Physical activity intensity and type 2 diabetes risk in overweight youth: a randomized trial

Int J Obes (Lond). 2016 Apr;40(4):607-14. doi: 10.1038/ijo.2015.241. Epub 2015 Nov 30.


Background: The chronic effects of high-intensity endurance training on metabolic health outcomes in overweight adolescents remains poorly understood.

Objective: To test the hypothesis that high-intensity endurance training (ET) is superior to moderate-intensity ET for improving risk factors for type 2 diabetes in overweight adolescents.

Design and methods: In this randomized trial, 106 overweight and obese adolescents (15.2 years; 76% female; 62% Caucasian) were randomly assigned to high-intensity ET (70-85% of heart rate reserve, n=38), moderate-intensity ET (40-55% heart rate reserve; n=32) or control for 6 months (n=36). The primary and secondary outcome measures were insulin sensitivity assessed using a frequently sampled intravenous glucose tolerance test and hepatic triglyceride content with magnetic resonance spectroscopy. Exploratory outcomes were cardiorespiratory fitness, physical activity and MRI and dual x-ray absorptiometry-derived measures of adiposity.

Results: The study had 96% retention and attendance was 61±21% and 55±24% in the high- and moderate-intensity ET arms. Intention-to-treat analyses revealed that, at follow-up, insulin sensitivity was not different between high-intensity (-1.0 mU kg(-1) min(-1); 95% confidence interval (CI): -1.6, +1.4 mU kg(-1) min(-1)) and moderate-intensity (+0.26 mU kg(-1) min(-1); 95% CI: -1.3, +1.8 mU kg(-1) min(-1)) ET arms compared with controls (interaction, P=0.97). Similarly, hepatic triglyceride at follow-up was not different in high-intensity (-1.7% fat/water (F/W); 95% CI: -7.0, +3.6% F/W) and moderate-intensity (-0.40% FW; 95% CI: -6.0, +5.3% F/W) ET compared with controls. Both high intensity (+4.4 ml per kg-FFM (fat-free mass) per minute; 95% CI: 1.7, 7.1 ml kg-FFM(-1) min(-1)) and moderate intensity (+4.4 ml kg-FFM(-1) min(-1); 95% CI: 1.6, 7.3 ml kg-FFM(-1) min(-1)) increased cardiorespiratory fitness, relative to controls (interaction P<0.001).

Conclusions: ET improves cardiorespiratory fitness among obese adolescents; however, owing to lack of compliance, the influence of exercise intensity on insulin sensitivity and hepatic triglycerides remains unclear.

Publication types

  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Body Mass Index
  • Canada
  • Cardiovascular Physiological Phenomena
  • Diabetes Mellitus, Type 2 / etiology
  • Diabetes Mellitus, Type 2 / physiopathology*
  • Diabetes Mellitus, Type 2 / prevention & control
  • Exercise Therapy*
  • Female
  • Humans
  • Insulin Resistance
  • Male
  • Patient Compliance
  • Pediatric Obesity / blood
  • Pediatric Obesity / complications
  • Pediatric Obesity / physiopathology*
  • Physical Endurance*
  • Physical Fitness
  • Resistance Training
  • Risk Factors
  • Treatment Outcome
  • Triglycerides / analysis
  • Triglycerides / blood


  • Triglycerides