We thank Dr. Rasmussen for this comment and appreciate his concern, which primie facie has apparent merit. However, we contend that it is unlikely that our findings depend on the choice of study participants and are therefore limited in significance to obese, older adults with little significance to the general older adult population.

First, approximately 35-40 % of US adults aged 65 - 80 years are overweight (with a BMI between 25 and <30 kg/m2) and another 20-25% are obese (BMI ≥30 kg/m2) [see Li F, Fisher KJ, and Harmer P. Prevalence of overweight and obesity in older U.S. adults: estimates from the 2003 Behavioral Risk Factor Surveillance System survey. J Am Geriatr Soc 53: 737-739, 2005]. Secondly, although our subjects were obese, and somewhat insulin resistant (in terms of glucose metabolism) when compared with normal-weight healthy adults, none were hyperglycemic or had diabetes. A decline in insulin sensitivity is a normal consequence of both obesity and aging. Most importantly, plasma glucose and insulin concentrations were not different in our men and women which in all likelihood excludes the possibility that sex differences were due to differences in insulin sensitivity. Thirdly, the results from our study of sex differences in older adults studied in the basal state have recently been confirmed by Dr. G. Henderson and colleagues at the Mayo Clinic in Rochester, MN, who found that the basal rate of muscle protein synthesis is greater in non-obese women than in non-obese men (presentation at the Experimental Biology meeting in San Diego earlier this year and personal communication with the authors). Unfortunately, the effect of feeding was not evaluated in that protocol.

Thus, we propose that the sex-differences we discovered are not “overstated” and are indeed of significance for the older adult population of the USA. We will certainly look forward to additional studies in this area.