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What Exercise Authorities Don’t Tell You About Optimal Duration

Physical fitness authorities seem to have fallen into the same trap as the nutrition authorities, recommending what they think may be achievable, rather than simply informing us of what the science says and letting us make up our own minds.

Researchers who accept grants from The Coca-Cola Company may call physical inactivity “the biggest public health problem of the 21st century,” but, in actually, physical inactivity ranks down at number five in terms of risk factors for death in the United States and even lower in terms of risk factors for disability, as you can see at 0:17 in my video How Much Should You Exercise? What’s more, inactivity barely makes the top ten globally. As we’ve learned, diet is our greatest killer by far, followed by smoking.

Of course, that doesn’t mean you can just sit on the couch all day. Exercise can help with mental health, cognitive health, sleep quality, cancer prevention, immune function, high blood pressure, and life span extension, topics I cover in some of my other videos. If the U.S. population collectively exercised enough to shave just 1 percent off the national body mass index, 2 million cases of diabetes, one and a half million cases of heart disease and stroke, and 100,000 cases of cancer might be prevented.

Ideally, how much should we exercise? The latest official “Physical Activity Guidelines for Americans” recommends adults get at least 150 minutes a week of moderate aerobic exercise, which comes out to be a little more than 20 minutes a day. That is actually down from previous recommendations from the Surgeon General, as well as from the Centers for Disease Control and Prevention (CDC) and the American College of Sports Medicine, which jointly recommend at least 30 minutes each day. The exercise authorities seem to have fallen into the same trap as the nutrition authorities, recommending what they think may be achievable, rather than simply informing us what the science says and letting us make up our own minds. They already emphasize that “some” physical activity “is better than none,” so why not stop patronizing the public and just tell everyone the truth?

As you can see at 2:16 in my video, walking 150 minutes a week is better than walking 60 minutes a week, and following the current recommendations for 150 minutes appears to reduce your overall mortality rate by 7 percent compared with being sedentary. Walking for just 60 minutes a week only drops your mortality rate about 3 percent, but walking 300 minutes weekly lowers overall mortality by 14 percent. So, walking twice as long—40 minutes a day compared with the recommended 20 daily minutes—yields twice the benefit. And, an hour-long walk each day may reduce mortality by 24 percent. I use walking as an example because it’s an exercise nearly everyone can do, but the same applies to other moderate-intensity activities, such as gardening or cycling.

A meta-analysis of physical activity dose and longevity found that the equivalent of about an hour a day of brisk walking at four miles per hour was good, but 90 minutes was even better. What about more than 90 minutes? Unfortunately, so few people exercise that much every day that there weren’t enough studies to compile a higher category. If we know 90 minutes of exercise a day is better than 60 minutes, which is better than 30 minutes, why is the recommendation only 20 minutes? I understand that only about half of Americans even make the recommended 20 daily minutes, so the authorities are just hoping to nudge people in the right direction. It’s like the Dietary Guidelines for Americans advising us to “eat less…candy.” If only they’d just give it to us straight. That’s what I try to do with

Most of the content in my book How Not to Die came from my video research, but this particular video actually sprung from the book. I wanted to include exercise in my Daily Dozen list, but needed to do this research to see what was the best “serving size.”

I wish someone would start some kind of website to review the exercise literature. I’ve got my brain full with the nutrition stuff—though there’s so much good information I don’t have time to review that there could be ten more sites just covering nutritional science!

For more on all that exercise can do for our bodies and minds, see

Some tips for maximizing the benefits:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

54 responses to “What Exercise Authorities Don’t Tell You About Optimal Duration

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  1. This is a timely article. With the coronavirus lock downs of past months, I hear many complaints of people suffering depression, anxiety, and expanding waistlines due to over-eating and lack of exercise.

    It has not helped that many facilities/clubs/gyms have closed down leaving regular exercisers without their usual resources. Very frustrating.

    UK prime minister Boris Johnson survived hospitalization for covid 19 but says his own excess weight complicated his health issues.
    As a result, new programs for diet and exercise are being recommended, including prescriptions for cycling.

  2. I remember reading about the last tribe in Africa who could capture their prey by running it down, sometimes taking days or the Mexican indigenous tribe who run huge distances for fun. Wearing regular clothes and home made sandals, they have just stepped into world class ultra distance races and even win, or the woman from Nepal who ran up and down the very steep hills of her father’s farm. When soldiers saw her running, they suggested she enter a race the next day and won. She ultimately became the greatest mountaintop ultra runner. My brother and I simply ran for fun as kids. I ran 120 miles/week for years and ran races until 65 when severe spinal stenosis and multiple surgeries stopped me. My wife and I still walk 1-2 hours/day, surf, or play tennis at 71. Our goal is not necessarily to live the longest but to enjoy being active while we live

    1. Wife and I cycle. I’m mostly retired and target 5000 mi/yr at 15 mph. We just bought a Peloton for Covid and target 40 minutes on non-cycling days.

      All of my cycling friends up to age 80 are in similar shape and go 50 mi or more on Saturdays. Most work in some kind of weight training.

      We consider walking a byproduct of staying healthy. None of this is considered “exercise “. It’s simply fun and minimum body maintenance.

  3. I do high intensity training ( HIT) not (HIIT) for 30 mins 1x week- I work my major muscle groups to exhaustion getting down to muscle fibers closest to the bone. Otherwise I cycle occasionally and dog walk a lot!
    For 62 I’m in decent shape.

  4. These are probably retrospective studies, which tend to be weak. The problem is correlation – people who are healthier are ABLE to take long brisk walks. The arrow is in the other direction.

    1. Arthur,


      It seems pretty consistent in the dose-dependency.

      If you use Age 75 as a death age,

      300 minutes = 10.5 extra years
      150 minutes = 5.25 extra years
      60 minutes = 2.25 extra years

      The dose is so exact that I would think it might be real.

      1. These are just averages that have probably been rounded to the nearest 3 months.

        Google ‘spurious precision’ or ‘false precision’.

    2. In addition to aerobic exercise, it is important to engage in some sort of strength training, especially when older to prevent muscle loss. After ~60 the rate of muscle loss accelerates with each decade unless one actively prevents it. I do not think the importance of strength training receives enough focus in many discussions of exercise. It’s a pity.

      Cf. e.g. the recent post by Dr. Mirkin, noted sports medicine expert, on this issue.

      Here are some snippets but the entire article is worth reading.

      “When you become inactive, you lose your skeletal muscles at an alarming rate, and losing skeletal muscle causes loss of heart muscle until your heart can become too weak to pump blood to your brain and you die.

      In 1914, Dr. Ernest Starling described what is today known as Starling’s Law, that strengthening skeletal muscles strengthens heart muscle and not the other way around (Circulation, 2002;106(23):2986-2992). …

      On the basis of these and many other studies, this means that not using your legs and arms causes loss of nerves, which causes loss of muscles (particularly heart muscle), that can eventually lead to heart failure and death.
      • The larger your skeletal muscles, the stronger your heart and the lower your chance of suffering heart attacks and heart disease (J Epidem & Comm Health, Nov 11, 2019).
      • The less you exercise, the weaker your heart and the more likely you are to become diabetic (Diabetes Care, 2002; 25:1612–1618).
      • The larger your muscles, the less likely you are to die of heart diseases (Am J of Cardiology, Apr 15, 2016;117(8):1355-1360).
      • A study of almost a million adults with no history of heart disease followed for 10 years found that those who did not exercise were at 65 percent increased risk for strokes and heart attacks, the same rate as that found for smoking (Euro J of Prev Cardiology, Feb 10, 2020).
      • A study of 900 heart failure patients found that those who did not exercise were twice as likely to die within three years (Am J Cardiol, 2016 Apr 1; 117(7): 1135–1143).
      • A study of 51,451 participants, followed for 12.5 years, found a strong association between exercise and decreased risk for heart failure (J Amer Col of Cardiol, Mar 2017;69(9)).
      • A study of 378 older adults showed that the smaller the muscles in their arms, legs and trunk, the smaller and weaker the upper and lower chambers of their hearts (J Am Geriatr Soc, Dec 2019;67:2568-2573).
      • Low skeletal muscle size predicted death in people who had chronic heart failure (Cardiology, March 25, 2019).

      The people who lose the most skeletal muscle are usually the ones who die earliest. They are also most at risk for falls and broken bones.

      Preventing Muscle Loss
      Resistance exercise increases muscle size and strength in older people, but with aging you need to work longer to gain the amount of strength that a younger person would get with the same program (Med Sci Sports Exerc, 2011;43(2):249–58). Competitive masters athletes, 40 to 80 years old, who train four to five times per week, lose far less muscle size or strength than their non-exercising peers (The Physician and Sportsmedicine, October 2011;39(3):172-8). Eighty-year-old men who still compete in sports have been found to have more muscle fibers than inactive younger men (Journal of Applied Physiology, March 24, 2016). Inactivity causes rapid loss of muscle size and strength. If you inactivate a leg by putting it in a cast, you lose a significant amount of muscle size in just four days (Nutrition, Acta Physiol (Oxf), March 2014;210(3):628-41). Prolonged periods of inactivity due to bed rest, injured nerves, casting or even decreasing the force of gravity (in astronauts) causes loss of muscle tissue which leads to insulin resistance, higher blood sugar levels and increased risk for diabetes (Med Hypotheses, 2007;69(2):310-21).”

      Use it or lose it.

      1. I want to emphasize 言語学者 (gengo-gakusha)’s reference of Dr. Gabe Mirkin’s website This is the best, research-based fitness website I have found. It is a great complement to NF. I read it every week and have adjusted much of my workout as a result of Dr. Mirkin’s advice. For example, I’ve incorporated twice weekly short interval training (SIT) into my routine after reviewing the growing body of evidence demonstrating exercise intensity is more effective than duration for increasing aerobic fitness and other benefits. And of course regular resistance training is essential, too.

  5. Going for a walk or bike ride primarily to get some exercise is good, but I’ve found that if I can get my exercise in the process of getting other things done, I get more exercise. Like walking or biking to the store, library, appointments. Fortunately, I currently live in an area where I can do this. I know, and have lived in, lots of places in the U.S. where it’s just not feasible or safe. Darn car-centric culture!

    1. Yes!

      I lived for a while in the UK and in Korea. There I was able to do a lot of walking to get around and I had zero problems keeping my weight in check. Here, it’s another story.

      We really do need to consider how walkable our communities are.

    2. I agree Dharma! I have been getting up at 6am to ride my bike every morning since I bought it 2 months ago. It’s great for preserving muscle, and I enjoy it. But the daily activity in and around walking to the store or other errands, walking the dogs, etc is really helping to increase energy and fitness levels.

      1. Barb,

        I’m impressed. Do you eat breakfast first?

        I’m too hungry in the morning to exercise before breakfast; and after breakfast, I need some time to digest. So I eat some breakfast before and after going for a walk, or other activities.

        That’s one reason I don’t do fasting blood tests: I can’t last through the test. Too hungry.

        1. Hey Dr J, before I got the bike, I ate breakfast before doing any longer bout of exercise. Walking on hilly trails, swimming, or gym time was just too much to do on a completely empty stomach. I would eat maybe an hour prior, or more, to be energized but comfortable.

          When I got the bike it was more about safety and the luxury of having the roads almost all to myself. I try to sneak out without waking the dogs, ride for 45 min or so, then back to take the dogs out briefly before breakfast.
          Walking is in the morning sometime usually.

          When I first started, early morning dog walkers, joggers etc were very kind… some wondered what I was doing, but were very supportive when I told them I hadnt been on a bike in 50 years. A lady told me yesterday that I was ‘improving’ a lot. lol. Several said they would dust off their bikes and join me.

    3. I agree Dharma. If you are a parent, you can’t get everything done. You need two-fers and three-fers. Ride your bike to work is at least a 3 fer: get to work, get exercise, decrease pollution. Ride a bike with your kids-they get exercise, you too, and maybe you go somewhere fun: 3 fer. Shuttle while canoeing or kayaking-cross training, you decrease pollution on the shuttle, you save money from not buying gas, and you got to visit (with your spouse during covid 19) on the shuttle: 4 fer!

  6. I have exercised pretty steadily since about age 6-7, swimming, biking, running, walking. The biggest issue with getting 90 minutes a day is I HAVE A JOB and a FAMILY….and I’m a business owner, too! So 200 minutes a week is about what I can average until the laundry does it self and the employees self manage….

    1. Mary,

      You are almost there.

      Let’s see, a math person could do it off the top of their heads. I will guess you are about 6.56 extra years, but I am just guessing. Somebody else has to do the actual math.

      300 minutes = 10.5 extra years
      150 minutes = 5.25 extra years
      60 minutes = 2.25 extra years

    1. Yes, Dana! It all adds up… whatever you can fit into your day. Doesn’t have to be in 1 or 2 time slots.. break it up however works best for your schedule.

    2. Yes, many fitness experts have stressed that you do not have to obtain all your exercise in one sitting (or is that walking?!) Actually there are benefits from walking post eating or to relieve stress throughout the day. The only disadvantage of breaking up your exercise is the need to re-motivate yourself to get out there 3X rather than just once! Enjoy the walk(s)!

  7. I really like your idea of a FitnessFacts website. My regular work as a nutritionist is on hold right now, as is my work as a fitness instructor. I think I might attempt to start such a website!

    1. Catherine, Dr Mirkin is my go-to source for info.
      He is board certified in four (!) specialties including sports medicine. His website offers the newest news in exercise , nutrition, medical news …all evidence based. He and his wife are wfpb, with a bit of fish a couple of times per week. Check it out!

  8. Perhaps the man to review the exercise literature is James Smith PT. He’s all about cutting through the BS!
    Or perhaps Cori from as she seems to have a scientific approach.

  9. At 63 I do 30 minutes a day of moderate aerobics, everyday.I am vegan, healthy and about 10 lbs over my ideal weight. I do the normal household chores, and my bathroom is on the second floor. I can’t do more or I’m exhausted. I think each person has to decide how much exercise is enough.

  10. How can (many) wild animals be so extremely strong, agile and fit? Without exercising?

    I have walked, hiked and camped a lot in forests and mountain areas. In total, I have slept a couple of years out in the wilderness.
    I have met a huge variety of wild animals, all year round.
    As a 10-year-old, I loved tracking animals in the snow: hares, foxes, badgers, deer and moose. They did not move far during the day.

    I have never seen wild animals exercise.
    What’s their secret?

    1. Well, they don’t have armchairs, labour-saving devices or motor cars. Perhaps their activities of daily living require considerable physical activity rendering exercise unnecessary?

    2. Wild animals stay fit, for their short lives, by traveling miles and miles a day for food, and to avoid from becoming food. They work out, every day of their lives, to stay alive., and there is rarely food security. They stop to rest, before doing it all over again. As they are not people, who live in houses and do food gathering from a cold box inside those houses, they get plenty of movement. But that’s not anything close to an optimal life. Living wild never ends well. For example, cats living wild last about 4 years. In my house they last 17. Lots of variables go into optimal health, For humans, at this point in our evolution, the science says the right food and the right amount of movement are the top 2 variables. Avoiding bad habits, I would say, is the 3rd.

  11. My gym’s closed currently, but I remember being impressed there one week when twice people were carried out on gurneys by Medic One.

    It seems to me exercise can raise risk if diet is not right. An atherogenic diet in particular would appear to make arteries vulnerable. But the public seems to think if I exercise I can eat anything I want. I believe the reality is if I eat right, I can exercise all I want, and nobody wants that reality, so they choose to delude themselves into a deadly pattern of priming the arteries with weakness via bad diet, then exacerbating the situation with vigorous exercise that raises blood flow and pressure tearing things apart and resulting in heart attacks and strokes. I’d say get the arteries in shape first with whole food plant-based diet, then have at the gym, if you want to do it all safely, if not, you don’t need to bother with exercise, it will likely make things worse.

    1. A check up first is important but starting slow is as well. It’s a journey, no need to rush. I love Amby Burfoots approach to running forever, GO SLOW. When I started running, I did so after a check up and going plant based and going off added fats and oils for a few weeks before I began training. You don’t have to wait forever to start, but start smart. I started running at 60. Paired with a whole food plant based diet, movement can can enhance your live tremendously.

  12. I’m 77 years old and exercise six times/week, 3 days of walking 5 mi. each and 3 days of moderate lifting in the gym, (in addition to WFPB eating). I’ve never felt better. I have no joint pain and the problems I’ve eliminated are too numerous to mention including NO heel spurs, shin splints, improved kidney function, lower cholesterol (153) and BP (110/53). No medication except for one tablet/day for enlarged prostrate due to years of eating SAD. Physically, I can do things I was able to do 40 years ago.

    1. Brian Howe:
      Congrat’s on your routine and health – very impressive at 77! Question: there are several older men in my life who also have an enlarged prostrate …. before I do my own research, please expand on the correlation between that and the SAD frm your experience. Thank you!

    2. Wow, Brian, that’s great! I’m 62 and working up to 4 miles of walking right now about 3-4 days a week and then 3 days of strength workouts. I don’t like gyms plus can’t afford them but I have what I need at home. I’m vegan and 15 pounds over my “normal for my height ” weight in high school. I notice that joint pain and blood pressure both are healthy as long as I stay active. No meds for me. :-)

  13. How long to exercise for maximum health or lifespan is complicated by many factors, which the data given do not take into account. Your example of walking say 10 hours a week being better than 3.5, will apply differently to those with different DNA as you would know better than I.. Some may have marginal hip and knee joints, some polluted air outside, and although myself an exercise addict, I often remind others that Stephen Hawkins with MND from 21 years of age, survived whilst in a a wheel chair or bed for the next 51 years, living longer that Mohamed Ali and many football players. By all means publish !!

  14. I can’t believe that we don’t know how much and what type of exercise is optimal! Clearly, running marathons is destructive; leads to extra colds and whatnot. Maybe a daily 10K run would be optimal? Weight-bearing helps bone health, but at what point do you wear down the joints to eventually require knee or hip replacements?

  15. To be fair, there is evidence that the 150 minutes per week recommended in the US Guidelines is a sensible goal and that additional activity is unlikely to deliver significant benefits (on average and all other things being equal)

    ‘ the associations were strong and consistent and the takeaway message seems straightforward, according to the researchers.

    Anyone who is physically capable of activity should try to “reach at least 150 minutes of physical activity per week and have around 20 to 30 minutes of that be vigorous activity,” says Klaus Gebel, a senior research fellow at James Cook University in Cairns, Australia, who led the second study. And a larger dose, for those who are so inclined, does not seem to be unsafe, he said.’

  16. Dr. Greger,
    If you want to get into excellent shape fast, go up.
    Walking uphill can burn many more calories than walking on level ground. Of course your speed will slow down, but it still raises your workout level substantially.
    Let’s say compared to walking on level ground at a speed of 3.5 miles per hour, a 6% incline will increase energy expend by 16% walking the at same speed. Walking on a 15% incline at 2.5 MPH will burn 67%
    more calories than walking on level ground at 3.5 MPH. Walking at 2 MPH on a 20% incline will burn 70% more calories than walking on level ground at 3.5 MPH.

  17. I seem to remember some studies that showed antioxidant levels could rise quite sharply from over exercising. There seems to be a sweet spot (where you can get lots of benefits from exercising and reduced risk to lots of conditions) but then balance can easily be shifted into the negative zone if you overdo things. The $60 million question is where is that perfect sweet spot? I guess it could be an individual thing. If you exercise to exhaustion then that’s perhaps not good for you? I’ll be 60 soon and have exercised a lot since my 20s. Taught aerobics, spinning and power yoga classes. I ate sugar free and mostly whole foods from the age of 27 and turned vegan (raw to start with) when I was 39. I’m sure that has contributed significantly to my fitness. I now run twice a week, do long walks (with a lot of uphill), spinning and cycling, HIIT classes twice a week and weight train 5x a week to maintain muscle mass. I feel good but also make sure I have at least one rest/recovery day a week when I meander rather than the brisk walking I normally do. I’d be very interested in more studies in this area.

  18. The entire exercise industry is based on poor research and misinformation. Even this article, takes a lot of liberties with the “data” that is available in regards to what is exercise, how much exercise is necessary, how often throughout the day, what type of exercise, exercise intensity, and the negative effects of exercise, and exercise’s dependency and connection to nutrition. I have been in the diet and fitness industry for a long time, and will argue till I am blue in the face that the majority of folk would benefit most from going to the store, shopping and cooking plant-based meals, cleaning our houses, doing yard work, and walking around our neighborhoods for 15 minutes after meals than doing any type of “workout.” I really appreciate this website and highly respect Dr. G. I went plant-based and started walking 6 years ago, and left behind the diet and fitness industry/heavy and hard daily workouts, and high protein-low carb diet that I did and taught people how to do for 15 years. The last 6 years has been the easiest thing that I have ever done.

    Exercise, like nutrition has become so distorted and fragmented, and any talk about “exercise and calorie burn” or using exercise as a means to end to get a result has completely missed the point of what exercise is and what it is designed to do. Walking like fruit is good for you, invite a friend, bring your pet, and go outside to be in nature, get some sun, bring some water, don’t wear your headphones, let the sounds of silence and nature be your background noise and remember every step nourishes you.

  19. The website founded by Dr.Kenneth Cooper was my source of exercise studies that were done by Dr. Cooper starting back in the 1970’s. I believe he coined the term “aerobics” and provided details on aerobic exercise in his books including the “Aerobics Way”.

  20. Dr G, I have been following you for years. I’ve bought your books and I subscribe to your videos, I love your work!!!! Do you think you will ever come to Australia…? After COVID of course!

  21. Dear Nutrition Facts,
    In another talk Dr Greger made a similar suggestion for people to start a – I am writing to ask if you could consider just doing about 30 videos on this topic – it would reach so many people. Already you have videos on pesticides, climate, air pollution. Please give this some serious consideration,
    James O’Donovan

  22. Where does the 4 miles per hour come from? My husband is over 6 ft tall and can do that easily. I however, am just over 5 feet tall and 3 mph with my short legs, even with shorter steps, is a workout physically. I feel like my legs are going to fly off. Running is actually more comfortable. Adding hills gets my heart rate up more effectively when I walk. Should heart rate really be the test? Even that will change every few weeks.

  23. In studying for my personal trainer certification, the literature presented stated the 50 minutes of hard aerobic exercise (time in aerobic range) was about the point of diminishing returns. That does not answer the upper limit question. Considering their position on diet, I wonder how good that is.

  24. Take advantage of helpful electronics such as FitBit and others. They record steps, activity level, time spent and even buzz on your wrist to remind you its time to get going. Mine happens to be set to buzz 10 minutes before the hour, letting me know that I have only 10 minutes to accomplish what I have preset as an hourly goal. Keeps me off my back side and if I’m a bit late, you can see me running or up and down the stairs. When the goal is accomplished, there’s a firecracker blazing on my wrist with congrats or well done. I’ve very rarely missed my personal goal and feel great (or proud) of myself. Big grin here. Be well. Device is very inexpensive. Cheapest I could find.

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