Children of obese parents are at high risk for heart conditions later in life. What can be done to lower this risk?
A recent study found that taking breaks during inactivity lowered the risk of heart disease and diabetes in children with a family history of obesity.
The researchers also found that the risk of disease was more closely related to surfing the internet, playing video games and watching television during periods of inactivity than the length of the inactivity itself.
The lead author of this study was Travis John Saunders from the Healthy Active Living and Obesity Research Group of the Children's Hospital of Eastern Ontario Research Institute and of the School of Human Kinetics at the University of Ottawa — both located in Ottawa, Ontario, Canada.
This study used participant data from a previous study called the Quebec Adiposity and Lifestyle Investigation in Youth (QUALITY) study conducted in 2005 to 2008.
The current study used data on 522 children, all of whom were between the ages of 8 and 11 when they enrolled in the QUALITY study. There were 286 boys with an average age of 9.2 years old and 236 girls with an average age of 9.1 years old.
All of these children were white and had at least one parent with confirmed obesity.
The researchers evaluated cardiometabolic risk factors (risk of heart disease and diabetes) such as insulin level, glucose (blood sugar) level, 'good' cholesterol level and blood pressure in each participant. Height, weight and waist size were also measured.
A person has an increased cardiometabolic risk if they have high blood pressure, high glucose, low levels of good cholesterol and a large waist size.
Over the course of a week, the participants were asked to wear an accelerometer any time they were awake — except when they bathed or took part in water activities such as swimming — for at least 10 hours per day for at least four days out of the week, one of which had to be a weekend day.
An accelerometer measures levels of activity by keeping a 'count' that increases as a person's movements go faster.
Sedentary behavior was defined as all the minutes when a participant's accelerometer counted less than 100 counts per minute, and a sedentary bout was the amount of minutes spent in sedentary behavior. Light physical activity (LPA) was defined as the amount of minutes when the accelerometer counted 100 to 2,296 counts per minute, and moderate-to-vigorous activity (MVPA) was defined by the amount of minutes when the accelerometer counted greater than 2,296 counts per minute.
In addition, the participants were given a survey to self-report their daily television viewing time and time spent surfing the internet, playing video games and doing similar activities during the study week.
The findings showed that all the participants averaged 6.5 days using the accelerometer.
The boys averaged 61.2 minutes of MVPA per day, compared to 41.2 minutes per day for the girls. The boys also spent more of their leisure time playing computer and/or video games, with boys averaging 1.1 hours per day versus the girls with 0.6 hours per day.
The researchers also found that the boys had higher glucose and cholesterol levels than the girls, as well as lower levels of blood fats, insulin and blood pressure.
Overall, there were no differences in age, amount of sedentary behavior, amount of light physical activity, television viewing time, total cardiometabolic risk scores or body measurements between the boys and the girls.
The boys were found to have 67 sedentary bouts between one and four minutes per day versus 70 for the girls. However, both boys and girls had 13 sedentary bouts of five to nine minutes per day, four sedentary bouts of 10 to 14 minutes per day, three sedentary bouts of 15 to 29 minutes per day and two sedentary bouts of 30 or more minutes per day.
The researchers found that breaks in sedentary time, and amount of one-to-four-minute sedentary bouts were associated with reduced cardiometabolic risk and lower body mass index (weight to height ratio) in both the boys and the girls.
Sedentary bouts lasting five to nine minutes were associated with smaller waist sizes in the girls. For boys, the number of sedentary bouts lasting 10 to 14 minutes was associated with higher blood sugar levels in girls and higher body mass index in boys.
The findings also revealed that leisure time spent on the computer or playing video games was associated with a higher and continuous cardiometabolic risk, a greater waist size and a lower cholesterol level in boys; and television viewing was associated with a higher and continuous cardiometabolic risk, greater waist size and higher body mass index for the girls.
These researchers concluded that more breaks in sedentary time, with shorter sedentary bouts, were associated with a lowered cardiometabolic risk in children ages 8 to 11, regardless of total sedentary time and physical activity.
In addition, the findings suggested that sedentary behavior in itself did not necessarily affect cardiometabolic risk, but rather what a person did during the sedentary time.
The authors noted some limitations of their study.
First, computer/video sedentary behaviors were self-reported. Second, the accelerometer may have accidentally counted LPA as sedentary behavior. Third, the findings were based on white children with a family history of obesity and therefore may not be applicable to the general population.
This study was published in the November edition of PLoS One.
The Canadian Institutes of Health Research, the Heart and Stroke Foundation of Canada and Fonds de la Recherche en Sante´ du Que´bec provided funding.