Exercise Intensity and Hunger Hormones, Implications for Training

How Exercise Intensity and Gender Influence Appetite and Ghrelin Hormones

Research has shown that exercise impacts appetite-regulating hormones, yet the role of exercise intensity and gender on ghrelin levels—notably its acylated (AG) and deacylated (DAG) forms—remains complex. A recent study provides new insights, revealing that high-intensity exercise and sex differences can significantly influence these hormones and perception of hunger.

Key Findings on Exercise Intensity and Ghrelin Levels

The study found that high-intensity exercise effectively reduced all forms of ghrelin (TG, AG, and DAG) in both men and women, while moderate-intensity exercise often had minimal effect or even increased ghrelin levels. This reinforces that surpassing the lactate threshold—a marker used to determine high-intensity exercise—may be necessary for suppressing ghrelin. Lactate's role here appears linked to its activation of stomach receptors that inhibit ghrelin release, though it isn’t the sole driver of ghrelin reduction.

Interestingly, the study noted that although men and women experienced reduced DAG after high-intensity exercise, only women had significantly lower AG levels. This aligns with other research suggesting that women, likely due to hormonal and body composition differences, exhibit distinct ghrelin dynamics compared to men.

How Ghrelin Affects Appetite Perception

Ghrelin is known to rise and fall with hunger cycles, spiking before meals and dropping afterwards. In this study, hunger scores were higher following moderate-intensity exercise compared to no exercise, suggesting that moderate-intensity might stimulate appetite. High-intensity exercise, however, appeared to blunt this effect, possibly due to the reduction in ghrelin isoforms. The study found stronger correlations between ghrelin levels and hunger than with overall appetite, with AG specifically linked to hunger-related hypothalamic activity.

Sex Differences in Ghrelin Response

Baseline levels of total ghrelin and DAG were higher in females, which may reflect underlying hormonal influences such as estrogen. Females also showed greater sensitivity to high-intensity exercise’s effects on ghrelin, which could hint at sex-specific pathways affecting ghrelin release and degradation. This may have implications for how exercise intensity could be optimised differently for men and women.

Limitations of the Study

While these findings are promising, the study faced limitations. The small sample size, particularly among females, may limit the power to assess sex differences robustly. Additionally, participants fasted before each session, which doesn’t fully replicate real-world conditions where people eat before or after exercise. The study also did not examine other appetite-regulating factors like polypeptide YY and glucagon-like peptide-1, which might further influence hunger perceptions. Furthermore, as only lean participants were studied, these results may not apply to those who are overweight or obese, where ghrelin behaviour can differ.

Implications for Exercise and Appetite Management

The findings suggest that high-intensity workouts might be particularly effective for managing hunger and ghrelin levels, especially in women. While these results are insightful, they highlight the need for more research into sex-specific responses, as well as the effects in individuals with different body compositions. Future studies could help refine exercise prescriptions, potentially offering tailored strategies to aid in weight management and appetite control.

Want to read more?

The complete study, authored by Dr. Kara Anderson, affiliated with the University of Virginia and the University of Virginia Health System. was published in the Journal of the Endocrine Society and is available Here.