Even A little Extra Body Fat May Be Harmful In Youth

Obesity and Youth

Excess body fat early in life may have adverse cardiovascular effects, even in children and adolescents who aren't obese or overweight, researchers suggest in Circulation: Journal of the American Heart Association.

In the study, researchers found that adiposity (fat) in body tissue was associated with reduced blood vessel distensibility, an early marker of cardiovascular disease. Distensibility is a measure of the elasticity of blood vessels. Ultrasound is used to measure distensibility. In young teenagers, excess fat was more strongly associated with the reduction in arterial distensibility than was cholesterol and other blood fats. "These observations emphasize the importance of population-wide strategies to reduce childhood adiposity by a combination of changes in diet and physical activity," said Peter H. Whincup, Ph.D., of the Division of Community Health Sciences, lead author of the study and Professor of Cardiovascular Epidemiology at St. George's.

In the past, classic heart disease risk factors, such as high cholesterol and high blood pressure, were uncommon in childhood. However, obesity and associated risk factors have become increasingly common in children and adolescents and is epidemic in some Western countries.

Reduced distensibility predicts adverse cardiovascular outcomes in adults. Obesity in adults is associated with a clustering of heart disease risk factors (including high blood pressure, cholesterol abnormalities and insulin resistance) known as metabolic syndrome. Childhood adiposity has a similar adverse effect on metabolic factors, but the impact of excess fat in childhood, and the associated metabolic changeson heart and blood vessel disease have not been studied extensively.

It has previously been shown that severe obesity in teenagers is associated with abnormal activity of the endothelium (the thin lining of blood vessel walls), and reduced arterial distensibility. High cholesterol levels have a similar association in children who have not yet reached puberty. With that background, the researchers studied the association of adiposity and its associated metabolic disorders with arterial function and compared the relationship to that of other heart disease risk factors.

The study involved 471 children, 13-15 years old, who had their blood pressure, lipids, insulin and skin-fold thickness (an indication of body mass and fat accumulation) measured. Researchers used ultrasound to determine the arterial distensibility of the brachial artery in the arm. Some children (152) had undergone similar evaluations when they were 9 11 years old, allowing the investigators to study the effects of heart disease risk factors over time.

When the researchers examined different components of the metabolic syndrome, they found that insulin resistance, diastolic blood pressure (the second number in a blood pressure measurement), and the number of components of the metabolic syndrome present in a child were also associated with arterial distensibility. C-reactive protein, a marker of inflammation, also was inversely correlated with distensibility. LDL (bad cholesterol), HDL (good cholesterol), triglycerides (a type of blood fat), systolic blood pressure, and blood glucose had either a minor or no effect on distensibility.

An evaluation of the interaction between risk factors showed that adiposity was related to blood pressure, total cholesterol, LDL and insulin resistance. These associations partly explained the impact of body fat accumulation on distensibility.

Analysis of data on the children evaluated at ages 9-11 and 13-15 showed that the relationship of cholesterol and blood pressure with distensibility was present at both time periods. In contrast, the relationship between body mass index (BMI, a measure of obesity) and insulin resistance appeared only at the later time period.

Though high levels of LDL (bad cholesterol) are related to lower distensibility, HDL (good cholesterol), triglycerides (another type of blood fat), systolic blood pressure, and blood glucose had either a minor or no effect on distensibility.

The impact of adiposity appeared stronger than the previously documented association between cholesterol and distensibility, Whincup said.

The researchers noted that the effects of adiposity on arterial distensibility occurred at BMI levels well below those considered to represent obesity.

The results suggest that arterial distensibility may provide a valuable marker for detecting the early cardiovascular consequences of adiposity in future studies researching adiposity's impact and reduction in young people, Whincup said.

Researchers suggest using a combination of diet and exercise as important strategies to combat adiposity in children and young adults.