Overweight adolescents face the same increased risk of developing heart disorders as their obese counterparts, a conclusion that contradicts the popular idea that the heavier a person is, the higher their cardiovascular risk, reports a new study. The findings of the study are published in the journal Cardiology in the Young.
The results of cardiovascular fitness tests with volunteers aged 10-17 were similar in both groups.
"Until recently, overweight in adolescence wasn't considered as important risk as obesity for the development of the cardiovascular disease. We found the risks to be similar in both cases," Vitor Engrácia Valenti told. Valenti is a professor at the UNESP campus in Marília and was the principal investigator for the project.
The participants performed a moderate exercise protocol, which involved walking on a treadmill at a slope of 0% and required 70% of the maximum estimated heart rate for this age group.
Heart rate variability was measured before and after the exercise session to assess the speed of autonomic cardiac function recovery. Prolonged autonomic nervous system imbalances after physical exertion have been shown to increase the risk of an acute event and future cardiovascular disease.
During the first few seconds of an exercise session, the parasympathetic nervous system decelerates cardiac function. One of the two main divisions of the autonomic nervous system, this system conserves energy by slowing the heart rate and relaxing the body in other ways. After 50-60 seconds, the sympathetic nervous system kicks in, stimulating activity such as increased heart rate via adrenalin release, that prepares the body to react to a stressful situation.
According to Valenti, studies published in recent years have shown that the longer after a period of exertion the autonomic nervous system takes to stabilize, so that heart rate returns to normal, the greater the risk of cardiovascular or metabolic disease.
The researchers found no significant difference in heart rate variability between overweight and obese adolescents or between girls and boys.
"The mean autonomic nervous system variables were practically identical for both groups regardless of sex," Valenti said.
"These findings suggest that overweight adolescents have the same predisposition or vulnerability as that of obese adolescents to cardiovascular diseases such as hypertension and heart failure, as well as to metabolic disorders such as diabetes, dyslipidemia, and high levels of triglycerides and LDL cholesterol."
The number of obese adolescents worldwide has risen sharply in the last 40 years. According to recent studies, the proportion increased between 30% and 50% per decade in developed countries in Brazil, and the prospects are the same.