Overweight people who lose a moderate amount of weight get an immediate benefit in the form of better heart health, according to a study conducted at Washington University School of Medicine in St. Louis.
And the heart improvements happen whether that weight is shed by eating less or exercising more.
"If individuals want to do something that's good for their heart, then my message to them is lose weight by the method they find most tolerable," says the study's senior author Sándor J. Kovács, Ph.D, M.D., director of the Cardiovascular Biophysics Laboratory and professor of medicine. "They're virtually guaranteed that it will have a salutary effect on their cardiovascular system."
Studying a group of healthy, overweight but not obese, middle-aged men and women, the researchers found that a yearlong regimen of either calorie restriction or exercise increase had positive effects on heart function. Their analysis revealed that heart function was restored to a more youthful state so that during the heart's filling phase (called diastole) it took less time for participants' hearts to relax and fill with blood. The findings will appear in an upcoming issue of the American Journal of Physiology and are now available online.
"As we get older, our tissues become more fibrotic as collagen fibers accumulate," says study co-author John O. Holloszy, M.D., professor of medicine in the Division of Geriatrics and Nutritional Science. "So the arteries and heart muscle stiffen, and the heart doesn't relax as well after contracting. Similar studies that we've conducted with members of the Caloric Restriction with Optimal Nutrition Society (CRONies) show they have heart function resembling much younger people." CRONies voluntarily consume about 25 percent fewer calories than the average American while still maintaining good nutrition.
The scientists used ultrasound imaging (echocardiography) to measure the diastolic or filling phase of the cardiac cycle because it is a crucial indicator of heart health. "During filling, the left ventricle is a suction pump," Kovács explains. "Think of the rubber bulb of an old-fashioned bicycle horn — you squeeze it (the analog of the ejection phase of the cardiac cycle), then let go (the analog of the filling or diastolic phase) and the rubber bulb springs back to its original shape, sucking air back in. Similarly, the heart's muscle and connective tissue are elastic, and after ejecting blood to the body during contraction (systole), the left ventricle springs back to draw in new blood (diastole). It's during this filling phase of the cardiac cycle that subtle changes in heart health can be most readily detected."
By the end of the yearlong study, both the calorie restriction and exercise groups of volunteers lost 12 percent of their weight and 12 percent of their body mass index (BMI), a measurement considered to be a fairly reliable indicator of the amount of body fat. In both groups, participants' hearts responded to this weight loss by gaining the ability to relax more quickly, recovering some of the elasticity characteristic of younger heart tissue. Those in the calorie restriction group achieved slightly more reduction of heart stiffness.
Cardiologists can measure delicate alterations in diastolic function because of the work of Kovács, also professor of cell biology and physiology and adjunct professor of physics and of biomedical engineering, who developed a methodology called parameterized diastolic filling (PDF) formalism, which analyzes the filling of the heart according to physical laws and determines the chamber's elasticity and stiffness. Previous studies in humans using the PDF formalism have shown that it's a more sensitive and specific predictor of cardiovascular health than conventional indexes of heart function determined by echocardiography.
Although previous studies also have indicated that the heart benefits from weight loss, those studies were performed on morbidly obese people, few focused on diastolic function and none used the sophisticated PDF formalism. By looking at filling function in healthy, non-obese people using PDF formalism, the researchers in the current study were able to understand in more detail how normal hearts react to moderate weight loss.