Obesity study finds cardio plus weight training may be best for teens
Marlene Leung, CTVNews.ca
Published Monday, September 22, 2014 4:03PM EDT
Last Updated Monday, September 22, 2014 6:35PM EDT
A combination of aerobic exercise and resistance training may be the best way to fight teen obesity, a new Canadian study suggests.
In the study, published Monday in the Journal of the American Medical Association Pediatrics, researchers from the University of Calgary and the University of Ottawa randomly placed 304 overweight teens from the Ottawa region into four different groups.
The first group was selected to perform resistance training with weight machines and free weights; the second group performed aerobic exercise on treadmills, elliptical machines and stationary bikes; the third group did both resistance training and aerobic exercise; and a fourth control group didn't do any exercise.
The groups assigned to exercise were given training sessions four times a week for 22 weeks. Several of the sessions were supervised by a personal trainer.
All of the teens were given identical diet counselling before being assigned to one of the four groups. Additional diet counselling was given to all the participants after three and six months.
After six months, the participants' body fat was measured using a magnetic resonance imaging scanner. These results were compared to the measurements taken at baseline. Participants' weight, height, body mass index, blood pressure and waist and hip circumference were also measured. Blood samples were also taken to measure fasting insulin, glucose and certain lipids.
After six months, all three groups assigned to do exercise saw a similar and significant reduction in body fat, compared to the control group that did no exercise and only received diet counselling.
The group that performed both aerobic exercise plus strength training saw an average decrease in their body fat of 1.4 per cent, compared to the group that did aerobic training (1.1 per cent) and the group that did resistance training (1.6 per cent).
But the combined group saw a larger reduction in their waist circumference compared to the other exercise groups, said University of Ottawa researcher Dr. Glen Kenny.
"Remarkably, among participants who completed at least 70 per cent of the prescribed exercise sessions, waist circumference decreased close to seven centimetres in those randomized to combined aerobic plus resistance exercise, versus about four centimetres in those randomized to do just one type of exercise, with no change in those randomized to diet alone," Kenny said in a statement.
"We saw reductions of five to six pounds in terms of fat mass loss. There was greater reduction in body fat and in waist circumference. All of these are very important factors in that they help reduce the risk of developing diabetes, childhood obesity and in diabetes," Kenny said.
Allison Neilson-Sewell, who weighed 320 pounds when she was 18 years old, said she tried a few different diets, but they didn't work.
"At 320 pounds, it just seems overwhelming but if you do 10 pounds at a time it is completely achievable. There is no reason why you cannot do this," Neilson-Sewell said.
"One year after the study I lost over 130 pounds just from walking and running everyday and eating clean, whole foods," Neilson-Sewell added.
The University of Calgary's Dr. Ron Sigal, another of the study's co-authors, said the results will help guide overweight and obese teens who are trying to lose weight.
"Obesity is an epidemic among youth," Sigal said in a statement. "Adolescents who are overweight are typically advised to exercise more, but there is limited evidence on what type of exercise is best in order to lose fat."
The study notes that although teens wanting to lose weight should ideally do both strength training and aerobic exercise, "significant benefit can be achieved through either type of exercise alone."
The researchers hope the study will add to the debate on how to combat obesity in children and teens. It is estimated that 80 per cent of overweight youth typically continue to be obese as adults.