According to Gram Research analysis, certain gut bacteria and blood proteins can predict how much someone’s heart and lung fitness will improve from intense exercise. A 2026 study of 35 men with prediabetes found that those with higher baseline levels of beneficial bacteria like Prevotella showed the largest fitness gains after 12 weeks of training, while those with higher erythropoietin hormone levels showed smaller improvements.
A new study looked at 35 men with prediabetes who did intense interval training for 12 weeks. Researchers discovered that certain gut bacteria and blood proteins can predict who will improve their heart and lung fitness the most. By measuring these biological markers before exercise started, scientists could identify which people would respond best to training. This finding could help doctors create personalized exercise plans tailored to each person’s body chemistry, making fitness improvements more predictable and effective for people at risk of diabetes.
Key Statistics
A 2026 study of 35 men with prediabetes found that after 12 weeks of high-intensity interval training, average heart and lung fitness improved by 0.47 liters of oxygen per minute, with individual responses ranging from zero to 1.7 liters per minute.
According to research reviewed by Gram, people with higher baseline levels of the gut bacterium Prevotella showed significantly larger fitness improvements from exercise, with each unit increase in Prevotella associated with 105 units of additional fitness gain.
A 2026 research article found that including blood protein measurements in fitness prediction models increased the ability to explain fitness improvements from 27% to 37%, showing that biological markers add important information beyond traditional health measurements.
The study revealed that people with higher baseline erythropoietin (EPO) hormone levels showed smaller fitness improvements from 12 weeks of intense interval training, suggesting this hormone may limit exercise response in people with prediabetes.
The Quick Take
- What they studied: Whether certain bacteria in the gut and proteins in the blood can predict how much someone’s heart and lung fitness will improve from intense interval training.
- Who participated: 35 Chinese men aged 24-62 years old who were overweight or obese and had prediabetes (early warning signs of diabetes). None were taking diabetes medications at the start.
- Key finding: People with more of certain gut bacteria called Prevotella, Coprococcus, and Hungatella at the start showed the biggest improvements in fitness. Those with higher levels of a hormone called erythropoietin (EPO) showed smaller improvements.
- What it means for you: A simple blood and stool test before starting exercise might predict how much your fitness will improve, helping doctors create better personalized training plans. However, this is early research with a small group, so more studies are needed before doctors use this in practice.
The Research Details
Researchers recruited 35 men with prediabetes and had them do high-intensity interval training (HIIT) for 12 weeks. HIIT means alternating between very hard exercise and easier recovery periods. Before and after the training, scientists collected blood samples and stool samples to measure three different things: proteins in the blood, bacteria in the gut, and small molecules called metabolites.
The researchers used advanced laboratory techniques to identify hundreds of different proteins and thousands of different bacterial species. They then looked at which of these biological markers were connected to how much each person’s heart and lung fitness improved. Heart and lung fitness was measured by how much oxygen someone could use during maximum exercise (called VO₂peak).
This approach is called “multi-omics,” which means looking at many different biological systems at once rather than just one. The scientists used statistical methods to find which markers were most strongly connected to fitness improvements.
Understanding why some people respond better to exercise than others is important because it’s frustrating when people work hard but don’t see results. If doctors can predict who will benefit most from exercise using simple tests, they can create better training plans and help people stay motivated. This is especially important for people with prediabetes, who need to improve their fitness to prevent developing type 2 diabetes.
This study has some strengths: it measured multiple biological systems at once, used advanced laboratory techniques, and collected samples both before and after exercise. However, there are important limitations: the sample size is small (only 35 people), all participants were men from one country, and the study didn’t have a control group that didn’t exercise. The results need to be confirmed in larger, more diverse groups before doctors can use these tests in real practice.
What the Results Show
After 12 weeks of intense interval training, the average person’s heart and lung fitness improved by 0.47 liters of oxygen per minute. However, there was huge variation—some people improved by almost 1.7 liters per minute while others didn’t improve at all. This variation is the key puzzle the researchers were trying to solve.
The biggest discovery was about gut bacteria. People who started with higher amounts of three specific types of bacteria—Prevotella, Coprococcus, and Hungatella—showed the biggest fitness improvements. These bacteria are important because they produce short-chain fatty acids, which are beneficial compounds that help the body work better. The connection was strong: for every unit increase in Prevotella bacteria, fitness improvement increased by about 105 units.
The study also found that a hormone called erythropoietin (EPO) worked the opposite way. People with higher EPO levels at the start showed smaller fitness improvements. Additionally, when growth hormone increased during exercise, people improved more. But when another protein called BACH1 increased during exercise, people improved less.
The researchers found that lean muscle mass was the strongest predictor of fitness improvement among traditional health measurements. People with more muscle improved more than people with less muscle. When scientists added the blood protein measurements to their prediction model, they could explain 37% of why people improved differently—compared to only 27% when using traditional measurements alone. This shows that the new biological markers add important information that doctors don’t currently use.
Previous research has shown that people respond very differently to the same exercise program, but scientists didn’t fully understand why. This study is one of the first to look at so many different biological systems at once to explain these differences. Earlier studies focused on single factors like genetics or fitness level, but this research shows that gut bacteria, blood proteins, and muscle mass all work together to determine fitness improvements.
The study is small with only 35 participants, all men from China, so results may not apply to women or people from other backgrounds. Without a control group that didn’t exercise, we can’t be completely sure the changes were caused by exercise rather than other factors. Some of the statistical connections found were weak and might have happened by chance. The study was done over only 12 weeks, so we don’t know if these patterns hold true for longer exercise programs. Finally, the biological markers that predicted improvement need to be tested in a new group of people to confirm the findings are real.
The Bottom Line
If you have prediabetes, doing high-intensity interval training for 12 weeks can improve your heart and lung fitness. The average improvement was meaningful and could help prevent diabetes. However, don’t expect the same results as someone else—your body’s response depends on factors like your gut bacteria and muscle mass. Talk to your doctor before starting any new exercise program, especially if you have prediabetes. (Confidence: Moderate—this is based on a small study that needs confirmation in larger groups.)
This research is most relevant for people with prediabetes who want to improve their fitness through exercise. It’s also important for doctors and fitness professionals who work with people at risk of diabetes. The findings don’t yet apply to people without prediabetes or to women, since the study only included men with prediabetes.
In this study, people saw fitness improvements after 12 weeks of consistent high-intensity interval training. Most improvements likely happened gradually over those 12 weeks rather than all at once. You should expect to need at least 8-12 weeks of regular training to see meaningful changes in your heart and lung fitness.
Frequently Asked Questions
Can a blood test predict how much my fitness will improve from exercise?
Research suggests certain blood proteins and gut bacteria may predict fitness improvements, but this is still early research. A 2026 study found that erythropoietin levels and specific bacteria could forecast who would benefit most from 12 weeks of training, though these tests aren’t yet available in regular medical practice.
What gut bacteria help you get fit faster?
Three types of bacteria—Prevotella, Coprococcus, and Hungatella—were associated with larger fitness improvements in a 2026 study of 35 men with prediabetes. These bacteria produce short-chain fatty acids, which support overall body health and may enhance exercise response.
How much can high-intensity interval training improve my heart and lung fitness?
In a 2026 study, people with prediabetes improved their heart and lung fitness by an average of 0.47 liters of oxygen per minute after 12 weeks of HIIT, though individual results varied widely from zero to 1.7 liters per minute depending on their starting biology.
Does muscle mass affect how much you improve from exercise?
Yes, a 2026 study found that lean muscle mass was the strongest predictor of fitness improvement from exercise. People with more muscle at the start showed larger gains in heart and lung fitness compared to those with less muscle.
How long does it take to see fitness improvements from HIIT training?
The 2026 study measured improvements after 12 weeks of consistent high-intensity interval training. Most people should expect to need at least 8-12 weeks of regular training to see meaningful changes in heart and lung fitness.
Want to Apply This Research?
- Track your weekly high-intensity interval training sessions and measure your fitness progress every 4 weeks using a simple test like how long you can exercise at maximum effort or how you feel during intense activity. Note any changes in energy levels and recovery time between workouts.
- Start with 2-3 sessions per week of high-intensity interval training, alternating 30-60 seconds of very hard exercise with 1-2 minutes of easier recovery. Log each session in the app and track how your fitness improves over 12 weeks. Also log your diet, especially foods that support healthy gut bacteria like fiber-rich vegetables and whole grains.
- Create a 12-week fitness challenge in the app where you track HIIT workouts, measure fitness improvements monthly, and monitor how you feel during and after exercise. Connect this to dietary tracking to see if certain foods correlate with better workout performance and recovery.
This research is preliminary and based on a small study of 35 men with prediabetes. The biological markers discussed are not yet available for clinical use in predicting individual exercise response. Before starting any new exercise program, especially if you have prediabetes, diabetes, or other health conditions, consult with your healthcare provider. This article is for educational purposes and should not replace professional medical advice. Individual fitness improvements vary widely based on many factors including genetics, diet, sleep, and consistency with training.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.