A New Study Reveals One Way Exercise Rewires Your Metabolism
It strengthens muscles, supports heart health, and helps regulate blood sugar. But scientists are continuing to uncover how those benefits happen, and one muscle-derived hormone is getting a lot of attention.
A new systematic review and meta-analysis found that regular exercise significantly increases circulating levels of irisin, a molecule released by muscles during physical activity. The boost in irisin was accompanied by improvements in several key markers of metabolic health in adults with overweight or obesity. Here's what you need to know.
About the study
Researchers analyzed data from 50 randomized controlled trials involving 1,780 adults with overweight or obesity.
The review compared multiple exercise modalities—including aerobic exercise, resistance training, high-intensity interval training (HIIT), and concurrent training (a combination of resistance and aerobic exercise)—against passive control groups.
The primary goal was to determine how exercise affects circulating irisin levels. Irisin is a signaling protein released by skeletal muscle during physical activity. First identified in 2012, it attracted attention quickly because of how broadly it seems to act in the body. Unlike hormones produced by dedicated glands, irisin is made directly by muscle tissue in response to movement, making it a literal product of your workouts.
Researchers also examined several other muscle-derived signaling molecules (called myokines) and common metabolic health markers, including blood sugar, insulin sensitivity, cholesterol, and HbA1c.
Exercise consistently increased irisin
Across all studies, exercise significantly increased circulating irisin compared with no exercise.
Irisin is often referred to as an exercise-induced myokine—a protein released by contracting muscles that helps facilitate communication between muscles and other tissues throughout the body.
Early research suggests irisin may:
- Support healthy glucose metabolism
- Improve insulin sensitivity
- Encourage the conversion of white fat into more metabolically active brown-like fat
- Help regulate energy balance and inflammation
While scientists are still working to fully understand its role, many believe irisin may help explain some of exercise's far-reaching metabolic benefits.
Metabolic health also improved
The rise in irisin wasn't the only encouraging finding.
Compared with inactive control groups, people who exercised also experienced meaningful improvements in several metabolic markers, including:
- Lower fasting blood glucose
- Lower fasting insulin
- Reduced insulin resistance (HOMA-IR)
- Lower HbA1c
- Lower LDL ("bad") cholesterol
- Higher HDL ("good") cholesterol
Exercise also increased two other beneficial myokines (follistatin and FGF-21) both of which are involved in muscle function, energy metabolism, and insulin sensitivity.
Together, these findings reinforce that muscle plays a significant role in metabolism.
Does one type of exercise work best?
Researchers also looked at whether different training styles affected irisin differently.
Resistance training produced the largest increase in irisin levels, followed by HIIT and concurrent training. However, the differences between exercise types were not statistically significant, meaning no one approach clearly outperformed the others.
In other words, nearly every structured exercise program appeared capable of increasing irisin.
That said, resistance training continues to stand out for its many metabolic benefits. Building muscle increases your body's capacity to store glucose, improves insulin sensitivity, supports healthy aging, and helps preserve lean mass during weight loss—all particularly important for people with overweight or obesity.
Why lifting is worth adding to your routine
A few sessions per week of structured resistance work (free weights, machines, bodyweight exercises, or resistance bands) appears to be enough to meaningfully raise irisin and trigger the downstream benefits the meta-analysis identified.
A few things worth keeping in mind:
- Consistency matters more than intensity: The meta-analysis looked at chronic training adaptations, not single-session spikes. Regular, sustained resistance training over weeks and months is what drives meaningful changes in circulating irisin.
- All movement counts: HIIT and combined training also raised irisin significantly. If resistance training isn't your preference, pairing aerobic work with some resistance-based movement is a strong alternative.
- Muscle is the organ doing the work: The more muscle you have and the more you challenge it, the stronger the irisin signal. This is one more reason why building and maintaining muscle becomes increasingly important as you age.
- The benefits compound: Irisin doesn't work in isolation. The improvements in blood sugar, insulin sensitivity, cholesterol, follistatin, and FGF-21 seen in this meta-analysis reflect a whole-body hormonal response to consistent training.
The takeaway
Regular physical activity appears to increase irisin, while also improving blood sugar regulation, insulin sensitivity, and cholesterol levels. And every workout prompts your muscles to act as an endocrine organ, releasing compounds that help support whole-body metabolic health.