Chronic administration of therapeutic levels of clenbuterol acts as a repartitioning agent.

This study examines how therapeutic doses of clenbuterol, in conjunction with or without exercise, can affect body fat and muscle mass in horses. The study found that clenbuterol changes body composition, showing significant reduction in body fat and an increase in fat-free mass, even more so when combined with exercise.

Objective and Methodology

• The study’s primary aim was to investigate the effects of clenbuterol, a bronchodilator drug typically used in treating respiratory conditions, on body composition. The study also considered the combined effects of clenbuterol and physical exercise.
• 23 unfit Standardbred mares were divided into four groups: the ClenEx group (clenbuterol plus exercise), the Clen group (clenbuterol only), the Ex group (exercise only), and the Con group (control). Body fat and muscle mass changes were subsequently observed and recorded.
• Measurements taken included rump fat thickness (using B-mode ultrasound) and overall body fat percentage, using previously established methods.

Results

• The exercise-only group saw a reduction in body fat starting from the 4th week and a slight increase in Fat-Free Mass (FFM – a measurement of everything in the body excluding all fat) from the 8th week.
• The clenbuterol-only group had significant changes in the 2nd week: body fat percentage and overall fat mass significantly reduced, with a moderate FFM increase.
• The ClenEx group (clenbuterol and exercise) had notable decreases in body fat percentage and overall fat mass as early as the second week, similar to the clenbuterol-only group. However, this group saw a significant increase in FFM by the sixth week.
• The control group showed no changes during the entire research period.

Conclusion

• This research suggests that a combination of exercise and clenbuterol has a cumulative effect for fat loss but produces contrasting results for changes in FFM.
• Interestingly, administering therapeutic levels of clenbuterol resulted in significant “repartitioning”, showing it as an effective tool to adjust body fat and muscle mass.
• The findings suggest clenbuterol might be useful as a weight-loss or body-building agent when administered in measured doses.