Abstract

The Effect of Exercise on Intramyocellular and Extramyocellular Lipids in Childhood Versus Adulthood onset of Obesity: A Pilot Study
Background: Compared to those who develop obesity in adulthood, those with childhood onset obesity have greater risk of metabolic disease. However, the mechanisms associated with this increased risk are unknown. Muscle lipids have been associated with insulin resistance. Thus, differences in the metabolism of intramyocellular lipids (IMCL) and extramyocellular lipids (EMCL) may contribute to greater risk of metabolic disease in childhood vs. adulthood onset obesity.
Objective: To investigate whether the timing of obesity onset affected the metabolism of IMCL and EMCL in response to exercise in individuals with obesity.
Methods: Ten males with obesity ≥23yrs were recruited with either childhood- (n=5) or adulthood- onset (n=5) obesity. At visit 1, participants underwent dual x-ray absorptiometry (DXA) and resting indirect calorimetry. Participants were provided with a standardized diet for 3 days prior to visit 2. At visit 2, baseline IMCL and EMCL via magnetic resonance spectroscopy (MRS) was measured. Participants then completed a 90 minute cycle with indirect calorimetry. A second MRS measurement was done immediately post exercise.
Results: Substrate oxidation was not significant between groups. Post exercise, the adulthood onset group had a significant (P=0.039) decrease in IMCL, with no change in EMCL. The childhood onset group displayed no change in IMCL or EMCL with exercise.
Conclusion: This was the first study to compare the rates of IMCL and EMCL depletion in childhood and adulthood onset of obesity after a bout of exercise, providing novel insight for future research. We made a novel observation that males with adulthood onset obesity had greater decreases in IMCL post-exercise.