Losing weight comes with a lot of health benefits—including making your brain sharper.

Yes it turns out that overweight may damage cognitive functions (认知功能) such as memory and attention. There have been few studies of overweight and cognitive functioning, possibly because it is generally believed that it is not a primary risk cause for poor cognitive performance. Losing weight, therefore, may help improve these mental functions, according to a new research led by John Gunstad, assistant professor of psychology at Kent State University.

Growing evidence suggests that being fat is linked to cognitive deficits (缺陷). So Gunstad and his team guessed that losing weight might improve mental function. For their study, they measured memory and attention in a group of 150 overweight participants, some of whom had some kind of operation for weight loss and some did not. All of the volunteers completed mental skills tests to assess their abilities of memory and attention at the beginning of the study, and again 12 weeks later. To begin with, about 24% of the patients showed damaged learning and 23% showed signs of poor memory when tested. At the end of the study, those who had lost weight after operation improved their scores into the average or above average range for cognitive functions. Scores for the volunteers who didn't lose weight dropped even further.

The study helped Gunstad to find out whether losing weight had any effect on mental function. Now that he's seen the positive effect that weight loss can have on memory and attention, he says he will next study those who choose to lose weight by the traditional way—eating healthier and getting more active. He expects that losing weight in this way will have a similarly positive effect on the brain. "If we can improve the condition with operations, then we can probably produce the same change with behavioral weight loss as well," he says.

The federal school lunch program for 30 million low-income children was created more than half a century ago to combat malnutrition(营养不良). A breakfast program was added during the 1960s, and both attempted to improve the nutritional value of food served at school.

More must be done to fight the childhood obesity epidemic(流行的), which has caused a frightening peak in weight-related disorders like diabetes, high-blood pressure and heart disease among young people. The place to start is schools, where junk food sold outside the federal meals program—through snack bars and vending machines—has pretty much canceled out the benefits of all those efforts.

Federal rules that govern the sales of these harmful foods at school are limited and have not been updated for nearly 40 years. Until new regulations are written, children who are served healthy meals in the school cafeteria will continue to buy candy drinks and high sodium(钠) snacks elsewhere in school.

Many states' school districts have taken positive steps, but others are likely to resist, especially districts that sell junk food to finance athletic program extracurricular activities, and even copier expenses.

Those districts should take note of a study released in 2009 in West Virginia showing that the budgetary costs of switching from sodas to healthy drinks such as fruit juice, milk, and water were very little. Even if the switch costs money, so be it. The school should not be trading their students' health to buy office supplies.

Over the last 50 years, the obesity rates for adolescents have tripled. Unless there is decisive action, weight and inactivity-related disorders will bother a steady larger proportion of the work force and replace smoking as the leading cause of premature death.

Foreseeing a time when a patient's own cells may be harvested, multiplied, and fashioned into a replacement organ, researchers in Boston have successfully transplanted laboratory grown bladders (肾) into six dogs.

For a century, physicians have replaced diseased or damaged bladders by removing sections of a person's intestines (肠子) and shaping them into a substitute bladder. While the procedure offers some relief to patients, complications often develop because nature designs intestinal tissue for a purpose-absorbing nutrients-other than holding waste liquid of the body. "You start absorbing stuff that should be removed," says Anthony Atala of the Children's Hospital in Boston.

Other physicians have turned to human-made materials to create artificial bladders, but those efforts have also run into problems. Consequently, to build a better bladder, Atala and his colleagues decided to employ the organ's own cells.

To turn the cells into an organ, the researchers first form plastic which can break down naturally into bladder-shaped shell. They then coat its outside and inside with layers of cells needed.

To test this strategy, Atala's group obtained bladder tissue from dogs and grew it into organs. After removing the dogs' bladders, the investigators implanted (移植) the artificial ones coming from the dogs' own cells. Within a month, the organs began to perform like normal bladders.

Within three months, the plastic shells had broken down naturally, and the implanted organs were hard to distinguish from natural ones. Blood vessels (血管) quickly grew into them. Moreover, nerves seem to form proper connections with the new organs, allowing the dogs to regain normal control of their bladders. Some dogs have had the artificial bladders for nearly a year without any problems.

While the bladders of dogs closely resemble those of people, Atala warns that more testing of this transplant strategy must occur before artificial bladders are ready for the clinic.