Effects of weight loss and physical activity on muscle lipid content and droplet size

Obes Res. 2004 May;12(5):761-9. doi: 10.1038/oby.2004.92.


Objectives: To address the potential effects of weight loss and physical activity (WL + Ex) on intramyocellular lipid (IMCL) and lipid droplet size in overweight and obese previously sedentary individuals.

Research methods and procedures: IMCL and lipid droplet size was determined in vastus lateralis, obtained by percutaneous biopsy, from 21 obese volunteers (9 men/12 women), using Oil Red O staining, along with succinate dehydrogenase histochemistry and mitochondrial immunohistochemistry as measures of skeletal muscle oxidative capacity. Insulin sensitivity (IS) was determined by glucose clamp.

Results: A 4-month WL + Ex intervention resulted in approximately 10% WL and approximately 15% increase in maximal oxygen uptake, leading to a 46% increase in IS (all p < 0.01). IMCL did not significantly change (p = 0.36). However, the size of lipid droplets decreased after WL + Ex (p < 0.01), and this decrease in lipid droplet size correlated with increased IS (p < 0.01) and the amount of physical activity (p < 0.05). Succinate dehydrogenase activity and mitochondrial labeling increased significantly (p < 0.01), without a significant shift in fiber type distribution.

Discussion: In summary, IMCL does not decrease in response to WL + Ex in obese, previously sedentary individuals, yet the lipid within muscle is dispersed into smaller droplets. This change in the size of lipid droplets, likely coupled with a concomitant increase in oxidative enzyme capacity, is correlated to improved IS.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Biopsy
  • Body Composition
  • Diabetes Mellitus, Type 2 / metabolism
  • Diabetes Mellitus, Type 2 / pathology
  • Exercise*
  • Female
  • Humans
  • Immunohistochemistry
  • Intracellular Space / chemistry
  • Lipids / analysis*
  • Lipids / chemistry*
  • Male
  • Microscopy, Confocal
  • Mitochondria, Muscle / ultrastructure
  • Muscle, Skeletal / chemistry*
  • Muscle, Skeletal / enzymology
  • Muscle, Skeletal / ultrastructure
  • Oxidation-Reduction
  • Oxygen Consumption
  • Particle Size
  • Physical Fitness
  • Succinate Dehydrogenase / metabolism
  • Weight Loss*


  • Lipids
  • Succinate Dehydrogenase