Kids’ unhealthy lifestyles, typically including poor diets and a lack of physical activity may not only contribute to the ever-growing obesity epidemic, but also increasing resting pulse rates. According to a recent study, the average resting pulse rate of U.K. children has increased an average of two beats per minute (bpm) in the past 30 years, elevating their risk for heart disease and diabetes in adulthood.

A resting pulse rate is an important indicator of an individual’s physical fitness and cardiovascular health, and is positively associated with adiposity levels, or fat, in children. Medline Plus says the normal heart rate for children between the ages of 9 and 11 ranges between 60 bpm and 95 bpm, while 60 to 100 bpm is the average rate for children 10 years and older, and adults.

An individual’s heart rate changes from minute to minute. Factors that influence a person’s rate includes standing up or lying down, moving around or sitting still, and being stressed or relaxed. Other influential uncontrollable factors include genes and aging. However, individuals who experience a fast heart rate unrelated to the factors listed above may be faced with a more serious health problem. A high heart rate is commonly a marker of sympathetic nervous system activity which is associated with heart disease, atherosclerosis (hardening of the arteries), and arrhythmia (an irregular heartbeat).

British researchers sought to investigate whether levels of physical fitness have changed in children by examining the resting pulse rate among children in the U.K. Over 22,000 kids between the ages of 9 and 11, who were a part of five population-based studies conducted in the U.K. between 1980 and 2008, took part in the study.

Boys’ pulses were found to rise by 0.07 bmp each year over the course of the study to reach an average of 78.7 bpm, while girls’ experienced an increased pulse rate of 0.03 bpm per year, reaching 82.2 bpm. Overall, since the 1980s, this age group’s average heart rate was found to increase by two bpm for boys and one bpm for girls, with the fastest increases occurring after the mid-1990s.

"If an increase of two beats per minute in mean resting pulse rate in boys persists to the adult population, this could result in a four percent increase in coronary heart disease mortality among healthy men and a two percent increase in risk of developing diabetes among those over 65 years," wrote the researchers.

To examine whether the childrens’ body mass index (BMI) contributed to the rise in resting heart rates, researchers measured BMI throughout the study period. For boys, BMI accounted for only 13.8 percent of increased pulse rate, while it accounted for 17.2 percent among girls.

"Although modest, it is important to monitor these trends (in resting pulse rate), especially in boys, as they appear to have increased at a faster rate in recent years," the researchers concluded. "Increases in physical activity in children would have a beneficial effect on their physical fitness and cardiovascular health while reducing resting pulse rate."

The researchers suspect while the rise of resting heart rates is likely due to the growing obesity crisis, the figures of body weight in the study could not solely justify the rapid increase.

The Centers for Disease Control and Prevention says childhood obesity has more than doubled in children and tripled in adolescents over the past 30 years. The percentage of U.S. children between the ages of 6 and 11 who were obese increased from 7 percent in 1980 to almost 18 percent in 2010. Children and adolescents who are obese are more likely to be obese as adults and therefore at a higher risk for heart disease, type 2 diabetes, stroke, several types of cancer, and osteoarthritis.

The decrease in the amount of physical activity in this age group and the increase in adopting sedentary lifestyles has contributed to the obesity epidemic, and quite possibly a high resting heart rate — both associated with poor fitness.

While physical inactivity could lead to higher heart rates, the researchers suggest for adolescents and parents to monitor their heart rate and keep it as a normal, moderate pace, respectively.

To learn about the ways to increase physical activity in children, click here.

Source: Cook DG, Law C, Li L et al. Trends In Resting Pulse Rates In 9-11 Year Old Children In The UK 1980-2008. Arch Dis Child. 2013.