Does Metformin Block the Benefits of Exercise? What the New Rutgers Study Really Shows

If you have ever stepped off a treadmill expecting your blood sugar to drop, only to find the number stubbornly unchanged, the latest research out of Rutgers may explain why.

A new clinical trial published in The Journal of Clinical Endocrinology & Metabolism suggests that metformin, the world’s most prescribed diabetes drug, may actually dull some of the cardiovascular and metabolic gains you would normally expect from a structured exercise program.

This is a significant finding because metformin and exercise have been considered complementary cornerstones of type 2 diabetes care for nearly two decades. The assumption has been that pairing them produces additive benefits. The new data complicates that picture, showing that the combination may not always deliver what doctors and patients have come to expect.

The question of whether metformin blocks exercise benefits is now front and center for millions of Americans living with prediabetes, metabolic syndrome, or type 2 diabetes. To understand what this research really means, it helps to look at what the trial actually found, why the interaction may occur, and what experts are recommending right now. This article walks through the findings, the limitations, and the practical takeaways without overstating any single result.

Why Metformin and Exercise Are Often Used Together

Metformin and exercise have long been the dual foundation of type 2 diabetes management. Each addresses the disease through different but complementary pathways, which is precisely why clinicians have historically prescribed them together.

Physical activity increases the muscle’s ability to absorb glucose from the bloodstream, both during the workout and for hours afterward. Aerobic exercise, resistance training, and high-intensity interval work all improve insulin sensitivity through multiple mechanisms, including better blood vessel function, mitochondrial adaptation, and reduced inflammation.

For someone with prediabetes or early type 2 diabetes, regular exercise can cut the risk of progression to full type 2 diabetes by more than half, according to research from the Diabetes Prevention Program. That is a stronger effect than most medications produce.

Metformin works differently. It reduces glucose production in the liver, increases insulin sensitivity in peripheral tissues, and slows glucose absorption in the gut. It has been the first-line oral therapy for type 2 diabetes since the early 2000s and is now taken by more than 20 million Americans.

Since 2006, U.S. clinical guidelines have advised patients with elevated blood sugar to combine metformin with regular physical activity. The logic was straightforward: two effective therapies should produce stronger results when used together.

As Dr. Steven Malin, professor of kinesiology and health at Rutgers University, explained in a Rutgers news release, most providers assume “one plus one equals two” when it comes to layering these therapies. But emerging evidence is challenging that math.

What the New Rutgers Study Found

Dr. Malin and his team set out to test this assumption directly, using a more rigorous design than earlier studies on the topic.

The researchers recruited 72 adults at elevated risk for metabolic syndrome, a cluster of conditions that includes high blood pressure, abdominal obesity, elevated blood sugar, and abnormal lipid levels. Participants were randomized into four groups for a 16-week trial: high-intensity exercise plus placebo, high-intensity exercise plus metformin, low-intensity exercise plus placebo, and low-intensity exercise plus metformin.

After 16 weeks, the placebo groups showed the expected improvements. Their blood vessels became more responsive to insulin, their aerobic fitness increased, and their glucose control improved.

The metformin groups told a different story. Across both intensity levels, the addition of metformin substantially reduced these gains. The researchers documented this in their published findings on vascular insulin sensitivity after exercise training.

The study found that the Rutgers metformin exercise data showed reduced gains in vascular insulin sensitivity at both the level of larger arteries and small capillaries. This matters because insulin-stimulated blood flow is one of the key mechanisms your body uses to deliver nutrients and clear glucose from the bloodstream after meals.

Read More: Insulin Sensitivity vs. Insulin Resistance?

Possible Reasons Metformin May Blunt Exercise Benefits

The study did not just document the blunting effect. It also offered clues about why it might be happening at the cellular level.

Metformin works partly by inhibiting Complex I of the mitochondrial electron transport chain. This reduces oxidative stress and contributes to its glucose-lowering effects. But that same mechanism may interfere with mitochondria’s ability to adapt to exercise training.

Dr. Adam Konopka, assistant professor in the Division of Geriatrics and Gerontology at the University of Wisconsin–Madison, has documented this interaction in his own research.

In a landmark 2018 paper published in Aging Cell on metformin and aerobic exercise training in older adults, Konopka and colleagues reported that metformin attenuated improvements in cardiorespiratory fitness and whole-body insulin sensitivity, with the change in insulin sensitivity correlated to changes in mitochondrial respiration.

Healthy mitochondria are central to how the body responds to repeated exercise stress. When mitochondrial function is suppressed, the cellular machinery that normally drives fitness improvements may not respond as strongly.

The Rutgers trial extended this work into the vascular system. By showing that metformin can blunt insulin’s effects on both large arteries and tiny capillaries, the researchers added a new dimension to the debate over metformin and exercise benefits. The drug appears to interfere not just with muscle adaptations but with how the cardiovascular system responds to training.

Does This Mean Exercise Doesn’t Work if You Take Metformin?

This is the question that matters most to patients, and the answer is more reassuring than the headlines suggest.

Even with the blunting effect, exercise continues to deliver real benefits for people taking metformin. The placebo and metformin groups in the Rutgers study both showed improvements in some markers. The difference was the size of the gains, not their absence.

Cardiovascular fitness, mood, sleep quality, body composition, and bone health all improve with regular movement, regardless of whether someone takes metformin. Many of these benefits operate through pathways unaffected by the drug.

Not everyone responds to metformin in the same way. Some people in the Konopka study responded positively to the metformin-plus-exercise combination, while others responded negatively. This variability suggests that genetics, baseline fitness, and metabolic context all play a role in how someone reacts.

Who Might Be Most Affected

The blunting effect appears to matter more for some groups than others, and understanding which patients fall into the higher-impact category helps shape clinical decisions.

People with prediabetes or metabolic syndrome who are using exercise specifically to improve insulin sensitivity may see smaller gains than expected when metformin is added. Older adults starting new aerobic programs may also experience reduced improvements in VO2 max and mitochondrial function. Individuals whose primary goal is to improve vascular insulin sensitivity should know that this specific benefit appears to be most affected by the drug.

For people with established type 2 diabetes who rely on metformin for glycemic control, the calculus is different. The drug’s blood sugar-lowering effects are well documented and clinically meaningful, even if some exercise gains are reduced.

What This Means for Blood Sugar Control

The metformin vs. exercise question in diabetes is not really an either-or situation. Each tool addresses glucose control through different routes, and most patients will continue to benefit from both.

A single bout of moderate-intensity exercise can lower blood glucose for hours afterward. Regular training reduces HbA1c, improves fasting glucose levels, and lowers the risk of cardiovascular disease. These effects are independent of medication.

Metformin reduces hepatic glucose production and improves insulin sensitivity through pathways that exercise alone cannot replicate. It has been associated with reduced cardiovascular mortality and may have additional benefits in cancer prevention and aging that are still being investigated.

For most patients, the combination remains beneficial. The new research suggests the gains may be smaller than previously assumed, but smaller is not zero. The takeaway is to set realistic expectations rather than abandon either treatment.

Read More: Low-Carb vs. Low-Fat for Type 2 Diabetes: What 27 Clinical Trials Actually Found

Limitations of the Study

Like any clinical trial, the Rutgers study has constraints that should temper how strongly its findings are interpreted.

Seventy-two participants are a reasonable number for an intensive 16-week intervention, but it limits the power to detect smaller effects or differences across subgroups. Larger trials are needed to confirm the magnitude of the blunting effect.

Participants were adults at risk for metabolic syndrome, which is a relatively narrow slice of the broader diabetes population. The findings may not translate directly to people with established type 2 diabetes, those on multiple medications, or younger adults using metformin off-label.

Sixteen weeks captures the early adaptation phase but does not show what happens over the years of combined treatment. Some effects may diminish or change with longer use.

Researchers studying the interaction between metformin and cardiovascular fitness agree that more rigorous, long-term studies are needed.

Dr. Brendan Gabriel, a principal investigator at the University of Aberdeen who has published extensively on this topic, has noted in his team’s research on the interaction between morning exercise and pre-breakfast metformin that timing and dosing strategies may significantly affect outcomes, suggesting the picture is more nuanced than a simple “metformin blunts exercise” framing.

What Experts Recommend Right Now

The most consistent message from researchers and clinicians is this: do not stop your medication based on a single study, and do not stop exercising either.

Metformin remains the first-line oral therapy for type 2 diabetes. Its glucose-lowering effects, cardiovascular safety profile, and low cost make it one of the most valuable tools in diabetes care. Discontinuing it without medical guidance can lead to rapid deterioration in blood sugar control.

Exercise is not optional. Even if some specific benefits are reduced, the overall return on physical activity for cardiometabolic health remains strong.

Dr. Disha Narang, an endocrinologist and Director of Obesity Medicine at Endeavor Health in Chicago, emphasizes that medication decisions should be individualized. As she explained in a published interview about metformin’s broader effects, the drug may have anti-inflammatory properties that benefit cardiovascular health and other systems, suggesting the full picture extends beyond exercise response alone.

Some research suggests the timing of metformin doses relative to exercise sessions may influence outcomes, although this remains an active area of study.

Practical Tips if You Take Metformin and Exercise

For patients trying to make sense of this research, a few evidence-based practices can help maximize what exercise still offers.

Focus on consistency rather than intensity alone. Both high and low-intensity exercise showed blunting effects in the Rutgers trial, so chasing higher intensity is not the solution. Consistent, sustainable activity produces benefits over time.

Include resistance training. Strength work supports muscle mass, which is the primary site of glucose disposal in the body. More muscle generally means better glucose handling, regardless of medication.

Monitor blood sugar response. A continuous glucose monitor or regular finger-stick checks can show how your body specifically responds to different types and timings of exercise.

Track energy and recovery. Some patients on metformin report that workouts feel harder or that recovery takes longer. Paying attention to these signals can help you adjust intensity and frequency appropriately.

Read More: American Diabetes Month 2025: Simple Steps to Lower Your Risk

When to Talk to a Healthcare Professional

There are specific situations in which the new research should prompt a conversation with your provider rather than a unilateral change to your routine.

If you have been exercising consistently and your blood sugar or fitness markers are not improving as expected, it may be worth discussing whether adjusting the timing or dose of metformin could help. Questions about how to schedule your dose around workouts deserve a clinician’s input rather than online speculation.

Persistent fatigue, exercise intolerance, or unusually slow recovery can also be signs that warrant a medical conversation. And anyone considering metformin off-label for anti-aging, weight loss, or other unproven uses should weigh the potential reduction in exercise gains against the speculative benefits.

Read More: The 11 Push-Up Challenge: Benefits, How It Works, and How to Do It Safely

Practical Takeaway: More Research Is Needed

The early evidence is consistent enough to take seriously. Metformin appears to dampen some of the cardiovascular and metabolic improvements that would normally come from regular exercise, particularly in vascular insulin sensitivity, aerobic fitness, and glucose control.

Both Rutgers and the Konopka group at Wisconsin have now produced studies pointing in the same direction, and the proposed mechanism, mitochondrial inhibition, fits the broader pharmacology of the drug.

What the evidence does not support is alarmism. Exercise still works for people on metformin. Metformin still lowers blood sugar effectively. The combined approach still benefits most patients more than either tool alone, even if the gains are not perfectly additive. The clinical reality is that diabetes care is built on layered interventions, and a single trial showing diminishing returns does not overturn decades of evidence supporting both treatments.

This study opens the door to more personalized care. Future research will likely explore whether specific exercise timing, dose adjustments, or alternative medications can preserve more of the exercise benefit.

In the meantime, the best move is to keep moving, keep taking medication as prescribed, and keep the conversation going with your healthcare team. The science is evolving, but the fundamentals of metabolic health have not changed.

FAQs

Does metformin completely cancel out the benefits of exercise?

No. The Rutgers study found that metformin blunted some specific gains, particularly in vascular insulin sensitivity and aerobic fitness, but exercise still produced measurable benefits in the metformin groups. Exercise remains valuable for blood sugar control, weight management, mood, and cardiovascular health, regardless of medication use.

Should I stop taking metformin so my workouts work better?

No. Stopping metformin without medical guidance can lead to rapid worsening of blood sugar control. The drug’s benefits on glycemic control and cardiovascular outcomes are well established. Any changes to your medication should be discussed with your healthcare provider.

Can you exercise while taking metformin safely?

Yes. Metformin does not prevent safe exercise, and physical activity is still strongly recommended for people with type 2 diabetes. Some patients report that workouts feel harder while on the drug, but this is generally manageable with appropriate pacing.