Weight Loss Success Takes More than Willpower

  • by Staff Writer, MedPage Today

Obese patients who are trying to lose weight need to understand that they're up against a complex interaction between neurobehavioral processes and a saturated food environment, dietitians said.

Science is increasingly showing that this interaction is largely responsible for weight gain, according to Bradley Appelhans, PhD, of Rush University Medical Center in Chicago, and colleagues in the Journal of the American Dietetic Association.

Emphasizing this dietary dynamic may be more effective than simply instructing patients to eat less calorie-dense foods, they wrote.

Current approaches to dietary counseling for obesity are rooted in personal choice, Appelhans and colleagues explained. Patients typically receive education about how dietary choices impact energy balance and are told to adjust their eating patterns.

When they fail, physicians often attribute it to lack of willpower, even though body mass is 55% to 75% heritable, the researchers said.

Thus, shifting the emphasis away from poor personal choices to brain systems interacting with a 'toxic' food environment may improve outcomes while reducing stigma, Appelhans and colleagues said, and a growing body of scientific evidence supports the idea.

Specifically, there are three neurobehavioral processes at work in obesity: food reward, inhibitory control, and time discounting.

In food reward, the same neural processes that are active in sex, gambling, and substance abuse are at work, the scientists said. Processing occurs in the mesolimbic system, invoking both motivation and pleasure.

Pleasure from eating food is tied to opioid neurotransmission in nucleus accumbens, while the motivational aspect is mediated by dopamine pathways.

Motivation may play more of a role in obesity than pleasure, the researchers explained, because heavy patients report that they do not derive more pleasure from tasty food than normal-weight patients.

Overall, blunted mesolimbic signaling may represent a deficiency in neural reward processing for which patients compensate by consuming too much palatable food, they said.

Another crucial aspect to obesity is inhibitory control, or the power to ignore cravings that result from food reward. This has long been considered a patient's central task in weight management, but scientific evidence has emerged that indicates have neurobiologically challenging this task can be.

Inhibitory control is mediated by the prefrontal cortex, particularly the dorsolateral prefrontal cortex, which has been shown to inhibit the influence of reward on behavior.

"Inhibiting our food intake is not simply a matter of reducing the motivation to eat; it involves actively controlling behavior despite a strong motivation to eat," the researchers wrote.

Finally, time discounting -- the human tendency to devalue delayed rewards -- explains why patients make choices that aren't in their best long-term interest.

The process is governed by the same brain regions associated with food reward and inhibitory control, Appelhans and colleagues said, and weight loss is directly at odds with it. For instance, it is challenging to forgo more palatable food now, for better health in the future, they said.

The growing scientific literature has implications for counseling, Appelhans and colleagues added, with two important messages that physicians and dietitians should pass on to patients:

  • Explain that obesity is heavily influenced by genetic and environmental factors.
  • Emphasize that weight loss can be achieved by minimizing the impact of the environment on behavior.

The first message acknowledges that patients are working against the odds of genetic vulnerability and a powerful food environment, which normalizes their frustration; the second returns some control to patients.

Strategies to improve patient environment include removing bad foods from the home and workplace, minimizing stress (which can make the mesolimbic system go haywire), and preparing healthy foods in advance so they're ready when hunger kicks in.

To overcome time discounting, patients can take small steps that focus on short-term weight loss goals, the researchers said.

"Enough progress has been made to enable dietetics practitioners to shift from a model of obesity counseling grounded in personal choice to one rooted in brain processes that govern eating behavior in an obesity-promoting environment," the researchers wrote.

"Even if this approach is no more effective in producing weight loss than current practices, it is much less likely to elicit patient stigmatization," they concluded.


Appelhans reported consulting for Merck.