Metformin and exercise

If you like concrete answers and absolutes, longevity is not a fun sandbox to play in.

Read Time 3 minutes

If you like concrete answers and absolutes, longevity is not a fun sandbox to play in. There are surprisingly few things that researchers can agree on when it comes to improving healthspan and lifespan in relatively healthy individuals. However, exercise is generally accepted as one of the few tools that can reliably extend healthspan. (Biting my tongue on a rant of what the definition of “exercise” really is…)

Relatively intense physical exercise is inversely associated with immobility, several cancers, cardiovascular disease, and premature mortality. The proxies for exercise’s benefits we typically see in the literature are improved insulin sensitivity, increased skeletal muscle size, and increased cardiorespiratory fitness, or CRF for short.

So, when an article comes out in the New York Times saying there’s a drug out there that may blunt the health benefits of exercise in healthy older adults, it probably gives one pause. When that drug turns out to be metformin, a candidate for extending healthspan (and is often used off-label for this purpose), it probably gives one a WTF? moment.

If you ask researchers in the longevity field what are the most intriguing interventions for slowing aging and/or increasing healthspan, aside from nutritional manipulation and rapamycin (and aforementioned exercise), a common answer is the chronic use of metformin. So, it’s probably not unreasonable to assume that combining metformin and exercise may produce better results than employing either approach alone. However, a 2019 study casts doubts on this assumption.

Researchers split 53 participants in their early-60s, who had no chronic disease but at least one risk factor for, or a family history of, type 2 diabetes (T2DM), and put them all on an aerobic exercise training (AET) regimen for 12 weeks. One group received metformin (titrated up to 2,000 mg/d in most cases; 1,000 mg twice daily) while the other got a placebo. The AET consisted of 3x/wk of 45-minute sessions at about 85% of their max heart rate on a treadmill, elliptical, or exercise bike.

In a nutshell, the study showed that metformin diminished improvements in skeletal muscle mitochondrial respiration, CRF, and whole-body insulin sensitivity after AET. The investigators suggested that metformin prevented an increase in skeletal muscle mitochondrial respiration without affecting protein synthesis. This wasn’t the first study to show that metformin can lower the exercise-induced improvements in CRF and insulin sensitivity in people without diabetes, as a 2010 and 2012 study had similar findings. Not only that, there are preliminary findings that metformin may inhibit skeletal muscle mass gains in response to resistance training in the elderly.

If we take these findings at face value, what the heck is going on here? Metformin is somehow interfering with adaptations to exercise. Allow me to speculate for a moment. Metformin is known to be anti-inflammatory and reduces reactive oxygen species (ROS) and oxidative stress. All good things, right?

From a “chronic” perspective, sure, which may partly explain its benefits in a chronic disease like T2DM that’s related to chronic inflammation and oxidative stress (as is aging: inflammaging, anyone?). However, from an “acute” perspective, exercise is also pro-inflammatory and ROS-promoting. These are part of a signaling network involved in the exercise-induced adaptations discussed above. Remember the story of antioxidants and the exercise-induced effects of exercise?

Something similar might be going on with metformin and exercise. ROS, cytokines, and myokines, for example, are involved in the adaptation process. If metformin is blunting these signals, it’s interfering with the adaptation. The perceived stress in the body may be artificially attenuated by the drug and therefore the compensatory response is, too.  I will save you from all of the gory details in this email, but I may elaborate on the mechanisms and biochemistry down the road.

So, if you’re a relatively healthy person that exercises regularly and takes metformin as an anti-aging drug, should you continue taking metformin? I don’t think there’s a black and white answer at this point and it depends on how you personally respond. In the most recent study, there was a high amount of variability in the metformin group in their response to exercise-induced adaptations. For me, in response to these papers, along with my personal experience of seeing slightly higher lactate levels during zone 2 training(suggesting, perhaps, less mitochondrial efficiency), I’ve reduced my dose of metformin and only take it in the evening in an effort to reduce the amount of metformin in my system when I’m awake and exercising.

Maybe there’s an optimal dosing, timing, and scheduling of metformin, fasting, nutritional makeup, and exercise that’s superior to placebo. Maybe not. And it depends on your makeup and your individual response. As they say in the sports world, that’s why they play the game. While it can be frustrating not having the answers, to paraphrase Richard Feynman, there’s a pleasure in finding things out.

– Peter

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  1. Peter,

    If concluding exercise in the early morning, and or are taking a rest day, would you still exclusively take Metformin in the evening, or (have you considered) also taking it mid day / lunch?



    • Can’t really say as we don’t fully understand the exercise vs metformin pathways; also, what is the envelope during which metformin is effective in cells; does metformin prevent oxidative stress, thus leading to longevity without stressful exercise and creating oxidative substances; does metformin have an impact sarcopenia and osteopenia; the question then becomes mere extra years vs quality years-same AUC but with attenuation of y axis but increase in x axis = same AUC, but different shape, maybe different slope; maybe it invites choices. Yes Professor Feynman, much joy lies ahead.

  2. This is really going to mess people up. They need more study here. Does everything to do with aging and health have to involve these catch 22 scenarios? It’s frustrating as hell. I just want to control my blood glucose levels AND get the benefits of exercise. Why can’t I have both? Exercise is certainly not helping on its own with blood sugar and insulin sensitivity I can tell you that much. Changes in diet is limited to how little pleasure in life I want to have, apparently health is having no pleasure at all… except for the very lucky few who happen to enjoy their veggies and have no sweet tooth whatsoever.

    • Nathan,
      I am not a MD, but I have been a Type 1 diabetic for 31 years (51yo male). I use Humalog in an omnipod insulin pump and I use a Dexcom G6 CGM. Based on my personal experience I can say without a doubt that exercise will lower my blood sugar independent of insulin. Whether it is increased insulin sensitivity or a pathway that is turned on with exercise, I do not know. But….The only times I have seen a flat line in my blood sugar on my G6 is when I eat a log carb diet. I deviate and I see the peaks and valleys. I eat mostly a ketogenic diet and do not feel deprived. One the keto diet I use on average 20u of insulin per day which includes bolus and basal. I could only imagine that If I were a Type 2 that I would have no need for medication to treat my diabetes. If I need a sweet, I make a fat bomb (recipes everywhere online). I like meat and veges and fat for that matter so on a day-to-day basis do not feel deprived. If I choose to cheat, I know I will suffer for couple days and I am fine with that.

  3. Hi Peter, I’ve been looking into blood flow, chronic disease, inflammation and aging. Concerning the recent publication on exercise and metformin, there has been some alarming reports that give us pause from taking metformin as a preventive measure. I have advocated for taking metformin prophylactically along with exercise to decrease inflammation, increase blood flow, and reduce chronic disease like diabetes. You should look at two recent publication on exercise and metformin, one by Viskochil in 2017, and Eltonsy in 2019. These two articles support taking metformin with exercise. In fact, combination therapy is necessary to avert diabetes in prediabetic adults.

  4. I am with you Peter on this, I also reduced my dose of Metformin from 1500mg to 500mg on weight lifting days and only take it in the evening in an effort to reduce the amount of it in my system.

    • This! And the first comment.

      It seems to me that adverse effects of Metformins effect the workout itself, if I take Metformin at night, it means I will be taking it extremely close to my 5am workout (5 days Monday through Friday)

      If I take it with breakfast immediately AFTER my workout (I train fasted), it would be the farthest possible away from interfering with the workout itself.

      However would it then somehow interfere with recovery?

      So far the studies only show a decrease in the body’s ability to have a great workout, and not much about recovery.

      With the current data list workout seems best to me.

  5. Many things still seem unclear.
    My idea now is the following:
    3 weeks of hard training (endurance and strength) WITHOUT metformin > INTO > 1 week of recovery and light training (stretching, mobility) with 1,000mg of metformin daily.

    In my mind, this way I get the best of both worlds. Maximum success through the training and through the week of recovery (with metformin) a good clean up program for the body.

    What do you think about this approach?

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