Jul 21 2005
Maintaining a healthy weight in children may be one good way to keep a healthy blood lipid profile and a happy heart, a new study has found.
A study of 400 high school age children with a variety of fitness and fatness levels showed that fatter youths had unfavorable lipid profiles, including higher levels of triglycerides and higher ratios of total cholesterol to the protective HDL cholesterol or high density lipoprotein.
"This ratio tells about the balance of the 'bad' to the 'good' forms of lipoproteins; thus a high ratio indicates high risk for coronary artery disease later in life," says Dr. Bernard Gutin, exercise physiologist and Professor Emeritus of Pediatrics and Physiology at the Medical College of Georgia. Dr. Gutin is lead author on the study in the July issue of Pediatric Research.
The study, which included extensive measurement of fitness and fatness as well as fasting blood tests of lipid levels, showed the leanest teens – those with less than 25 percent body fat – had the best lipid/lipoprotein profiles.
Interestingly, fatness had almost no impact on the triglyceride and total cholesterol levels of black teens in the study, a finding researchers say they will pursue further.
"The first issue is that fatness is important," says Dr. Gutin. "Fitness is important too but when you put them together it looks like fatness is more important in teens. The second issue is that the impact of high levels of fatness on triglycerides and total cholesterol seems to be less strong for blacks than it is for whites."
"The take home message is that another good reason to watch your child's weight is his lipid profile," says Dr. Paule Barbeau, MCG exercise physiologist and a study co-author. She and Dr. Gutin note that studies at MCG's Georgia Prevention Institute and elsewhere have shown that the best way to help growing children get and maintain a healthy body composition is physical activity, especially activity of a vigorous nature. Dr. Gutin was a member of a recent national panel of experts, convened by the Centers for Disease Control and Prevention, that said school-age children need an hour or more of moderate to vigorous physical activity daily. Dr. William B. Strong, Section Chief of Pediatric Cardiology Emeritus at MCG, co-chaired the panel.
The foundation for being an adult with cardiovascular disease begins in childhood with genetics, weight, stress and activity level each playing a role, the researchers say. "We think the atherosclerotic process, the building up of fat and other material in the artery wall that ultimately ends up causing a heart attack when the person is in his 40s, 50s or 60s, starts in childhood," says Dr. Gutin.
"This new study reinforces the idea that intervention programs in children should focus on decreasing fatness," says Dr. Barbeau. That focus should begin before a child is born, with a pregnant woman eating right and staying active to help ensure the baby is born at a healthy weight, she says.
MCG researchers say there is evidence that fatter adults tend to have bad lipid profiles and that fitness and fatness influence those profiles.
They wanted to know whether this also is true in children.
Their study indicates that while fatness and a bad lipid profile seem to have a direct correlation, especially in white teens, fitness likely has an indirect role because it influences fatness. "Fitness doesn't seem to have an independent effect on these children," Dr. Barbeau says. But it likely is part of an unhealthy cycle that fat children tend to be less physically active so they get fatter, she says.
The study also indicates dramatic differences in the impact of fatness on the lipid profile of black and white teens. There is some evidence black adults tend to have a better lipid profile than white adults as well as a lower incidence of early heart attack, notes Dr. Gutin. A bad lipid profile is tied to early cardiovascular disease. On the other hand, blacks are at increased risk for hypertension early in life. Dr. Gregory Harshfield, a hypertension researcher and colleague of Drs. Gutin and Barbeau, has shown that a decreased ability to eliminate sodium following stress, may be one reason why.
"It looks like there may be different mechanisms by which some blacks and whites develop hypertension and probably cardiovascular disease," says Dr. Barbeau. "A bad lipid profile may not be the most important mechanism for blacks."
The study also found that easy, inexpensive and widely available ways to measure fatness seem to work just fine. Researchers assessed body mass index by using a relatively simple calculation that involves height and weight as well as measuring waist circumference. They also used the more expensive dual energy X-ray absorptiometry, or DXA, which enables much more precise measures of bone, muscle and fat. The finding that the widely available approaches work well is good news for physicians who want to keep up with children's fatness levels but don't have DXA technology available to them, Dr. Gutin says.