Deborah Bujnowski, PhD, MPH, RD: University of North Carolina (UNC) Pengcheng Xun, MD, PhD: UNC

1. Longitudinal Association Between Animal and Vegetable Protein Intake and Obesity among Adult Males in The United States: The Chicago Western Electric Study Deborah Bujnowski, PhD, MPH, RD: University of North Carolina (UNC) Pengcheng Xun, MD, PhD: UNC Martha L. Daviglus, MD, PhD: Northwestern University (NU) Linda Van Horn, PhD, RD: NU Ka He, MD, ScD: UNC Jeremiah Stamler, MD: NU

2. Longitudinal Association Between Animal and Vegetable Protein Intake and Obesity among Adult Males in The Unites States: The Chicago Western Electric Study Study overview Background • Although weight loss diets that promote higher intake of protein and restrict intake of carbohydrates are popular, data on protein intake and body weight remain inconsistent. • Most studies that investigate protein intake and body weight have limited follow-up data ranging from several weeks to one year; few studies extend follow-up to two years or longer • Very long-term data on protein intake and body weight are lacking. • In addition, none of these studies examined animal protein and vegetable protein separately. Given their differences in amino acid composition , vegetable and animal protein may have different effects on body weight.

3. Longitudinal Association Between Animal and Vegetable Protein Intake and Obesity among Adult Males in The Unites States: The Chicago Western Electric Study BMI & Psychosocial measures Study Objective • To prospectively examine the long-term association of protein (total, animal, and vegetable) intake with overweight and obesity among middle-aged male employees of the Chicago Western Electric Company.

4. Longitudinal Association Between Animal and Vegetable Protein Intake and Obesity among Adult Males in The Unites States: The Chicago Western Electric Study Correlation matrix Study Design • Prospective cohort study • 2107 employed men ages 40-55 years at baseline in 1957-1958, designed primarily to examine coronary heart disease and its predictors • Participants held positions for at least two years related to telephone manufacturing • Exclusions: • Missing data on diet (n = 187) or education (n = 42) • Not completed at least four (of seven) follow-up examinations (n = 148) • A total of 1730 men remained for analysis.

5. Correlation matrix Longitudinal Association Between Animal and Vegetable Protein Intake and Obesity among Adult Males in The Unites States: The Chicago Western Electric Study Methods • Dietary intake data were collected twice by two nutritionists at baseline in 1957-58 and initial follow-up examination one year later. • Mean nutrient intake data from the two examinations were used to reduce measurement error. • Standardized interviews and questionnaires were completed according to Burke’s comprehensive dietary history method. • The outcomes were overweight and obesity at a given examination, defined as BMI > 25.0 kg/m2 and BMI > 30.0 kg/m2, respectively. • Generalized Estimating Equation (GEE) for longitudinal data was used to examine the associations between protein intake (animal, vegetable, and total protein) and overweight/obesity. • All analyses were performed using SAS version 9.1.3 .

6. Correlation matrix Longitudinal Association Between Animal and Vegetable Protein Intake and Obesity among Adult Males in The Unites States: The Chicago Western Electric Study 8 Total <0.01 6 Animal <0.01 Vegetable 0.053 OR (95%CIs) 4 2 0 Q1 Q2 Q3 Q4 Protein intake Main results: Multivariable adjusted odds ratios (95%CIs) of obesity Ptrend

7. Figure Longitudinal Association Between Animal and Vegetable Protein Intake and Obesity among Adult Males in The Unites States: The Chicago Western Electric Study Strengths and limitations • Main strength: • relatively long-term follow-up period with annual examinations throughout. • fairly homogeneous cohort (all men, of similar ethnic backgrounds, and employed in similar work settings with comparable levels of occupational activity), tending to reduce likelihood of confounding from unmeasured factors associated with both protein intake and body weight. • Limitations: • Lack information about physical activity

8. Figure Longitudinal Association Between Animal and Vegetable Protein Intake and Obesity among Adult Males in The Unites States: The Chicago Western Electric Study Conclusion • Animal protein intake was positively related to and vegetable protein intake was inversely associated with body mass and overweight/obesity, independent of other dietary macronutrients, in a cohort of American adult men studied longitudinally for seven years. • Animal and vegetable protein appear to play different roles in obesity development; replacing animal protein with vegetable protein in the diet may offer promise in future prevention/weight control interventions • Additional observational and interventional long-term studies of protein type and weight change are warranted, and should examine protein in the context of overall diet including other macronutrients