Dear Mark: Metformin for Life Extension, Too Many MEDs, MED for Lifting Addict, and Horseback Riding

For today’s edition of Dear Mark, I’m answering four questions. First, does the diabetes drug metformin have life-extending potential for non-diabetics? Then, the final three questions come from the comment board of last week’s Minimum Effective Dose post. First, is it possible to try to do too many minimum effective dose workouts in a week. Yes, absolutely. I explain why a reader who seems to want to incorporate every single routine listed in last week’s post probably shouldn’t try. Next, what if someone truly loves training? Should he or she still try to figure out the minimum effective dose for his workouts? And finally, is horseback riding an effective stand-in for walking?

Let’s go:

I wondered if you had seen the New Scientist article on the anti-ageing metformin study being undertaken? Increases life expectancy, lowers heart disease and cancer risk …oh, and it’s a diabetes drug, so it works on lowering blood glucose! Which I imagine a primal blueprint would do too…


I haven’t seen the New Scientist article (it’s behind a paywall), but I am aware of the generally positive research being done on metformin. It’s becoming increasingly clear that not only diabetes patients may be able to benefit from metformin. Robb Wolf was beating this drum back in 2012.

There are many indications of metformin’s life-extending potential:

Metformin activates AMPK, the same autophagy pathway activated by exercise, fasting, polyphenol consumption, and reduced calorie intake.

Metformin also seems to protect against many of the conditions that kill people, like cancer. It lowers hyperinsulinemia and may protect against insulin-related cancers (breast, colon, etc). Early treatment during adolesence, for example, protects rats against later tumor growth.

Type 2 diabetics (a population with lower overall mortality) who take metformin live longer than age-matched controls who don’t have diabetes. That’s huge.

Metformin appears to work on lifespan via hormesis. Diabetics who need it just to keep their blood sugar in check are taking (and should take) it regularly, but if you’re just an experimenter interested in potential life extension, treating it like a hormetic input like fasting or intense exercise is probably a better, safer approach.

It appears that metformin may also act via modulation of the gut bacteria (surprise, surprise). It increases mucus production in the gut, which the resident bacteria are able to feed upon and increase in strength and number. It’s been shown to boost Akkermensia count, the strain commonly linked to leanness and anti-diabetic effects. Some studies have even shown that Akkermensia can improve gut barrier function in obese subjects, so metformin may be especially helpful for this population. Additional effects include reduced carb absorption by the host (that’s you), leaving more to be consumed by gut bacteria (a la resistant starch).

Berberine might be a “natural alternative” to metformin. Like metformin, berberine can activate AMPK, lower blood sugar and improve blood sugar control, and enhance short chain fatty acid production by gut bacteria. Being a whole plant extract, berberine isn’t identical to metformin, so I wouldn’t suggest diabetics switch without consulting their doctor, but it is a promising alternative that doesn’t require a prescription.

Overall, metformin looks promising. I’m not sure it’s an essential part of a longevity-promoting regimen if you’re already fasting, training, and eating colorful polyphenol-rich fruits, vegetables, spices, and dark chocolate, but I’m certainly open to the idea and await further research.

Hi, Mark,

Thank you. Would you be so kind to say a few words? What regime could work, as you stated doing all of them would make the workout protocol too strenuous and ineffective?

Is my idea below on the protocol OK?
week 1
MON 5x 4-minutes intervals
TUE 30-sec bike sprints
WED Tabata
THU 4-sec all-out sprints
FRI Tabata
SAT 30-sec bike sprints
SUN rest day

week 2
MON 7-minute workout
TUE 4-sec all-out sprints
WED Tabata
THU 30-sec bike sprints
FRI Tabata
SAT 4-sec all-out sprints
SUN rest day

Walking daily.

Can I add sprint intervals to Tabata day instead of doing them on a separate day?

Wish you all happy workouts, 🙂


I’d argue that the sprints, the Tabata intervals, and the 4-minute intervals are mutually exclusive. Your suggested weekly regimens are pretty rough and, for most people —including elite athletes — impossible to keep up with.

You must realize that in most of those studies, researchers precluded subjects from doing extra training. Since they were only interested in testing the effects of specific workout volumes, allowing them to engage in other types of workouts would only weaken and confound the results. The soccer player study with the 4-minute intervals was the only one to my knowledge that allowed other training on the side.

Let’s take your first week. Nearly all-out 87-97% max effort intervals lasting four minutes are not something you just tack on to the end of a workout. They are seriously hard. I know, because I used to run similar intervals back in my heavy training days. They’re designed almost entirely for people who aren’t doing much of anything else. And these were semi-pro soccer players doing them once every two weeks with no other formal training prescribed to them. They had two weeks to recover in between bouts. Trying to squeeze in six sprint sessions a week on consecutive days is just asking for lower results.

In fact, you might destroy your fitness and recovery by overloading the system.

Here’s what I might do to incorporate some of the protocols mentioned last week, assuming I’m trying to do the absolute minimum.

MON: 7-minute workout

TUE: 30-second bike sprints

WED: Rest

THU: 7-minute workout

FRI: 4-second all out sprints

SAT: Play (hike, pick-up game, bike, surf, swim, or even go see a movie or have a dinner party; it doesn’t always have to be physical)

SUN: Play

Walking daily? Always a good idea.

I don’t much care about my health but I enjoy lifting weights, and I like to look good, so I do as much weight lifting as I can given my age. I understand that some people do not enjoy exercising but if you’re the kind of person who does enjoy it, it’s hard to wrap your mind around the concept of minimizing time spent exercising. To me it’s like suggesting that I minimize the time I spend having sex.

I hear you, but I think we’re actually in agreement. As I was unable to find any solid evidence that very low volume strength training elicits favorable reactions to as great a degree as low volume sprints, I suspect shorter and sweeter works better for conditioning and general fitness. If you want to get big and really strong, you’ll probably need more time than a few minutes a week (although Doug McGuff’s Body By Science program might beg to differ).

Ultimately, the post was all about efficiency of exercise. Being efficient lets you maximize the effectiveness of your time in the gym. Efficiency means having more time left over to do what you truly love. If that’s lifting heavy, then go lift heavy. If that’s sex, go have sex. If it’s playing Ultimate Frisbee and standup paddling (which it is for me), go do those things with your extra time.

No matter how much you love to lift weights, you still want your time under the bar to be productive, right? Efficiency matters for you too, then.

Wondering how horseback riding stands in for walking? I ride about 45 minutes most days at moderate intensity (jumping and dressage, not noodling down the trail) and hope it’s a good stand-in, because I have trouble finding time for long walks as well.

At least in healthy kids, simulated horseback riding elicits lower cardiorespiratory responses (heart rate, energy expenditure, etc) than even slow walking on a treadmill. That was simulated riding, of course, which is probably very different from real riding. Even so, it’s likely not as metabolically demanding as walking overground, but that doesn’t make it useless. Contrary to what many people might believe, horseback riding is absolutely a form of exercise.

Now, can it replace walking? No, I doubt it. Walking is the foundation of health. But nor can walking replace horseback riding. Do both when and however you can. And if you can’t walk as much as you (or I) would like, know that it’s doing “something.”

That’s it for this week, folks. Thanks for reading and be sure to help out with your own answers and comments down below!

TAGS:  Aging, dear mark

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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41 thoughts on “Dear Mark: Metformin for Life Extension, Too Many MEDs, MED for Lifting Addict, and Horseback Riding”

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  1. Berberine is very much a YMMV diabetic supplement–it may have worked for Jimmy Moore, but didn’t do a _____ thing for my husband….well, it may have been doing things we cannot see or measure, but the BG meter wasn’t impressing either of us. He got better results by going zero carb than he did taking those pills!

    1. I had the same experience with Metformin, I get much better results by avoiding carbs. I took it initially because of the dawn effect, my blood sugar was up in the morning. It did nothing to help. What does help is to not eat after 5 p.m., especially no protein. I’m amazed at how many T2 diabetics take metformin and think it works like insulin, “I’ll just eat this donut and take an extra pill.” I find it disturbing that many diabetes drugs are taken this way, so people make no dietary changes and just keep getting worse.

  2. I can’t imagine why any healthy, non-diabetic individual would even consider taking Metformin. Like all prescription drugs, Metformin comes with potential risk and is probably best avoided if one doesn’t need it. There are better ways to extend longevity and avoid diseases.

    1. There will be a time in longevity-based medicine (not saying we’re there yet) when people take drugs not to solve any specific malady, but to extend the number or productivity of our years on earth. We’ll know we’re there when people not taking a specific drug or drugs are enjoying shorter, less productive lives generally than those who take it.

      Again, I’m not saying we’ve yet reached that point, but I believe taking a stance of “why would anyone who doesn’t have that condition take that drug” is a knee-jerk reaction to a topic that science will likely settle eventually, perhaps in support of taking a drug for “general well-being” vs. a truly theraputic use.

      Even though I don’t have diabetes, I’m going to keep an eye on this one. If I can reduce my chances of getting heart disease (my likely executioner based on family history) and extend my life with a low side effect profile, I’m taking the drug.

      Those who don’t believe in better living through chemistry, either haven’t paid enough attention to the history of chemistry, don’t understand the momentum of life sciences, or both.


      1. ‘…I believe taking a stance of “why would anyone who doesn’t have that condition take that drug” is a knee-jerk reaction…’

        Not really. It’s a known fact that drugs of any kind can disrupt the natural chemical balance of the human body. To what extent depends on a person’s individual makeup and may not be detected or understood until serious decline has set in. This sort of thing is euphemistically and cavalierly referred to by the medical and pharmaceutical industries as “side effects.”

        “Those who don’t believe in better living through chemistry, either haven’t paid enough attention to the history of chemistry, don’t understand the momentum of life sciences, or both.”

        Again, not really. Those who DO believe in “better” living through chemistry have a pretty arrogant approach to the intricate workings of the human body. I’m sure you seen numerous persons on multiple prescription drugs who have gone steadily downhill until they died. We all have, repeatedly. I wouldn’t exactly call that better living through chemistry.

        1. I think you’re missing my point.

          Of course there are benefits and side effects of any medication. That should continue to be the case as far as we can currently see.

          Anti-biotics can cure Plague. The side effect was trouble pooping and the possibility of a yeast infection.

          Chemo can kill cancer. The side effect is feeling lousy for a while and losing your hair.

          I think we’d all agree that the benefits outweigh the side effects in both of the above cases.

          I’m not saying we’ve reached a point in science where we should take drugs off-label in absence of the condition it was designed to treat. I’m not even saying that Metformin is a good idea for non-diabetics.

          But think about this research. People with Diabetes (a horrible condition that, on average, subtracts 8 years from an average life) who take Metformin live LONGER than people without Diabetes. That’s a huge, huge deal. Assuming the research is correct, they’ve stumbled upon something truly amazing, and I don’t use that word fiippantly.

          I get that 21st century pharmacology isn’t “Primal.” I further get that most of us try living primally because it makes us feel and look better and helps us “feel” like we’re living naturally, closer to the way nature intended. That the science happens to appear to support it for healthy living is just a cherry on top of what we already think we know.

          But what I’m saying is that in the not-so-distant future, there will absolutely be medications available that when taken regularly, reliably increase the number and quality of years in a lifespan with side effect profiles along the line of antibiotics.

          If, when (inevitably) this community is faced with clear science that says a medication gives you twenty or thirty extra highly productive years and the side effects are once-monthly achy toes, I hope the news won’t elicit the same knee jerk reaction this article did.

          If nothing else, I look forward to that time because it will, for good and all, separate those who follow Primal primarily because it confers superior health and wellness benefits to its adherents and those who do it out of some (real or imagined) mystic sympatico with early Man.

          I hope the above for the same reason that I believe in Mark’s integrity enough that, if faced with clear science that says Primal living improves health for the first ten years and then triggers a rapid descent into ill-health and increased morbidity, he would loudly suggest we follow another path. Good feelings aside, it’s ultimately about the science.


    2. It’s the major prescribed drug for those of us with PCOS and therefore at a higher risk of developing diabetes. I’ve been primal for a few years before I even found out what was going wrong with my body. I have no markers for diabetes (except abdominal fat that won’t go away) but it’s made me hyperinsulinemic (if you’re following at home, that does NOT mean I’m diabetic, it means my tissues are insulin resistant, even though my BG is fine, because ultimately my body is clearing it all out and making it work, but the underlying issue is there). I did a lot of due diligence before agreeing to take something that’s a “diabetic drug” when I don’t have diabetes. The fact is, anecdotally, women who haven’t ovulated in years fall pregnant on metformin. It provides balance when homeostasis is out, for whatever reason it’s out. Lots of things get cross-prescribed even when it’s not the major purpose for the drug in the first place. That’s the thing about the human body right? Everything is connected.

      1. Ah, insulin resistance is pre-diabetes. Your pancreas is still able to keep
        blood sugar in check, when it no longer can then you get a diagnosis of diabetes. Best to not go there.

        Hippocrates call fasting “The Doctor Within” and Dr. Jason Fung has
        gotten people off of diabetic drugs including people who have been on insulin for 27 years by putting them on long term fasts.

    3. I started taking Metformin because my A1c had crept up to 5.8 and after two months it retested at 5.6. Now several months later and after increasing the dose from 1000 mg/day to 1500 mg/day, I’m having increased fatigue and reduced exercise tolerance, which at age 73 was already a concern. New research is showing that, unfortunately, Metformin clearly does reduce exercise, tolerance so I will discontinue it and seek to get the A1c down through other means. Those contemplating Metformin should be aware of this new research.

  3. People who clean stalls or paddocks, and groom and tack up the horses they ride get a good workout before they even get on. I’m out at the boarding stable for 3 to 4 hours every day and ride two horses for a total of an hour to an hour and a half. I’m on my feet the rest of the time–walking, lifting, carrying, bending, pushing a muck cart, grooming, and doing ground work. Riding a posting trot or canter takes energy. When I started back riding I could barely manage one circuit of the arena at a posting trot before I was tired; now 10 minute patterns are easy. This is regular, sustained, low-level exercise that I love!

    1. Great point! I don’t have to muck stalls, but spend lots of time on my feet doing horse-related work I wouldn’t otherwise do, like hauling out and putting away jumping equipment. And it helps me stay motivated to hit the gym – kettlebell swings and Bosu ball squats have really helped my core strength and balance in the saddle.

  4. As an equestrian, I was pretty excited to see that you’re covering a horse related topic! I do endurance and it is definitely a work out- after cantering for 10 minutes both myself and my horse are out of breath.

    1. People who don’e ride have NO IDEA! I just seems like a fun thing to do to them.

      1. Controlling an animal that weighs more than you is very primal. Playing polo, jumping, running the barrels, and mucking out stalls is part of the human experience. Equine and human are symbiotic species. I’m putting hunting bison on horseback on my bucket list.

  5. Metformin is being investigated as a treatment for Alzheimer’s and the results are encouraging. I take it for diabetes.

  6. Metformin inhibits the release of glucose from the liver. While doing endurance activities I had the worst bonks ever while taking metformin.

    1. As a Type I diabetic, Metformin has done wonders for me. You have to remember that in Type I’s the closed-loop communication system between the pancreatic beta cells and the liver is broken. It’s like duct-taping a cut wire circle together – the circle is still a circle (via injected insulin) but the communication mechanism is broken. With that communication link broken, the liver releases glucose haphazardly – generally when it is LEAST needed!! If you inject insulin to deal with a meal or a high sugar reading, the liver might think “omg – there is a ton of insulin on board, I need to maintain balance” and it releases a bunch of glucose. Metformin basically tells the rogue liver to chill the hell out. I no longer get massive spikes after a work out and it has reduced my insulin requirement. The other positive thing about Metformin is that it has been around for ~80 years and, for an rx, is relatively safe.

  7. Be careful with Metformin. It has been found to feminize male fish in studies of waters below wastewater plants!
    See article in Scientific American (can’t copy/paste it here for some reason).

  8. Could cycling be a substitute for walking? Or is it like horseback riding, where it is still good, but can’t replace the walking?

    1. Definitely! There have been lots of studies on bike riding, and even small amounts each day have beneficial effects. Cycling and walking are among the best low-impact forms of exercise, and you’d probably get relatively equal results from the same time spent on a bike or on foot.

  9. It seems like all the things that Metformin “protects” against are things that are predominantly the result of an excessively sugar-based metabolism, so for someone who only sends a moderate level of sugar down their metabolic assembly line the “benefits” could well be reversed. This reminds me of the Paul Jaminet/Ron Rosedale blog post debate where Paul made an interesting case that lowering blood sugar too far is actually harmful (blood sugar potentially being a symptom, not the root cause mechanism, but still…)
    It also reminds me of the people who think everyone should be on Statins. It will be interesting to see how the science evolves, but this seems like another case of treating the symptoms of a sugar-based metabolism rather than solving the core problem by shifting to a fat-centric metabolism. In order to endorse Metformin, there would have to be a strong case that it actually is beneficial for all-cause longevity in people who are already healthy in a Primal/Ancestral way, and I can’t readily think of a population where that could be easily tested, let alone actually will be tested.

    1. Metformin has been scientifically shown to increase the profits of big Pharma companies.

  10. Metformin depletes your B 12…so if you take it you need to supplement.
    Life Extension Foundation has been touting it’s preventive use for years.

  11. “I don’t care much about my health”? Really? Why do you read this blog and ask Mark questions then?

  12. as an ICU nurse I have taken care of a few patients who have almost died from taking metformin. It causes Lactic Acidosis on some people. It can occurs right away or over time. Be warned.


    Smaller fish and intersex fish (male fish that produce eggs) are linked to Metformin in water. Like other pharmaceuticals, so many people are now on it (and excreting it into the groundwater) that animals are affected. (And maybe humans, too: how many transgender-feeling people did you know when you were young? And now?)

    Taking (and peeing out) Meformin to increase your own longevity = dubious wisdom.

    1. I concur with your point – and I’ll be happy to stand on the sidelines and wait for the inevitable nasty surprises that come out of prolonged Meformin use – just like when steroids were “discovered”, it was soon evident that like anything, you build a resistance to the drug, and end up depending on it, just to get back to “normal”.

      I suspect a dependency would be formed on Meformin for similar reasons – any shortcut to health seems to have consequences, and from your theory, its sounds like we won’t have a choice…

  14. Woohoo, my question made the article. Thanks Mark! Even though I am a runner and do stuff like all-out 500m rows, I do get out of breath doing jumping or canter dressage work, and challenge about anyone to test their fitness on taking a fast horse out for a cross-country gallop. There’s a full spectrum of metabolic demand from the rider based on the activity and intensity, and how hard the particular horse is to ride. However, much of it is isometric. Interesting factoids about balance, though they make total sense.

  15. The catch with Tabata training, like sprint interval training, is the recovery time – doing more doesn’t mean more gains. if you do it every day, or even every second day, you won’t be fully recovered, and thus won’t put your “full effort” that you could into the session – i.e. – you will burn out. Better to do 2 full effort sessions a week, than 4 half baked efforts.

    Also, I do heavy lifting sessions, and I HAVE noticed benefits, despite any so called lack of scientifically provable benefits – but I STILL do at least one or 2 weekly SPRINT/TABATA sessions of 10-15 minutes, maximum intensity.

  16. Are you kidding me? Don’t do it. At the first sign of hyperglycemia they insisted I take this drug. I have never been so sick in my life. I was constantly afraid of having a “metformin moment ” while at work…or wherever. I could not live a normal life.. I don’t care what some study says there is no stinking way this stuff is healthy.

    I am controlling my numbers with Paleo/primal or ketogenic diet (depending on what my numbers are)..

  17. Ancient tribes would render Metformin using a long forgotten and secret bush method

  18. On horseback riding, it absolutely can be a cardio exercise when you are really working at a posting trot and canter. Even when I was marathon fit, 15-20 minutes of serious trotting would have me huffing and puffing. Just sitting at a slow walk is probably not going to have the same response. Plus, when I ride, I get in a lot of walking anyway- getting the horse from the field, grooming, tacking up. It’s a pretty good session of activity.
    BUT PLEASE if you want to ride, have some base of fitness. Don’t be very unfit and start riding in hopes of getting fit. It isn’t fair to the horse. If walking a mile or two on foot is too much, then please just stick to simple walking on a horse. Don’t make the horse into your cardio machine- a lack of balance/strength and cardio makes people just flop around and annoy the horse. You at least need one of those fitness factors in place to get started correctly.

  19. Hi Mark, thanks for sharing another interesting post. I have heard a lot about how Metformin can be used for beauty and fitness other than its medicational purposes. Like some of your readers, I can really use some of the useful information that you shared here. Great read!

  20. Pffft.

    Horseback riding is most definitely more work than walking, especially at an advanced level like doing jumping and true dressage work. If you were walking around on a horse, then no. But when you are trotting and cantering and jumping, it is much more.

    So much more in fact, that when I wore a heart rate monitor, it was about the same heart rate/calorie burn as going for a 5mph run. When I am at horseshows, between riding and walking to the rings and things to support other folks showing, it’s about 22,000 steps a day. I have shown people my FitBit tally from horseshows and they are shocked.

    1. I totally concur! Although I’m not riding much anymore, when I rode and worked around horses, I was VERY fit! I laugh when people think the horse does all the work. Besides the actual riding, being around horses keeps you very active, from bending (cleaning hooves, applying boots, wraps, etc), lifting and carrying feed and equipment, raking, mucking, walking between barns, turn-outs and arenas (there’s always seems to be a giant hill between them, BTW). If you show your horse, a show probably means 4-5 days of non-stop, on your feet, activity, too. My friend trains reining horses and she is one of the fittest people I know!