Bingeing on foods high in fat and sugar content may make us feel guilty, yet it's a behavior many return to time and again.
Lately, researchers have come up with several explanations. They're not exclusive and they're hardly comprehensive. But they all make some sense.
First, there's sleep -- or, rather, lack of sleep.
Swedish researchers found that people who had been deprived of one night's sleep purchased more calories and grams of food from a mock supermarket the next day than they did after a full night's sleep. A study of 14 normal-weight men showed they had higher levels of the hunger hormone ghrelin after losing a night's sleep, although there was no relationship between individual levels of the hormone and food buying.
Overall, on short sleep, the men chose an average of 9 percent more calories and 18 percent more food by weight than when given a set shopping budget to buy from among 20 high-calorie and 20 low-calorie foods.
The study results were published earlier this month in the journal Obesity.
Another recent study looked at the phenomena of tailgating among losers.
Researchers with the international business school INSEAD tracked the Monday food consumption of people in more than two dozen cities over two NFL seasons. They found that those living in cities with a losing team ate about 16 percent more saturated fat and sugar compared with their usual Monday consumption, while people living in cities with winning teams consumed about 9 percent less.
The trends held even when non-football fans were included in the sample, and the effect was particularly noticeable if a game finished close.
Researchers Yann Cornil and Pierre Chandon speculate that when our team loses, our self-esteem suffers and we cope by eating more food that's bad for us. Winning, however, appears to boost our self-control.
Other studies seem to suggest that obesity may actually change our brains, so we eat more high-fat, high-sugar foods.
One 2012 study in rats found that a high-energy diet high in saturated fats had a negative impact on their ability to remember and learn -- and to suppress memories, such as fondness for still more high-fat foods.
Researchers at American University in Washington, D.C., focused on the hippocampus -- the region of the brain responsible for memory and learning. They found that obese rats eating high-fat food performed worse on tests of learning and memory than did rats that had eaten only low-fat chow. The researchers also noted that the barrier between brain blood vessels around the hippocampus was impaired among the rats that ate high-fat food.
They speculated in journal Physiology and Behavior that the high-fat diet actually causes more overeating as it fouls up the inhibitory system within the brain. The same sort of cycle likely plays out in people.
A 2011 study even suggested that some people develop an addiction for high-fat, high-sugar foods that stimulate the release of more dopamine and other pleasure chemicals within the brain.
Researchers at the Oregon Research Institute reported on MRI scans of brains of a group of obese girls and leaner girls as they anticipated -- and then actually drank -- a chocolate milkshake. In the obese girls, the brain regions related to reward and the senses lit up more strongly when they were expecting the treat than when they drank it.
The scientists say that indicates that people who find food more exciting are more likely to overeat and gain weight. Over time, the more people eat high-fat, high-sugar foods, the less the brain's reward regions are activated by actually eating them.
The study was published in Current Topics in Behavioral Science.
(Contact Scripps health and science writer Lee Bowman at BowmanL@shns.com. Distributed by Scripps Howard News Service, www.shns.com.)