How Diet and Exercise Change Your Hunger and Fullness Hormones When You're Obese | Research

The takeaway

A 12-week diet and exercise program reduced the hunger hormone ghrelin and increased the satiety hormone PYY in obese individuals, but their GLP-1 and PYY levels still didn't reach those of healthy-weight people.

Still below normal after 12 weeks
Even after diet and exercise significantly improved appetite hormone levels, obese participants' GLP-1 and PYY still didn't reach healthy-weight control levels

What the researchers found

After 12 weeks of combined diet (1,000–1,500 kcal/day) and exercise (at least 5,000 steps/day), obese individuals showed significant changes in appetite-regulating peptide hormones: ghrelin (the hunger hormone) decreased significantly, while PYY (a satiety hormone) increased significantly. These shifts support better appetite control and weight maintenance.

However, even after the intervention, the obese group's GLP-1 and PYY levels still did not reach the levels seen in healthy-weight controls. This suggests that while diet and exercise improve appetite hormone signaling, they may not fully normalize the peptide imbalances associated with obesity.

Why it matters

Understanding how diet and exercise affect appetite peptides helps explain why these interventions work — and why they sometimes aren't enough. The finding that GLP-1 and PYY didn't normalize even after treatment provides biological context for why many people struggle to maintain weight loss, and why GLP-1 agonist drugs like semaglutide have become so popular: they may compensate for a deficit that lifestyle changes alone can't fully correct.

The numbers in context

n=62 obese participants + 48 healthy controls · 12-week intervention · 1,000–1,500 kcal/day diet · ≥5,000 steps/day exercise · BMI ≥30 for case group

How the study worked

Researchers enrolled 62 obese individuals (BMI ≥30) and 48 healthy-weight controls. The obese group followed a 12-week program combining a calorie-restricted diet (1,000–1,500 kcal/day, tailored to age, gender, and BMI) with daily exercise (at least 5,000 steps/day). Blood samples were taken before and after the 12-week period, and ghrelin, GLP-1, and PYY levels were measured using ELISA assays.

Who was studied

62 obese adults (BMI ≥30) and 48 healthy-weight controls

What this study cannot tell us

The study used a relatively modest exercise target (5,000 steps/day, which is below most health recommendations). The abstract doesn't report the actual amount of weight lost, making it harder to connect the hormone changes to specific outcomes. There was no randomization or blinding described, and the control group didn't undergo the intervention, limiting causal conclusions. The ELISA methodology may also be less precise than newer assay techniques.

How to read the evidence

This is a controlled clinical study with pre- and post-intervention measurements and a healthy comparison group. However, it lacks randomization, blinding, and detailed weight loss data. The sample size of 110 is moderate, and the study design limits causal inference.

When this study was published

Published in 2024, this is a recent study that adds current data to the ongoing investigation of how lifestyle interventions affect appetite peptide hormones in obesity.

The bigger picture

This study adds to growing evidence that obesity involves a fundamental disruption of appetite-regulating peptide signaling — not just a lack of willpower. The persistent gap between obese and healthy-weight hormone levels, even after successful intervention, helps explain the biological basis for weight regain and provides context for why pharmacological GLP-1 agonists have proven so effective: they may be correcting a peptide deficit that the body struggles to fix on its own.

Questions still open

Would a more intensive or longer exercise program eventually normalize GLP-1 and PYY levels to match healthy-weight individuals?
Do the appetite hormone improvements persist after the structured program ends, or do they revert as weight regain occurs?
How do these natural peptide changes from diet and exercise compare to the effects of GLP-1 agonist medications?

Common questions

Does diet and exercise actually change your hunger hormones?

Yes. This study found that 12 weeks of calorie restriction and daily walking significantly reduced ghrelin (the hormone that makes you hungry) and increased PYY (a hormone that makes you feel full). These changes support better appetite control and help explain why structured diet and exercise programs can be effective for weight management.

If diet and exercise help, why do people still struggle with weight after trying?

Even though the hormones improved, they didn't fully normalize — obese participants' GLP-1 and PYY levels remained lower than healthy-weight people's even after 12 weeks of effort. This biological gap may explain persistent hunger and cravings, and it's one reason researchers believe peptide-based drugs like GLP-1 agonists can be a valuable addition to lifestyle changes.

Read the original research

Changes in ghrelin, GLP-1, and PYY levels after diet and exercise in obese individuals.

Revista da Associacao Medica Brasileira (1992), 70(1), e20230263

View on PubMed ↗Publisher’s paper ↗

Citation

Alyar, Gülşah; Umudum, Fatma Zuhal; Akbaş, Nergis. (2024). Changes in ghrelin, GLP-1, and PYY levels after diet and exercise in obese individuals.. Revista da Associacao Medica Brasileira (1992), 70(1), e20230263. https://doi.org/10.1590/1806-9282.20230263