Health & Science

Your brain on junk food

Junk food is literally addictive, producing changes in brain chemistry similar to those cocaine causes, says a new study. To explore how overeating affects the brain, scientists at the Scripps Research Institute in Florida monitored electrical activity in the brains of rats given unfettered access to cheesecake, frosting, bacon, and other fatty, high-calorie foods. Not surprisingly, the rats quickly became obese. They ate compulsively and continuously, even ignoring electric shocks applied to their feet in the presence of food. (The shocks deterred two control groups of rats from eating.) As the food-addicted rats ate, the high-fat, high-sugar, high-salt foods lit up the pleasure centers of their brains just as if they were taking drugs; over time, the rats had to eat more and more fat, sugar, and salt to feel rewarded. “They lose control,’’ study co-author Paul Kenny tells Discovery News. “This is the hallmark of addiction.’’ When the junk food was removed and health food was offered, Kenny says, the rats were so upset that “they basically starved themselves for two weeks.’’ The finding doesn’t surprise food experts like Dr. Gene-Jack Wang of Brookhaven National Laboratory, who points out that fast-food meals and heavily processed foods are stripped of fiber and nutrition and designed to trigger innate preferences for fat, sugar, and salt. “We make our food very similar to cocaine now,” he says.

Exercising to keep weight off

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Twenty minutes of moderate exercise a day is sufficient to produce cardiovascular benefits—but for women who want to keep the pounds off, it’s not nearly enough, says the Los Angeles Times. Harvard researchers followed 34,000 relatively healthy middle-aged and older women from 1992 to 2007, and found that only those who exercised an hour a day managed to keep from steadily gaining weight as they grew older. That’s three times more exercise than the 150 minutes a week that’s necessary to lower the risk of heart disease and other illnesses. “You can still do much for your health with a lower level of exercise,’’ says study author Dr. I-Min Lee. “But if you want to exercise for weight control, it’s 60 minutes a day.’’ By exercise, researchers don’t only mean time spent on a StairMaster; brisk walking, yoga, and other daily activities count, too. The researchers noted that there is an alternative to spending seven hours a week exercising, if your goal is to avoid weight gain: Steadily cut down on calories as you get older.

Altering morals with a magnet

Scientists identified an area of the brain responsible for moral reasoning—and managed to scramble its judgments using a magnet. Under normal conditions, we tend to make moral judgments about people based partly on their intentions: Did they make a mistake, or did they intend to hurt someone or cause damage? Previous research showed that this calculus unfolds in a brain region called the right temporoparietal junction, or RTPJ, just behind the right ear. To better understand how the RTPJ works, MIT researchers asked volunteers to weigh the morality of acts depicted in various stories. In one, a woman puts a spoon of white powder in her friend’s coffee, thinking it’s sugar. The powder turns out to be poison, and the friend dies. While subjects listened to these stories, scientists applied a painless magnetic pulse to the scalp above the RTPJ, scrambling the electronic signals of neurons there. With this moral center inoperative, subjects gave less emphasis to intent and judged morality mostly on whether actions caused harm. So they were more inclined to condemn the woman in the poisoning accident for killing her friend. “You think of morality as being a really high-level behavior,” researcher Liane Young tells BBC.com. “To be able to apply a magnetic field to a specific brain region and change people’s moral judgments is really astonishing.”

Our new cousin: ‘X-Woman’

Archaeologists have found a 40,000-year-old pinkie bone in Siberia that appears to belong to a heretofore-unknown, human-like creature. DNA extracted from the bone was distinct both from humans and from ancient Neanderthals, who both walked the Earth at that time. The new species, dubbed X-Woman, “is some new creature that has not been on our radar screens so far,” paleogeneticist Svante Pääbo tells the Los Angeles Times. The DNA analysis suggests that the hominid species migrated out of Africa at a different time than humans, and thus is a cousin to our species, not a direct ancestor. If further study proves X-Woman truly to be a separate species, it would add another dimension to an increasingly complex understanding of hominid evolution. In 2004, researchers discovered another previously unknown hominid species, Homo floresiensis—the 3-foot-tall “hobbits’’ who lived on the island of Flores in Indonesia as recently as 12,000 years ago. Several different kinds of hominids likely shared the planet at the same time, says British anthropologist Chris Stringer, and we’re likely to find more new species soon. “This is just the tip of the iceberg.”