Potato chips are piling on the pounds, study finds (AP)

LOS ANGELES � Blame the potato chip. It's the biggest demon behind that pound-a-year weight creep that plagues many of us, a major diet study found. Bigger than soda, candy and ice cream.

And the reason is partly that old advertising cliche: You can't eat just one.

"They're very tasty and they have a very good texture. People generally don't take one or two chips. They have a whole bag," said obesity expert Dr. F. Xavier Pi-Sunyer of the St. Luke's-Roosevelt Hospital Center in New York.

What we eat and how much of it we consume has far more impact than exercise and most other habits do on long-term weight gain, according to the study by Harvard University scientists. It's the most comprehensive look yet at the effect of individual foods and lifestyle choices like sleep time and quitting smoking.

The results are in Thursday's New England Journal of Medicine.

Weight problems are epidemic. Two-thirds of American adults are overweight or obese. Childhood obesity has tripled in the past three decades. Pounds often are packed on gradually over decades, and many people struggle to limit weight gain without realizing what's causing it.

The new study finds food choices are key. The message: Eat more fruits, vegetables, whole grains and nuts. Cut back on potatoes, red meat, sweets and soda.

"There is no magic bullet for weight control," said one study leader, Dr. Frank Hu. "Diet and exercise are important for preventing weight gain, but diet clearly plays a bigger role."

Doctors analyzed changes in diet and lifestyle habits of 120,877 people from three long-running medical studies. All were health professionals and not obese at the start. Their weight was measured every four years for up to two decades, and they detailed their diet on questionnaires.

On average, participants gained nearly 17 pounds over the 20-year period.

For each four-year period, food choices contributed nearly 4 pounds. Exercise, for those who did it, cut less than 2 pounds.

Potato chips were the biggest dietary offender. Each daily serving containing 1 ounce (about 15 chips and 160 calories) led to a 1.69-pound uptick over four years. That's compared to sweets and desserts, which added 0.41 pound.

For starchy potatoes other than chips, the gain was 1.28 pounds. Within the spud group, french fries were worse for the waist than boiled, baked or mashed potatoes. That's because a serving of large fries contains between 500 to 600 calories compared with a serving of a large baked potato at 280 calories.

Soda added a pound over four years. Eating more fruits and vegetables and other unprocessed foods led to less weight gain, probably because they are fiber-rich and make people feel fuller.

For each four-year period, these factors had these effects on weight:

� An alcoholic drink a day, 0.41-pound increase.

� Watching an hour of TV a day, 0.31-pound increase.

� Recently quitting smoking, 5-pound increase.

People who slept more or less than six to eight hours a night gained more weight.

The study was funded by the National Institutes of Health and a foundation. Several researchers reported receiving fees from drug and nutrition companies.

"Humans naturally like fat and sweet," said Dr. David Heber, director of the UCLA Center for Human Nutrition, who had no role in the study. "That's why we always tell people to eat their fruits and vegetables."

Pi-Sunyer, who also wasn't involved in the research, said the study gives useful advice.

"It's hard to lose weight once you gain it," he said. "Anything that will give people a clue about what might prevent weight gain if they follow through with it is helpful."

The federal government earlier this year issued new dietary guidelines advising people to eat smarter. This month, it ditched the food pyramid � the longtime symbol of healthy eating � in favor of a dinner plate divided into four sections containing fruits, vegetables, protein and grains.

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Online:

New England Journal of Medicine: http://www.nejm.org

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Alicia Chang can be followed at: http://twitter.com/SciWriAlicia

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FDA concludes silicone breast implants mostly safe (AP)

WASHINGTON � Federal health officials say the latest data on silicone breast implants show they are relatively safe, despite frequent complications that lead about one in five women to have the implants removed within ten years.

A Food and Drug Administration report issued Wednesday is the agency's first safety assessment of the implants since regulators returned them to the market in 2006. That followed a 14-year ban when only saline-filled implants were widely available.

The FDA pulled silicone implants off the market in 1992, saying manufacturers had not provided medical data showing their safety and effectiveness. At the time, there were worries about a connection to a variety of diseases, including cancer and lupus.

But the agency returned the implants to the market five years ago after most studies failed to find a link between silicone breast implants and those diseases. Patients and plastic surgeons say the silicone-filled implants look and feel more real than saline versions.

The approval came with conditions, including a requirement that the companies complete studies on women who have received the implants.

The FDA's safety endorsement is primarily based on those studies, conducted by the two U.S. manufacturers of the products, Allergan Inc. and Johnson & Johnson's Mentor unit.

But industry critics point out that most of the studies are incomplete, and many women have already dropped out.

For example, only 58 percent of women enrolled in a 1,000-patient study of Mentor's implants are still accounted for after eight years. Two larger studies of 40,000 women, conducted by both Allergan and Mentor respectively, have each lost a significant number of patients after just two to three years.

Dr. Diana Zuckerman of the National Research Center for Women and Families said most medical journals would not publish the studies cited by FDA because of the missing data.

"Once a medical product is approved, the manufacturers have no incentive to do these required studies properly," Zuckerman said. "So, we end up with useless information, which is what has happened with the largest, most important studies of silicone gel breast implants."

The FDA commented that "both manufacturers have communicated to the FDA the difficulties in following women who have received silicone gel-filled breast implants." The agency said it is working with Allergan and Mentor to increase participation and follow-up.

The most common side effect remains scar tissue which hardens around the implant, warping the shape of the breast. Other problems include implant rupture, wrinkling, and lopsided appearance, according to the report.

"Despite frequent local complications and adverse outcomes, the benefits and risks of breast implants are sufficiently well understood for women to make informed decisions about their use," the agency concludes.

Based on the company data, FDA says 20 to 40 percent of patients who have implants for cosmetic reasons will need another operation to modify or remove them within eight to 10 years. For women with implants for breast reconstruction, the number is even higher, at 40 to 70 percent.

Breast augmentation remains the most popular cosmetic surgery in the U.S., with nearly 300,000 women receiving saline or silicone breast implants last year.

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Big city got you down? Stress study may show why (AP)

NEW YORK � This may come as no surprise to residents of New York City and other big urban centers: Living there can be bad for your mental health.

Now researchers have found a possible reason why. Imaging scans show that in city dwellers or people who grew up in urban areas, certain areas of the brain react more vigorously to stress. That may help explain how city life can boost the risks of schizophrenia and other mental disorders, researchers said.

Previous research has found that growing up in a big city raises the risk of schizophrenia. And there's some evidence that city dwellers are at heightened risk for mood and anxiety disorders, although the evidence is mixed.

In any case, the volunteers scanned in the new study were healthy, and experts said that while the city-rural differences in brain activity were intriguing, the results fall short of establishing a firm tie to mental illness.

The study, done in Germany and published in Thursday's issue of the journal Nature, focused on how the brain reacts to stress caused by other people.

To do that, investigators had volunteers lie in a brain scanner and solve math problems. The volunteers expected easy problems, but they were in fact hard enough that each volunteer ended up getting most of them wrong.

While in the scanner, volunteers heard a researcher criticize their poor performance, saying it was surprisingly bad and disappointing, and telling the volunteers they might not be skilled enough to participate.

An initial study with 32 volunteers found city-urban differences in two brain areas. One was the amygdala, which reacts to threats in one's environment, and the other was circuitry that regulates the amygdala. Researchers found that volunteers from cities of more than 100,000 showed more activation of the amygdala than participants from towns of more than 10,000, and those in turn showed more activation than people from rural areas.

To assess any effect of where the volunteers grew up, the researchers assigned each an "urbanicity" score based on how many years they'd spent by age 15 in a city, town or rural area. The higher the score, the more urban their childhood life was, and the more activity showed up in the amygdala-regulating circuitry during the experiment.

A slightly different stress-producing test produced similar results with a different group of 23 volunteers.

But when a third group of 37 adults did mental tasks without being criticized for poor performance, they showed no urban-rural differences. That shows the effect comes from the criticism rather than just doing the mental task, the researchers said.

The study can't reveal why city life would boost the brain responses, but it could be because of the stress from dealing with other people, said Dr. Andreas Meyer-Lindenberg, director of the Central Institute of Mental Health in Mannheim, Germany, and senior author of the report. Animal studies suggest that early exposure to stress can cause lasting effects, he said.

Jens Pruessner, a study co-author from the Douglas Mental Health University Institute in Montreal, said the study illustrates a new avenue for understanding the risk factors for developing mental illness.

An expert in emotion and the brain who wasn't involved with the study, Elizabeth Phelps of New York University, said it's premature to draw conclusions about what the results mean for mental illness.

"These results are interesting but preliminary," she said. "This will raise a lot of interest in this idea. Whether or not it pans out in future research, who knows, but I think it's worth investigating."

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Online:

Nature: http://www.nature.com/nature

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