RESEARCH: Men with childhood onset obesity burn less muscle fat during endurance exercise

People who develop obesity in childhood face a greater risk of metabolic diseases than those who gain weight later in life. However, the reasons behind this difference remain unclear. A new study led by Sylvia Santosa, a professor in the Department of Health, Kinesiology and Applied Physiology, investigates how the timing of obesity onset affects the way the body uses fat stored in muscle during exercise.

Researchers recruited 10 men — five with childhood-onset obesity (CO) and five with adulthood-onset obesity (AO). Participants underwent body composition analysis and metabolic testing before cycling for 90 minutes at moderate intensity. Using advanced imaging techniques, the researchers measured changes in intramyocellular lipids (IMCL) — tiny fat droplets stored inside muscle cells that serve as an energy source during exercise.

The results revealed a key difference: only the AO group showed a reduction in IMCL after exercise. This decline is typically seen in lean individuals, indicating efficient fat metabolism. In contrast, the CO group did not show this response, suggesting they may have a reduced ability to use muscle fat for energy. These findings provide new insights into how early-life obesity impacts long-term metabolic health.

The study was published in the International Journal of Obesity, a Nature publication.