Researchers looked the relationship between BMI and routinely collected cardiovascular data, such as blood pressure and heart rate, in more than 3,000 17-year-olds born in the 1990s. They also examined cardiovascular scans from 400 21-year-olds who were at higher genetic risk for an unhealthy BMI.
“Our results suggested that having a higher BMI likely causes higher blood pressure,” said lead study author Kaitlin Wade of the University of Bristol in the UK. The results also suggest that a higher BMI causes so-called left ventricular mass index to be higher, reflecting enlargement of the left ventricle in the heart, which pumps blood around the body, she said.
“These findings suggest that BMI is likely to have an adverse causal impact on cardiac structure even in young adults,” Wade said by email. “Our results support efforts to reduce BMI to within a normal, healthy range from a young age to prevent later cardiovascular disease.”
A BMI of 18.5 to 24.9 is considered healthy, 25 to 29.9 is overweight, 30 or above is obese and 40 or higher is morbidly or extremely obese.
In the current study, the 17-year-olds with weight data available had an average BMI of about 23, in the healthy range, and average blood pressure readings of about 119 mmHG over 64 mmHG, also within a healthy range.
The American Heart Association defines hypertension, or high blood pressure, as a systolic reading of 130 mmHg or higher and diastolic readings of 80 mmHg or higher. Systolic pressure reflects the pressure blood exerts against artery walls when the heart beats. Diastolic pressure indicates the pressure when the heart rests between beats.
Among the young adults in the current study, higher BMIs were associated with an increased risk of high blood pressure, researchers report in Circulation.
The study wasn’t a true controlled experiment designed to prove whether or how excess weight might directly cause heart problems.
Still, the results suggest that heavier young adults had hearts that pumped a greater volume of blood each minute, which over time can lead to high blood pressure and thickening of the heart muscle, noted Dr Holly Gooding, a researcher at Harvard Medical School in Boston who wasn’t involved in the study.
“Whether this is due to the increased metabolic demands of their higher weight, or increased inflammation generated by the fat cells themselves, or something else is unclear, as these mechanisms weren’t addressed in this study,” Gooding said
“What we do know is that it is not simply due to lower physical activity or less optimal dietary patterns in these individuals, as these lifestyle factors were not associated with the genes for BMI,” she added.
No matter what they weigh, young people can still take steps to minimise their risk of heart attacks and other cardiovascular problems, Gooding added.
“Everyone can protect their heart by staying physically active, eating a diet rich in fruits and vegetables and whole grains and low in sodium and added sugars, and avoiding smoking,” Gooding said. “These health behaviours are important regardless of one’s weight status.”