Relationship of ghrelin and leptin hormones with body mass index and waist circumference in a random sample of adults

Objective To evaluate the relationship of ghrelin and leptin hormones with body mass index (BMI) and waist circumference in a population-based random sample of adult men and women subsequently categorized from normal weight to severely obese based on BMI criteria. The relationship between total ghrelin and leptin was also evaluated. Design A cross-sectional study was conducted on adults. Methods Two-hundred thirty-three men (n=107) and women (n = 126) between the ages of 23 and 75 years were randomly selected from a database of over 600,000 adults who had previously participated in a population-based study conducted by the University of Utah Cardiovascular Genetics Program. Items collected included height, weight, waist circumference, and fasting blood samples. Blood samples were later thawed, and plasma leptin and total ghrelin levels were analyzed with radioimmunoassay kits. Results Leptin levels were directly associated with BMI (r=0.72, P=0.001) and waist circumference (r=0.71, P=0.0001), whereas total ghrelin was inversely associated with BMI (r=-0.39, P=0.001) and waist circumference (r=-0.37, P=0.001). There were also statistically significant linear changes in means across the BMI categories for both hormones. After controlling for BMI and waist circumference, the highly significant correlation of leptin with ghrelin (r=-0.39) was reduced but still significant (r=-0.17, P=0.01). Conclusion Leptin increases and ghrelin decreases were linear over the five BMI categories, suggesting there is no threshold of BMI where the hormone levels change abruptly. There remain other factors beyond current BMI and waist circumference that induce a correlation of these two hormones. Further understanding of the role that each of these hormones has in influencing appetite and body weight may provide insight into mechanisms involved with obesity.