This article is also authored by Cathy Woodard and Camille Kimball
America has a serious weight problem, with more than 60 percent of adults classified as overweight or obese. Starting at age 30, most people gain about a pound per year despite efforts to keep it off. We are bombarded with countless books, articles and infomercials touting the latest fad diet. Despite all of this advice, the average overweight adult finds losing weight a difficult and unpleasant task and nothing has succeeded in making us thinner. Americans are actually eating healthier foods, but they are consuming more calories. The sheer amount of food we eat is a large part of the problem.
Why is it so difficult to lose weight?
We may live in the 21st century, but we have prehistoric genes that helped our ancestors survive countless feast-then-famine cycles. Over thousands of years of human development, genes that prevent weight loss became more advantageous than genes that prevent weight gain. Scientists call this the “thrifty gene hypothesis.” Early man benefited from genes that stored fat when food was plentiful and slowed metabolism when food was scarce. Our early ancestors also expended a large amount of energy hunting and gathering for the food they ate. Nowadays, “hunting and gathering” often means selecting an entree from the freezer and popping it in the microwave. Modern man is consuming more calories than he is expending, and our ancient genes, unaware that no famine will follow, turn this excess into fat.
What role do hormones play?
Hormones play an important role in how and when we eat. Mechanisms that prevent weight loss include signals telling you to eat when hungry, and signals telling your body to decrease its metabolism when food is scarce, such as when you diet. The hormones, leptin (an important hormone released from fat), ghrelin (a stomach hormone), NPY and αMSH, among others, signal the body that the person is hungry and should initiate eating. Other factors that may act to regulate metabolism include thyroid hormone, catecholamines and uncoupling proteins.