• Dr Sajad Zalzala

Metformin & Exercise: A Q&A with Dr. Zalzala



Are you concerned taking Metformin could impair your exercise progress? If so, you’re not alone. Until recently, research suggested Metformin may hinder some of the beneficial effects of endurance, resistance, or combined exercise training. However, a study published in October 2020 found that Metformin increased gene expression of aging relevant pathways, which were not activated in people who just exercised and did not take Metformin—suggesting exercising plus Metformin is healthier from an aging perspective than exercising alone.


With more and more research surrounding Metformin and exercise becoming available, I routinely field questions from patients about the topic. To help further explain the effects of Metformin on exercise, I’ve listed the most common questions and answers below.


Why is it that Metformin patients don’t gain as much muscle mass?

Metformin users certainly still gain muscle mass, but not as much as the non-Metformin users. I have a couple theories as to why:

  1. Muscles "bulk up" due to the damage done during exercise. Additionally, it’s thought that Metformin makes the muscle cells more potentially efficient and, therefore, does not sustain as much damage.

  2. Metformin is thought to have slight mTOR inhibition, as well as mimics calorie restriction, and, therefore, the muscles may favor repair over growth.

Does this only affect diabetic patients who take Metformin for their diabetes?

I do not believe so. The two most recent studies (referenced here) claim participants were non-diabetics.

If I’m taking Metformin for longevity purposes only, will I also have issues gaining muscle mass? Can I still strengthen and tone my muscles?

If you are just trying to gain muscle mass and strength simply to be healthier, then taking Metformin does not seem to be an issue.


If you are looking to "bulk up" for a competition or to reach specific performance goals, such as a marathon or bodybuilding competition, then I would recommend you skip Metformin until after your competition or until you’ve met your goals.


Should I switch to IR Metformin if I exercise a lot? How do the effects differ between ER and IR Metformin?

Without going into too much detail, at this point it seems to be a matter of opinion. If you ask one of the biggest experts on metformin, Dr. Nir Barzilai, Extended Release (ER) Metformin will be used in the TAME trial.

At AgelessRx, we primarily prescribe ER Metformin for two reasons:

  1. It’s easier to take (once daily vs twice a day)

  2. It’s easier on the stomach (far lower discontinuation rate due to diarrhea/cramps)

One could argue that you get higher peak Metformin levels with IR over ER, but we don't know if that translates to better longevity results (or worse!).

In my medical opinion, I think the only reason I would possibly recommend IR over ER is for people who want it "out of their system" in time for heavy physical activity—but, even then, I think the effects of Metformin might stick around well after the medication is out of the system.

What forms of exercise should be avoided with Metformin?

Typically, I encourage patients to skip Metformin if they are training for a major event, such as a marathon, bodybuilding competition, triathlete, iron man, etc.

Is there any science regarding Metformin’s impact on regular cardiovascular activities?

Yes, and more research is still needed. A 2010 study suggested that Metformin (at higher doses than prescribed at AgelessRx) may reduce some of the benefits of exercise. This is because Metformin is thought to reduce oxidative stress; this same stress is supposed to help improve aerobic function.

It’s not clear if lower doses or skipping doses can help reduce this, however, it is our general recommendation at AgelessRx that hardcore athletes who do engage in more strenuous exercise all the time might want to skip Metformin altogether until more research is conducted.

Should I continue to take Metformin as prescribed if I do choose to skip a dose or go off of it for some time?

If you skip a dose here and there, I don’t see any reason why you could not resume your dose, as directed.


If you skip Metformin for an extended period of time, such as months, I usually recommend a ramp-up period over 10 to 14 days to lessen any gastrointestinal side effects you may experience.


Until next time!


Dr. Z


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To learn more about Metformin, click here.


To request a Metformin prescription, click here.


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