Jennifer Warner, WebMD Medical News, Sep. 14
Black women may be more prone to obesity than white women because they are naturally hungrier, a new study shows.
Researchers found black women had significantly higher levels of the hunger hormone ghrelin after eating than white women — regardless of their weight, calorie intake, or age.
Ghrelin is a hormone released primarily in the stomach, which is thought to trigger hunger. Ghrelin levels increase dramatically before a meal and then are suppressed for about three hours after eating a meal.
Obesity is a growing epidemic in the U.S., but researchers say African Americans are 1.6 times more likely to be obese than whites. Statistics show that 31% of African Americans are obese compared with 20% of whites.
As a result, researchers say black women suffer from higher rates of obesity-related illnesses, such as diabetes and high blood pressure, than white women.
Hunger Hormone May Vary by Race
In this study, published in the September issue of the Journal of Clinical Endocrinology & Metabolism, researchers looked at whether differences in ghrelin levels after meals might be related to the racial differences seen in obesity rates.
Forty-three women, 22 white and 21 black, followed a controlled diet for four days, and then blood samples were taken two hours after eating identical meals.
Researchers tested the blood for ghrelin and leptin (another hormone linked to obesity) as well as measured 24-hour cortisol levels using urine tests. Elevated cortisol levels are common among obese persons and in those with poorly controlled diabetes; they increase the risk of heart disease.
The study showed that ghrelin levels after the meal were significantly higher among black women versus white women, even after they controlled for the women’s body mass index (BMI, a measure of weight in relation to height used to indicate obesity). Ghrelin levels are inversely related to body weight.
Even after adjusting for factors that might alter the level of ghrelin, obese black women had the highest average ghrelin and leptin levels overall.
In addition, higher ghrelin levels were associated with higher cortisol levels in black women but not in white women.
“These findings suggest subnormal [post-meal] ghrelin expression (or faster ghrelin rebound) in black women, especially the obese, that might play a role in their increased prevalence of obesity and cardiovascular disorders,” write researcher Kimberly Brownley, PhD, of the University of North Carolina, and colleagues.
Surprisingly, researchers say they also failed to find the normal inverse relationship between ghrelin levels and obesity. Previous reports showed that ghrelin concentrations declined with rising BMI. But in this study ghrelin levels were not significantly lower in obese compared with nonobese women.
Instead, lower ghrelin levels were associated with greater fat around the midsection in white women, but no such relationship was found in black women.