African Americans had lower levels of appetite-suppressing peptide PYY and hunger hormone ghrelin compared to Whites, but despite these hormonal differences, no racial differences in actual food intake or appetite were observed.
Hormones differ, behavior doesn'tAfrican Americans had significantly different levels of appetite peptides (PYY, ghrelin, leptin) compared to Whites, but these hormonal differences produced no measurable differences in appetite or food intake.
What the researchers found
At baseline, African Americans had significantly lower peptide YY (PYY; p<0.05), lower ghrelin (p=0.02), and higher leptin (p<0.05) compared to Whites. Despite these hormonal differences, no racial differences were observed in actual food intake at laboratory-controlled meals.
In the exercise intervention, leptin increased in African Americans in the 8 KKW exercise group compared to Whites (p=0.01), but no other race-by-group interactions were evident for appetite hormones, appetite ratings, or food intake. The disconnect between hormonal differences and behavioral outcomes suggests that appetite regulation in the context of obesity is more complex than hormone levels alone.
Why it matters
Understanding the biological basis of racial obesity disparities is important for developing targeted interventions. This study reveals that while appetite-regulating peptide hormones differ between racial groups, these differences don't directly translate to differences in eating behavior — suggesting that social, environmental, and other biological factors are likely more important drivers of obesity disparities than appetite hormone levels alone.
How the study worked
This was a secondary analysis of the E-MECHANIC randomized clinical trial. 164 overweight/obese adults (53 African Americans, 111 Whites) were randomized to a control group or supervised exercise groups at 8 or 20 KKW. Participants consumed standardized lunch and dinner at baseline and follow-up, with appetite ratings and blood hormone levels (PYY, ghrelin, leptin) measured before and after meals. Leptin was measured in fasting samples only.
What this study cannot tell us
The sample was predominantly from one geographic area (Pennington Biomedical, Louisiana), limiting generalizability. African Americans were underrepresented (53 vs. 111 Whites). Laboratory-based meals may not reflect real-world eating patterns. The study measured a limited set of appetite hormones and did not assess other important mediators like GLP-1 or CCK. Socioeconomic factors, dietary habits, and cultural food preferences were not fully controlled. The exercise intervention was relatively short-term.
How to read the evidence
This is a secondary analysis of a well-designed randomized clinical trial (E-MECHANIC) with objective laboratory-based measurements. The evidence is moderate quality, limited by the smaller African American subgroup and the inability to control for all potential confounders.
When this study was published
Published in 2019, this study addresses an ongoing and important question about biological contributors to racial health disparities in obesity.
The bigger picture
Appetite-regulating peptides like PYY, ghrelin, and leptin are central to understanding obesity biology. This study adds nuance by showing that population-level differences in these hormones don't necessarily predict eating behavior, challenging simplistic hormone-driven models of obesity. The findings support a more complex, multi-factorial understanding of weight regulation that includes hormonal, behavioral, environmental, and socioeconomic factors.
Questions still open
- If appetite hormones don't explain racial obesity disparities, what are the primary biological or environmental drivers?
- Do differences in GLP-1 or other incretin peptides contribute to racial variations in weight regulation?
- Would longer or more intensive exercise interventions reveal larger racial differences in appetite hormone responses?
Common questions
Do appetite hormones explain why some racial groups have higher obesity rates?
What are PYY and ghrelin and why do they matter for weight?
Read the original research
Racial Variations in Appetite-Related Hormones, Appetite, and Laboratory-Based Energy Intake from the E-MECHANIC Randomized Clinical Trial.
Nutrients, 11(9)
Citation
Dorling, James L; Church, Timothy S; Myers, Candice A; Höchsmann, Christoph; White, Ursula A; Hsia, Daniel S; Martin, Corby K; Apolzan, John W. (2019). Racial Variations in Appetite-Related Hormones, Appetite, and Laboratory-Based Energy Intake from the E-MECHANIC Randomized Clinical Trial.. Nutrients, 11(9). https://doi.org/10.3390/nu11092018