Let's face it, our country is fat. The concept of normal weight seems to be an idea of the past in America. In 2010, there were 9 states with an obesity rate falling over 30% and about 10% of all medical expenses in the US are spent to combat obesity. Overweight people are everywhere, and the fight against fat seems to be failing despite the effort of diet books, weight loss programs, and supplements. Are we doomed in this battle against the obesity epidemic? We are if our brains have any say in the matter. Overtime, our brains have evolved to promote hunger and fat storage in the body. Before the times of fast food restaurants on every corner, humans had to hunt for food and there was great uncertainty surrounding the time and size of the next meal. From this, our brain learned to resist weight loss in preparation for long periods of time without food.
There are many different factors, both structures and molecules, working together in the brain that encourage eating. Recently, scientists have discovered fat cells release a hormone known as leptin that travels to the hypothalamus (a brain structure involved in the regulation of hunger, thirst, and sleep) and signals to reduce the sense of hunger so we stop eating. If this hormone has been identified in reducing hunger, why not pump as much as we can into the obese population and watch the pounds shed? Although this theory seems plausible, trials have shown no significant weight loss in humans injected with the hormone. To understand why, we have to remember where the hormone begins its journey to the hypothalamus: fat cells. A person is deemed "obese" when they have a high percentage of fat cells in their body. Level of leptin is directly proportional to the amount of fat in someone's body; therefore, obese people already have a great deal of fat cells actively releasing leptin. The use of synthetic leptin injections has proved to be useful in maintaining weight loss but it does not work to help a person lose the original weight. Hope in hormones is not completely lost as a source of weight loss though.
Researchers in Japan identified another hormone named ghrelin that is also involved in hunger. Ghrelin is actively released from the gut before a meal and levels of this hormone fall immediately after eating. Scientists in Washington took this information and began to study the levels of ghrelin in people who have lost weight due to dieting compared to those who experienced weight loss by means of gastric bypass surgery. They found that those who lost weight with diet had increased levels of ghrelin while those who underwent surgery saw ghrelin levels decrease significantly. The bodies of the dieting weight losers still have cells that release ghrelin and they seem to be trying to tell the brain to gain back what it has lost. Locating and removing specific regions of the gut that release this hormone could be highly effective in helping people lose weight and keep it off in the future.
We are a ways away from knowing exactly which hormones in which combinations will help millions lose weight, but something as simple as altering sleep patterns could be a solution. According to the article, research done at Harvard University found that when healthy volunteers were subjected to disruption in their usual sleep-wake cycle, they developed prediabetic blood sugar levels; giving evidence that circadian cycle has metabolic effects. The American lifestyle involves staying up late and being active for long days which could be contributing to increased instances of metabolic disease. "But I have a set sleep cycle and I am still constantly struggling to lose weight." Well maybe you just love food too much. No, seriously. A study done by the Oregon Research Institute found that overweight participants showed higher levels of activity in regions of the brain that encode the sensory experience of food on an fMRI while consuming a chocolate milkshake. So obese people get more pleasure from food? Sort of. Similar to a drug addict who needs more drugs to experience the same high they once got, the brain needs more and more food to experience that original pleasure from food.
As our country continues to expand its waist line, we will continue to search for a way to lose weight despite the efforts of our brain. Multiple drug combination therapies are being studied by pharmaceutical companies every day and universities are attempting to rewire parts of the brain involved in triggers of hunger. One thing is for sure: there is no magical diet or weight loss program that will cure obesity. Instead, maybe that magic we are searching for exists in neuroscience.
From the article "The Hungry Brain" by Dan Hurley, Discover Magazine, June 2011