbled together by evolutionary necessity. Fortunately, it is also possible to control your appetite and thus your weight if you understand the physiological forces at work.
Features
Appetite can be defined as the desire to eat food, which is expressed as hunger. It usually occurs when blood glucose levels become low--glucose is the molecule transported to the cells for energy. Ghrelin is the hormone that stimulates hunger, but leptin is just as important. According to Scientific American, leptin is a hormone that is secreted by fat tissue to suppress appetite. If blood glucose levels increase, then insulin is released to remove extra insulin from the blood, which means that the body must then release leptin to tamp down on the desire for food.
Studies
A 2009 study published in the The Journal of Clinical Investigation found that a diet high in saturated fat actually caused a leptin and insulin resistance in the brain after three days. Another study published in the American Journal of Physiology found that the sugar fructose, a key ingredient in high fructose corn syrup, also causes a leptin resistance. These studies were done on mice and rats, but they might indicate a similar response in humans.
Expert Insight
William Banks of the Saint Louis Veterans Affairs Medical Center states that high levels of saturated fat in the bloodstream block leptin's passage into the brain, causing us to eat more than we usually would. Once our metabolism spins out of control, it can exacerbate weight gain and metabolic problems.
Causes
It is not well understood why some compounds that we typically consume may flout our normal regulatory mechanisms, but it is also true that our brain chemistry can have trouble dealing with the environments we find ourselves in. Humans evolved in a world where we had to hunt to eat foods that we can now buy in a supermarket. The agricultural revolution also changed our palate by making rare foods common.
Recommendations
In order to control your appetite, take a few precautions. Saturated fats should be limited to no more than 10 percent of your diet--the American Heart Association recommends 7 percent at most. You should also control spikes in blood sugar. Eat more fiber, which slows the absorption of glucose into the blood, and avoid carbohydrates with a large effect on blood sugar, which will simply cause insulin to clear the glucose from the blood faster and leave you just as hungry as you were before. But neither should your blood sugar levels drop too low, causing extreme hunger and overeating. Keep yourself well-fed throughout the day.
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