Mice that easily became addicted to a chocolate bar diet may shed fresh light on why we binge eat.
Their mission isn't made any easier by the fact that many developed countries — such as the United States — will often provide a perfect context for damaging habits such as binge eating.
Such contexts — referred to by researchers as "obesogenic environments" — are defined as "the sum of influences that the surroundings, opportunities, or conditions of life have on promoting obesity in individuals or populations."
To better understand how obesogenic environments can lead to binge eating and promote obesity, Mara Dierssen, from the Centre for Genomic Regulation, and Rafael Maldonado, from the Pompeu Fabra University — both in Barcelona, Spain — decided to simulate such an environment in the laboratory, working with mice.
Their results have been published as two complementary articles in the journal Addiction Biology.
How environments lead to addiction
Dierssen and Maldonado, together with colleagues from both institutions, created an obesogenic environment for the rodents by offering them different feeding options.
The animals were given the regular chow that they would normally eat for a balanced diet, as well as a medley of chocolate pieces obtained by chopping up a range of commercially available chocolate bars. They were also given the option of a high-fat, "cafeteria-style" feed.
Interestingly, once they were offered a plentiful but unhealthful feeding alternative, it didn't take long for the mice to start binge eating, displaying addictive behaviors, and gaining excessive weight.
In one telling instance, the researchers gave the animals access to the chocolate for only 1 hour per day, which resulted in the mice compulsively gorging themselves with the sweet mix.
In short, they ended up consuming as much chocolate in just 1 hour as they would otherwise have eaten over an entire day, had it been regularly on offer.
Like people displaying signs of addiction, the mice would much rather wait for the chocolate to be given to them than eat the regular chow that was constantly available to them.
But the chocolate, which did not offer the mice the nutrients that they needed, did not effectively decrease their sense of hunger. Moreover, the mice that ate either chocolate or a high-fat diet showed a distinct change in their daily feeding routine.
Despite the fact that mice normally prefer to eat at night, these rodents started to eat preferentially during the daytime. They also chose frequent, "snack-like," feeding patterns, rather than regular, but more infrequent, and more plentiful meals.
'Trapped' in a vicious cycle
Researchers have noted that overweight people who attempt to shed excess kilograms by dieting and following more healthful eating habits will often relapse after participating in weight loss programs or initiatives.
This pattern is a main obstacle when it comes to maintaining healthful eating behaviors. Following the results of their experiments, Dierssen and Maldonado suggest that the reason behind these relapses may be that obesogenic environments impair the control that people have over their eating habits.
Therefore, they may fall into a vicious cycle where one unhealthful choice leads to the next, and so on.
"Our results," explains Maldonado, "revealed that long-term exposure to hypercaloric diets impair the ability to control eating behavior leading to negative effects on the cognitive processes responsible for a rational control of food intake."
Dierssen also notes that certain metabolic diseases are not just a result of biological factors; they may be also be caused by uncontrolled behaviors, and this is where health professionals should learn to intervene.
"Obesity is not just a metabolic disease — it is a behavioral issue," she says, adding, "People who are overweight or obese are usually told to eat less and move more, but this is too simplistic."
"We need to look at the whole process. By understanding the behaviors that lead to obesity and spotting the tell-tale signs early, we could find therapies or treatments that stop people from becoming overweight in the first place."
As their next step, Dierssen and Maldonado would like to conduct further research into addictive behaviors both in the case of animals and humans who tend to overeat.
"It is very hard to lose weight successfully, and many people end up trapped in a cycle of yo-yo dieting," stresses Dierssen.
"These studies reveal the major behavioral and cognitive changes promoted by hypercaloric food intake, which could be crucial for the repeated weight gain and the difficulties to an appropriate diet control," concludes Maldonado.