Associations between macronutrient intake and self-reported appetite and fasting levels of appetite hormones: results from the Optimal Macronutrient Intake Trial to Prevent Heart Disease.

The authors compared effects of macronutrients on self-reported appetite and selected fasting hormone levels. The Optimal Macronutrient Intake Trial to Prevent Heart Disease (OMNI-Heart) (2003-2005) was a randomized, 3-period, crossover feeding trial (n = 164) comparing the effects of 3 diets, each rich in a different macronutrient. Percentages of kilocalories of carbohydrate, fat, and protein were 48, 27, and 25, respectively, for the protein-rich diet; 58, 27, and 15, for the carbohydrate-rich diet; and 48, 37, and 15 for the diet rich in unsaturated fat. Food and drink were provided for each isocaloric 6-week period. Appetite was measured by visual analog scales. Pairwise differences between diets were estimated using generalized estimating equations. Compared with the protein diet, premeal appetite was 14% higher on the carbohydrate (P = 0.01) and unsaturated-fat (P = 0.003) diets. Geometric mean leptin was 8% lower on the protein diet than on the carbohydrate diet (P = 0.003). Obestatin levels were 7% and 6% lower on the protein diet than on the carbohydrate (P = 0.02) and unsaturated-fat (P = 0.004) diets, respectively. There were no between-diet differences for ghrelin. A diet rich in protein from lean meat and vegetables reduces self-reported appetite compared with diets rich in carbohydrate and unsaturated fat and can be recommended in a weight-stable setting. The observed pattern of hormone changes does not explain the inverse association between protein intake and appetite.

Is protein intake associated with bone mineral density in young women?

BACKGROUND: The range of protein intakes for optimizing bone health among premenopausal women is unclear. Protein is a major constituent of bone, but acidic amino acids may promote bone resorption. OBJECTIVE: The objective was to examine cross-sectional and longitudinal associations between baseline dietary protein and bone mineral density (BMD) among 560 females aged 14-40 y at baseline enrolled in a Pacific Northwest managed-care organization. The role of protein source (animal or vegetable) and participant characteristics were considered. DESIGN: Dietary protein intake was assessed by using a semiquantitative food-frequency questionnaire in participants enrolled in a study investigating associations between hormonal contraceptive use and bone health. Annual changes in hip, spine, and whole-body BMD were measured by using dual-energy X-ray absorptiometry. Cross-sectional and longitudinal associations between baseline protein intake (% of energy) and BMD were examined by using linear regression analysis and generalized estimating equations adjusted for confounders. RESULTS: The mean (+/-SD) protein intake at baseline was 15.5 +/- 3.2%. After multivariable adjustment, the mean BMD was similar across each tertile of protein intake. In cross-sectional analyses, low vegetable protein intake was associated with a lower BMD (P = 0.03 for hip, P = 0.10 for spine, and P = 0.04 for whole body). For every percentage increase in the percentage of energy from protein, no significant longitudinal changes in BMD were observed at any anatomic site over the follow-up period. CONCLUSIONS: Data from this longitudinal study suggest that a higher protein intake does not have an adverse effect on bone in premenopausal women. Cross-sectional analyses suggest that low vegetable protein intake is associated with lower BMD.

Characteristics associated with fasting appetite hormones (obestatin, ghrelin, and leptin).

Obestatin, derived from the same gene as the hunger hormone ghrelin, may reduce food intake in animals. The role of obestatin in human physiology is unclear. We evaluated cross-sectional associations between participant characteristics and fasting levels of obestatin as well two other hormones associated with energy balance, ghrelin and leptin. Data are from the baseline visit of the Optimal Macronutrient Intake Trial to Prevent Heart Disease (OMNI-Heart) Trial that enrolled adults with elevated blood pressure (systolic 120-159 mm Hg or a diastolic of 80-99 mm Hg) but who were otherwise healthy. Partial Spearman's correlations and linear regression models estimated the association between age, gender, BMI, physical activity, and smoking with fasting hormones. Obestatin was directly associated with ghrelin (r = 0.45, P < 0.05). On average, overweight (BMI 25-30) and obese (BMI > 30) individuals had obestatin concentrations that were 12.6 (s.d. 8.8) and 25.4 (s.d. 8.4) pg/ml lower compared to normal weight (BMI < 25) individuals, respectively (P for trend = 0.002). Overweight (BMI 25-30) and obese (BMI > 30) individuals had ghrelin concentrations that were 161.7 (s.d. 69.6) and 284.7 (s.d. 66.5) pg/ml lower compared to normal weight (BMI < 25) individuals, respectively (P for trend <0.0001). A 5 unit increase in BMI was associated with 41.3% (s.d. 4.3%) (P < 0.0001) higher leptin. Obestatin and ghrelin are directly correlated and share the same patterns of association with participant characteristics. Modifiable risk factors for chronic diseases, such as BMI, are associated with fasting levels of leptin, obestatin, and ghrelin.