Body & Brain

Obesity expanding
The obesity rate worldwide has roughly doubled in the past three decades, hitting 9.8 percent for men and 13.8 percent for women in 2008, an international team of researchers reports online February 3 in the Lancet. Pacific Island nations collectively recorded the highest average weight. Among high-income countries, the United States ranked heaviest, followed by New Zealand. Japan and Singapore weigh the least. Bangladesh women weighed least among their gender, as did men in the Democratic Republic of the Congo. Among European females, Swiss women were the thinnest. —Nathan Seppa

HPV shots for men
The vaccine against human papillomavirus, now available and recommended for girls to prevent cervical cancer, fights the virus in adolescent boys and young men, too, researchers report in the Feb. 3 New England Journal of Medicine. More than 4,000 boys and men ages 16 to 26 were randomly assigned to get either three vaccination shots or three placebo injections over six months. Thirty months after the start of the trial, vaccinated volunteers had 36 genital lesions caused by HPV while the unvaccinated group had 89, an international team reports. The virus can cause penile, anal and throat cancer in males.  —Nathan Seppa

Dogs spot cancer
A Labrador retriever trained to spot colorectal cancer by sniffing breath or stool samples was able to replicate the feat with better than 90 percent accuracy when confronted with samples from healthy people and people with the cancer, researchers at Kyushu University in Japan report online January 31 in the journal Gut. The scientists note that while using dogs for diagnostic purposes might be impractical, the study establishes that a specific cancer scent exists and suggests that cancer-specific compounds in circulation might be identified someday and used for early detection of cancer. —Nathan Seppa

Sleepy tots Experts often fret about how children don’t sleep as much as they used to. Yet a close review of the scientific literature suggests that this truism may not be so true. Australian scientists scrutinized 51 sleep-related studies that make a claim about kids’ sleep levels and found that a majority of the reports repeat this “fact” without a shred of evidence. They deemed evidence provided by the rest of the studies ambiguous. In a paper to appear in an upcoming issue of Sleep , the researchers don’t come down on one side or the other, but they do caution that the claim has a “limited scientific basis.” — Laura Sanders

Fat-burning fat
Energy-burning brown fat helps clear triglycerides out of the blood in mice, a team led by researchers from the University Medical Center Hamburg-Eppendorf in Germany has shown. Triglycerides are the chemical form most fats take in food and in the body; high levels in the blood can clog arteries. Brown fat was recently discovered in adult humans and many researchers hope that boosting brown fat’s activity can reverse obesity. In the new study, published online January 23 in Nature Medicine, brown fat burned triglycerides for fuel when mice were kept in the cold. —Tina Hesman Saey

HIV increases stroke risk
Having an HIV infection seems to triple a person’s likelihood of having a stroke, for reasons that remain unclear. The added risk might result from the cocktail of drugs HIV patients often take to keep their disease at bay, or might simply reflect the fact that HIV-positive people are living longer now than they had in the past, and stroke is a disease of older people, the researchers note. A team led by scientists at the University of California, San Diego reviewed all stroke hospitalizations in the U.S. over a decade in preparing the report, which appeared online Jan. 19 in Neurology. —Nathan Seppa