Using ultrasound to peer at the arteries of 471 youngsters aged 13 to 15, researchers at St. George's Hospital Medical Center in London found that extra fat lessened "distensibility," a measure of arteries' ability to expand, according to a report in the Sept. 20 online issue of Circulation.
"This is more evidence that being overweight as an adolescent does have long-term implications," said study author Peter H. Whincup, a professor of cardiovascular epidemiology at St. George's.
It's been known that severe obesity in teenagers damages the endothelium, the delicate lining of the arteries, reducing their ability to expand. This study shows that the damage can occur at "body-mass index levels well below those considered to represent obesity," the researchers wrote.
Traditionally, Whincup said, the major concerns about heart disease have been blood pressure, cholesterol and "above all, smoking."
"What we are looking at here is an early model of risk, the balance of determinants in the early years of life," he said. "Obesity, or degrees of it, are the dominant factors at this stage."
Until recently, heart disease risk factors such as high cholesterol and high blood pressure were uncommon in childhood, the researchers noted. One reason for the study was that such risk factors have become increasingly common as the rate of childhood obesity has soared.
Some of the children in the study had been studied earlier, when they were 9 to 11 years old, so the researchers could look at the effects of various heart disease risk factors over time.
They found that insulin resistance, diastolic blood pressure (the second number in a blood pressure reading) and levels of C-reactive protein, a marker of inflammation, were also associated with reduced distensibility. The association with blood pressure showed up as early as age 9, the researchers said.
"The message is not for individuals at this stage," Whincup said. Instead, he said, it is for society at large to take more steps to keep children and adolescents slimmer.
"There is no magic formula," he said. "It is simply that calorie intake is too high in relation to expenditures of energy."
A combination of better diet and more exercise -- standard recommendations for adults -- apply to adolescents as well, he said.
"This whole concept of distensibility is potentially an important one because one of the difficulties in understanding the early process of atherosclerosis is how to look at it," said Dr. Stephen Daniels, a professor of pediatrics at the Cincinnati Children's Hospital Center, and a spokesman for the American Heart Association. "This is one way to do it."
The real-life lesson of the study is that overweight "is having an adverse effect at many levels," he said. "In a world where more and more children are getting into obesity, this says that we have to be more aggressive in trying to prevent it."
More information
Find out more about childhood obesity and tips on curbing it at the American Academy of Child and Adolescent Psychiatry.
That's true even if the family's goals of eating together each day falls short occasionally, according to a study published in a recent issue of the journal Obesity Research.
Eating together as a family has long been recommended by nutrition experts.
"I certainly recommend people eat together at least a few times a week," said Lola O'Rourke, a Seattle dietitian and spokeswoman for the American Dietetic Association. Doing so helps parents teach kids healthy eating habits, she said, and also gives them some control over what their children eat.
The family meal may be more important than ever, experts say, especially in the wake of a government study released earlier this month that found high-calorie, low-nutrient junk food readily available in nine out of 10 U.S. schools.
In their study on family dinners, Dr. Abdullah A. Mamun, of the University of Queensland in Brisbane, Australia, and colleagues evaluated data on nearly 3,800 children, half girls and half boys, following them from birth to age 14.
They found the prevalence of overweight at age 14 was 24.1 percent for the boys and 27.1 percent for the girls.
They also looked at whether or not families ate together regularly, and quizzed mothers on their attitudes towards the family meal.
While 79 percent of the mothers said their family ate together at least once a day, only 43 percent said they felt it was important to eat together, the Australian team found.
Then the researchers focused on the children of mothers who didn't say it was important to eat together. According to the study, those children were 30 percent more likely to be overweight by age 14 compared with kids born to moms who valued the family meal.
The researchers found no association between the mothers' report of how often the family actually did eat together and the chances of the teen being overweight by age 14, however.
So why might a mother's attitude to family meals matter, even when her family often fails to get together for lunch or dinner? Researchers speculate that maternal attitudes towards the importance of family meals may reflect a broader respect for good nutrition. This might extend to practices such as keeping healthy foods in the house or limiting the amount of times their children can eat "junk food."
That interpretation makes sense to O'Rourke. "You would think people who are more concerned about family meals are also probably more concerned about nutrition," she said.
Mothers who encourage family dinners may also be providing more emotional support to their teens, she said, or building self-confidence in them so they are less likely to turn to food for stress-relief.
"In the past we have seen [in research] that a higher incidence of family meals is associated with a better nutrient intake, healthier meals," she said.
Eating together as a family, at least a few times a week, gives everyone a chance to connect, she said, and "parents have more influence in terms of what is being put on the table."
Parents can also take the opportunity to discuss healthy eating habits and set guidelines for eating at school, where junk food is common. A study released in early September by the Government Accountability Office, the investigative arm of Congress, found that nine out of 10 schools have candy, soda, pizza and other snacks readily available, and that schools are one of the largest sources for unhealthy food for today's children.
In the sample, the GAO surveyed 656 schools, with 51 percent of the principals responding. Vending machines were available in nearly all high schools and middle schools but less than half of elementary schools. Junk food has become more common in middle schools in the past five years, the survey found. And the investigators found that vending machine foods and "junk foods" offered in a-la-carte lines in school cafeterias are crowding out healthier choices.
The result? Obesity among children and teens has more than doubled in the past three decades, according to experts at the Institute of Medicine.
Parents can set guidelines for making good choices at school, however.
"Don't tell them they absolutely can't have pizza or whatever it is [they want to eat]," O'Rourke said. "Saying no you can't have it at all will backfire." Rather, she suggested, ask them to limit foods such as pizza to once a week or so at school.
Another good idea, O'Rourke said, is to "create these foods at home in healthier versions, such as pizza with less cheese, using whole wheat crust and more veggies as toppings."
More information
To learn more about healthy eating for children, visit the U.S. Department of Agriculture.
