“Seduced by Food: Obesity and the Human Brain” is the irresistible title of a piece by Stephen Guyenet, Ph.D. (who is an obesity researcher at the University of Washington) which touches upon many of the topics discussed by Childhood Obesity News. For starters, he acknowledges the reality of food addiction, though perhaps not perceiving it as being so widespread and pervasive as it is in Dr. Pretlow’s view.
But let Dr. Guyenet speak for himself:
Addiction is what happens when the reward system is over-stimulated by drugs, sex, food or other high-reward stimuli. In susceptible people (about 3 percent of the US population), highly palatable/rewarding foods are quite literally addictive, leading to binge eating behavior. For the rest of us, these foods may not literally be addictive, but they do often drive us to eat them more than we think we should, despite negative consequences to our weight and health.
Hmmmm. When the use of a substance continues, despite adverse and even disastrous consequences, that actually is one of the addiction criteria outlined by the Diagnostic and Statistical Manual.
In the body’s energy homeostasis system, everything is so amazingly intertwined, it’s not easy to choose a starting point, but let’s start with leptin. Along with other hormones, leptin works to keep things in balance. Made by fat tissue, it informs the hypothalamus about how to regulate fat storage. When food intake is restricted, the mass of fat shrinks, and less leptin is produced. So the hypothalamus gets busy motivating the body to seek food, and, meanwhile, reminds it to use its stored calories more wisely.
When food is over-consumed, there is more fat mass, more leptin, and the appetite decreases, and so does food-seeking behavior, and the body freely uses up the extra calories. It’s an elegant system, in the best-case scenario. But sometimes it goes bad, and obesity experts are interested in discovering why.
Guyenet explains the dilemma:
Some researchers believe the energy homeostasis system defends against fat loss more effectively than fat gain. However, most obese people regulate their body fat just fine, but their brains ‘defend’ it at a higher level than a lean person… If we want to understand how to prevent and treat obesity, first we have to understand why obese people defend a higher level of fat mass than lean people.
Apparently a simple diet, “low in palatability and reward value,” is capable of creating a reduced sensation of hunger. More importantly, a simple diet can persuade the body out of its willingness to “defend” the amount of fat clinging to it. Here, Guyenet finds the explanation for a seeming paradox:
This may be a reason why virtually any diet in which food choices are restricted (e.g., Paleo, vegan, fruitarian), including diametrically opposed approaches like low-fat and low-carbohydrate diets, can reduce food intake and body fatness in clinical trials.
For background, he recalls the experiments in which rodents preferred junk food and electric shocks over the bland pellets and no shocks. Of course someone also had to do junk-food science with humans, proving the obvious. Even though we know it makes us fat, humans love junk food.
(To be continued…)
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