Letters Section Editor: Stephen J. Lurie,
MD, PhD, Senior Editor.
To the Editor: Dr Jakicic and colleagues1 concluded that vigorous exercise intensity was
not superior to moderate exercise intensity for weight loss in a 12-month
physical activity program with additional restriction in dietary fat and caloric
To help explain this unexpected finding, we suggest that the intensity-dependent
effect of physical activity on body composition should be taken into account.
A higher intensity level of physical activity leads to a more pronounced shift
in the relationship of fat mass with fat-free mass (specifically, skeletal
muscle mass) with only minimal changes in body weight.2,3 Thus,
the apparent lack of an effect of intensity may be due to higher postintervention
fat-free mass in the individual who exercised vigorously. This potential benefit
of higher exercise intensity could have been assessed with measurement of
Ritt M, Lechleitner M. Effect of Exercise Intensity on Body Composition—Reply. JAMA. 2003;290(23):3069. doi:10.1001/jama.290.23.3069-a