Aug 02 2011
The obesity debate rages on. I have covered this topic quite a bit on this blog – what factors contribute to overweight and obesity and what strategies are effective in maintaining a desired weight?
The outlook is fairly grim from the perspective that there are no easy answers or guaranteed techniques (from an intention to treat analysis). About 95% of all people who try to lose weight fail long term. Various diet revolutions (low fat, low carb, and an endless sequence of fad diets) have failed to produce results. Meanwhile, overweight and obesity in the industrialized world continues to rise.
Now a group of neuroscientists (Bradley M. Appelhans PhD, Matthew C. Whited PhD, Kristin L. Schneider PhD and Sherry L. Pagoto PhD) have weighed in on the debate in an article titled: Time to Abandon the Notion of Personal Choice in Dietary Counseling for Obesity? Not surprisingly, they take a neuroscientific perspective on weight control.
The essence of their article is that the “personal choice” paradigm of weight control has essentially failed (sound familiar?). It is simply too difficult to control eating with pure force of will. You can do it for a while, but not consistently enough long term. It takes just a moment of weakness to undo an entire day of self-control.
They argue that by understanding eating as a behavioral result of neurological processes, maybe we can come up with some strategies that will work.
They identify three primary neurological processes at work: food reward, inhibitory control, and time discounting. Food reward is probably obvious – the reward centers in our brains give us a happy dose of dopamine when we give in to our food cravings. We evolved in a calorie restricted environment and we crave calorie dense food – sugar and fat. They write:
Obesity has been viewed almost exclusively as a disorder of energy homeostasis in which overeating results from insufficient satiety signaling or amplified hunger signaling. However, research conducted over the past decade has demonstrated that the sensory experience of palatable food can easily override homeostatic controls of energy balance, leading to overeating in the absence of true physiological hunger.
In other words, we eat even when we don’t need the calories because food is just so yummy. Neurological speaking, the need for calories drives hunger, but in addition we evolved a pleasure reward response to the act of eating, and this alone can drive overeating. In this sense eating can be like any other reward-driven addictive behavior.
The next factor, inhibitory control, is our ability to override our food cravings. They describe, essentially, the neurological basis of “will power.” The authors write:
Dieters who consistently selected health over taste showed greater dorsolateral PFC (prefrontal cortex) activation when choosing the healthier options compared to those who more often selected taste over health. Further, there was evidence of functional connectivity between the dorsolateral PFC and brain areas associated with reward processing, consistent with the notion that the dorsolateral PFC inhibits the influence of reward on behavior.
Therefore we can look at our food choice as a struggle between the reward centers of our brain and the prefrontal cortex trying to exhibit control. The authors do not get into this – but other research shows that our ability to maintain self-control is reduced in many situations. For example, when we have already expended energy in other areas of self-control, we “reward ourselves” with a little overeating. Also, when we are sleepy or even physically exhausted, our inhibitory control is reduced.
So again, a long day of healthful eating can be undone by a moment of weakness when we are stressed, tired, or expended from others acts of self-restraint. Watching other people indulge will also lower our resistance through social pressures.
Finally the authors discuss time discounting:
A third factor that likely contributes to the low success rates of dietary interventions for obesity is the human tendency to devalue delayed rewards. Most of us would prefer to receive $200 today rather than $300 a year from now. This decision illustrates the fact that the brain discounts the value of money and other rewards over time, resulting in impulsive, short-sighted decision-making.
I would add to this another factor – denial and rationalization – which ties in to the other factors above. We want to eat the yummy cheesecake. But our resistance is finite, and may be compromised by many factors. Besides, we can deal with the consequences later – but the cake will taste really good right now. So we deny the known consequences of eating the cheesecake and rationalize our decision. We haven’t eaten that much today. We can afford a little cheesecake. We’ll just do some extra exercise tomorrow.
While I found the article very interesting, it isn’t really discussing anything new. The authors primarily discuss the neurological basis of what psychologists have already copiously documented.
I do like the approach, however, of looking at eating as a consequence of neurobehavioral factors. (This may be, however, because I tend to rely on intellectualization as a defense mechanism, and looking at behavior as brain activity is a great way to intellectualize our actions.)
The recommendations that the authors derive from this approach is to reduce the tempting foods in our environment. So, do not rely on continuous self-control, just don’t have a lot of calorie-dense food around the house. Also, limit buffets and other open-ended eating opportunities. They also advise stress management, as stress further drive overeating.
Again – this is all nothing new. But it is good to emphasize that trying to manipulate the food environment is likely to be more successful than navigating an environment that strongly encourages overeating with will power alone.
We also might extend this beyond the personal environment discussed by the authors to the social environment. This gets to the issue I recently discussed on Science-Based Medicine – to what extent should we use regulation to change the food landscape to counter the obesity epidemic.
I do think that this is where the conversation needs to be – not which magic combination of foods or nutrients will cause the weight to melt away without effort.
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