Date of Graduation


Document Type


Degree Type



Davis College of Agriculture, Natural Resources and Design


Human Nutrion and Foods

Committee Chair

Melissa Ventura-Marra

Committee Co-Chair

Matthew J Delmonico

Committee Member

Christa L Lilly


Middle-aged adults suffer from the highest rates of obesity in the nation. Obesity is not only a risk factor for cardiovascular-related chronic disease, it is also associated with decreased functional status in aging populations. Depletion of lean mass is a concerning consequence of intentional weight loss. However, efforts to attenuate loss of lean mass with weight loss are often limited to older adults. Understanding body composition changes that occur during intentional weight loss and factors to limit the loss of lean mass during weight loss in middle aged adults are needed reduce and prevent adverse outcomes in old age. The objectives of this study were 1) to describe changes in body composition among obese middle-aged and older males completing a 12 week weight loss study and 2) to determine the association between dietary protein and changes in fat-free mass (FFM) and skeletal muscle mass (SMM) during weight loss. Participants were middle-aged and older males with at least one cardiovascular risk factor completing a 12 week energy restricted weight loss pilot (n=55; age= 59.6 +/- 7.6 years; BMI= 36.6 +/- 5.8 kg/m2). Participants were classified as losing ≥ 3 or < 3% of baseline body weight (weight loss and weight stable, respectively). Body composition changes were assessed by multi-frequency, segmental bioelectrical impendence analysis. Diet was assessed from 4-day diet record collected at weeks 0, 6 and 12. The association between dietary variables and changes in FFM and SMM was examined using Spearman's rho. Weight loss participants lost an average of -8.42 +/- 3.82 kg, with a -2.52 +/- 2.11kg reduction in FFM. SMM was reduced by an average of -1.86 +/- 1.17 kg. Energy restriction did not significantly protein intake (р>0.05). Increased of weight loss and caloric restriction were associated with increased loss of SSM (&rgr; = 0.43; p< 0.01 and &rgr;= 0.75; p<0.01, respectively). Understanding body composition changes during intentional weight loss in middle aged and older males is key to developing ideal weight loss strategies. Significant, but usual body composition changes occurred with intentional weight loss. Protein intake was not related to changes in muscle mass in this sample, however, dietary strategies to limit lean mass depletion during energy restriction require further exploration.