Findings are filling out the story behind the fat

By Nathan Seppa

Web edition: December 13, 2012
Print edition: December 29, 2012; Vol.182 #13 (p. 28)

2012 SCIENCE NEWS TOP 25: 18

As obesity expands the world’s collective waistline, researchers keep finding new reasons why we are getting fatter, and more consequences of the added pounds.

In 2012, scientists found that hormones such as oxytocin and testosterone seem to help protect against gaining weight, or at least against a runaway appetite (SN Online: 6/26/12; SN: 7/28/12, p. 11). Other work offered counterintuitive results, finding that diet soda might not help much (SN: 7/14/12, p. 14), and that worries about junk food access in schools may be overrated (SN: 2/25/12, p. 9).

It’s a mishmash, but this much is clear: More than one-third of people in the United States are already obese, and another third are overweight. In one generation, obesity has gone from a medical and social issue to a public health disaster.

Obesity contributes to atherosclerosis, metabolic problems and other chronic diseases. “If you can tone all that down, you’ll probably be better off, and losing weight is a good way to do it,” says biochemist Russell Tracy of the University of Vermont.

Obesity comes from more than just overeating, and researchers tracking down the underpinnings of unhealthy behaviors often find their way to the nervous system. Such efforts are revealing that commonly consumed soybean and corn oils can confuse calorie-sensing networks in the body. The body taps components in some vegetable oils to make endocannabinoids, homegrown appetite stimulants similar to compounds in marijuana. What’s more, certain brain areas get hyperactive in overeaters, particularly areas associated with food-reward sensations (SN: 10/6/12, p. 24).

While these findings may help scientists unravel the complexities of appetite, other obesity contributors might be more straightforward. Exposure to secondhand smoke in adulthood is linked to diabetes and obesity (SN Online: 6/26/12), suggesting that smoking bans, which are running far ahead of junk food bans, may be the first legislative acts to fight the obesity epidemic.

Another exposure, to antibiotics in infancy, seems to contribute to excess weight by age 3 (SN Online: 8/22/12). Work in mice suggests this antibiotic effect might stem from altering the intestinal mix of beneficial bacteria.

Even your neighborhood can be risky. Children living in areas with ample green space and a nearby grocery store are roughly half as likely to be obese as kids growing up without such amenities, even after accounting for other differences. The new findings draw attention to what scientists call the “built environment” — a risk factor that is modifiable (SN: 6/2/12, p. 17).

There’s good news, too. People able to take off weight disrupt a dangerous triad of obesity, inflammation and possibly cancer. New data show that women losing just 5 percent of their body weight experience a drop in inflammatory proteins and cells (SN: 6/2/12, p. 16). “Anything you can do to decrease your inflammatory status is probably a good thing,” says Tracy. As is often the case in medicine today, obesity is at the top of that to-do list.

Return to 2012 Science News Top 25