What the New Study on Exercise and Longevity Really Tells Us

Authors: Alex Hutchinson

Publisher:

Outside

Published: 1/30/2026

Language:English

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Taylor

Good evening Project, I am Taylor, and this is Goose Pod, specifically for you. Today is Monday, February 02th, and the clock just struck 23:00. I am so excited to dive into a topic that has been lighting up my strategist brain all week long.

Holly

And I am Holly. It is such a pleasure to be here with you this evening. We are going to explore a fascinating new study on exercise and longevity. It is truly wonderful to consider how our daily movements weave into the long, elegant tapestry of our lives.

Taylor

We are talking about a massive study recently published in BMJ Medicine. Imagine this: researchers from Harvard followed 70,000 women and 40,000 men for over three decades. That is thirty years of data! It is like finding the ultimate narrative thread for how we actually age in the real world.

Holly

How absolutely lovely to have such a grand scale! Usually, these studies only look at a few college students for a couple of weeks. But this is different. It tells us that doing a variety of activities is actually much healthier than just sticking to one single routine.

Taylor

Exactly, the variety aspect is the headline. But here is the kicker: the data suggests that once you hit a certain amount of exercise, doing more might not actually help you live longer. They measured this using something called MET-hours, which is basically a way to track energy expenditure.

Holly

I found those colorful graphs in the study so intriguing. They showed these specific curves for different activities. For instance, walking seemed to have a very robust benefit that eventually plateaus, but then things got a bit mysterious with jogging and swimming. The shapes were all so different.

Taylor

The study claims that twenty MET-hours per week is the sweet spot. For context, that is about an hour of walking every day. If you are a runner, it is roughly one hundred minutes a week. Beyond that, the mortality risk reduction seems to level off at about thirty percent.

Holly

It makes me wonder if there is a limit to how much we should push ourselves. The researchers suggested that variety is the real spice of life here. Even if you do the same total amount of work, mixing it up leads to better outcomes for your heart and muscles.

Taylor

This variety score was a big deal. They looked at thirteen different types of exercise. People who played pickleball, jogged, and hit the gym saw more benefits than those who just did one. It connects to that memory we discussed about how brief bursts of activity can trigger anti-cancer effects.

Holly

Oh, I remember that! Just ten minutes of high-intensity movement can release molecules that help repair our DNA. It is so empowering to think that even small, varied doses of movement act as a vital, life-saving tool for our bodies as we move through the years.

Taylor

But we have to be careful with the data. Some of those curves for individual sports, like bicycling, looked a bit nonsensical. It showed that a medium amount was worse than a small amount, which usually means the data is getting a bit messy or the groups are too small.

Holly

That is a very sophisticated point. We must be mindful not to just pick the results that sound nice while ignoring the ones that look odd. It reminds me of that ancient physician Galen, who said everyone recovers with his remedy except those who die! How very droll.

Taylor

Precisely. We can't just hunt for Easter eggs that confirm what we already believe. The study is a masterpiece of scale, but as a strategist, I see some patterns that might be misleading because of how they adjusted the numbers. We really need to dig into the background here.

Holly

I agree. Understanding the history of where this data comes from makes it even more meaningful. These participants weren't just random people; they were health professionals who dedicated their lives to science. It gives the whole endeavor such a warm, sincere sense of purpose, don't you think?

Taylor

It really does. When you have seventy thousand women and forty thousand men consistently filling out surveys for thirty years, you are looking at an incredible level of human commitment. It allows us to see the long-term impact of lifestyle choices in a way that a short trial never could.

Holly

It is almost like a long-form story where we get to see the ending. The study suggests that if you want to optimize your healthspan, you should focus on being as fit and strong as possible. It is a simple message, yet it carries so much weight for our future.

Taylor

And that is the core of it. Variety might be the secret sauce, but the underlying goal is building that deep reservoir of health. We are going to look at why these specific groups of people were chosen and how their history shaped what we know about living longer today.

Taylor

To really understand this new study, we have to look at its ancestors. Most of this data comes from two legendary cohorts: the Nurses Health Study, which started in 1976, and the Health Professionals Follow-Up Study, which began in 1986. These are the crown jewels of Harvard’s research.

Holly

It is so fascinating that it all began with an interest in oral contraceptives. Dr. Frank Speizer wanted to know the long-term effects on women’s health. He chose nurses because they have the medical knowledge to provide incredibly accurate information. It was the first study of its kind.

Taylor

And then it just grew! By the time the second cohort launched in 1989, they were looking at diet, smoking, and exercise. It transitioned from a narrow medical study into this massive narrative about how every single choice we make in our twenties and thirties echoes for decades.

Holly

How absolutely wonderful to think about that continuity. The men joined the story in 1986 with the Health Professionals study. It included dentists, pharmacists, and even veterinarians. Researchers knew these professionals would be committed to the long-term process, providing data every two to four years.

Taylor

That commitment is why we have the 2008 Physical Activity Guidelines for Americans. Those rules didn't just appear out of thin air; they were built on the backs of these nurses and doctors reporting their jogging miles and vegetable intake. It is the definition of a strategic long game.

Holly

There is something so graceful about that collective effort. Over the years, the focus has shifted toward aging well. We are now looking at how to maintain cognitive function and quality of life as these participants enter their later years. It is about more than just surviving.

Taylor

That brings up the concept of biological resilience. We know that after the age of thirty, humans naturally start to lose about three to five percent of their muscle mass every single decade. If you aren't actively building a stockpile of resilience, you are essentially playing catch-up forever.

Holly

I remember our discussion on muscle banking. It is such a lovely metaphor. By exercising in our thirties, we are making a deposit into a health account that we can withdraw from later. It is especially vital for women, given the risks of osteoporosis and the changes of menopause.

Taylor

The statistics on this are quite sobering, actually. Seventy percent of people who suffer a hip fracture are women. And nearly a quarter of those who break a hip die within the year due to immobility complications. That is why building that muscle reserve early is a brilliant move.

Holly

It really emphasizes why the Harvard researchers were so keen on tracking variety. If you only do one thing, you might miss out on building the specific type of strength that prevents a fall. A mix of aerobic and resistance training seems to be the most sophisticated approach.

Taylor

The study also looked at diet quality, using something called the Modified Alternative Healthy Eating Index. They found that the most active people also had the healthiest diets. This is where it gets tricky for the statisticians. They have to separate the benefits of the broccoli from the benefits of the biking.

Holly

I suppose that is the challenge of observational science. You cannot just lock thousands of people in a room for thirty years and control their every move. You have to rely on their sincerity and then use complex math to try and find the truth amidst all that life.

Taylor

Exactly. This is what we call epidemiology. It is the study of patterns, but it is not a perfect experiment. Because the researchers aren't assigning people to exercise groups, they have to deal with confounding variables. For example, people with more money might have more time to exercise and better food.

Holly

So, they have to adjust the data to make it seem as though everyone had the same background. It sounds like a very delicate process. If you adjust too much, do you risk losing the very thing you are trying to measure? It seems like a difficult balance to strike.

Taylor

You hit the nail on the head. That is the exact tension in this new study. They adjusted for things like BMI and blood pressure. But since exercise naturally lowers those things, many critics argue that the researchers accidentally erased the very benefits they were looking for! It is a statistical paradox.

Holly

How curious! It is like trying to measure the beauty of a garden but then removing the flowers from the final count because they are a result of the gardening. It makes the whole idea of a plateau in exercise benefits seem a bit more questionable, doesn't it?

Taylor

It really does. When you look at the unadjusted data, the benefits of exercise don't plateau at all; they keep going up the more you do. It suggests that our capacity for health might be even higher than the official headlines suggest. There is no such thing as too much movement.

Holly

That is such an encouraging thought. It makes me want to go for an even longer walk this afternoon! I also find it interesting how the study has evolved into the third generation, NHS 3. It is now entirely web-based and includes men and women from all backgrounds.

Taylor

It is the democratization of data. They are now looking at environmental exposures and even adolescent diets. We are starting to see how the air we breathed as kids might interact with our exercise habits today. It is all one big, interconnected story of human health and longevity.

Holly

It is truly one of the most significant investigations ever conducted. To think that it all started with a simple question about health and has now become a guide for how we all live. It gives me a sense of wide-eyed wonder at the power of long-term science.

Taylor

And that history provides the context we need to look at the current conflicts. When experts disagree on these findings, they aren't just arguing about numbers; they are arguing about how we interpret thirty years of human lives. It is a high-stakes game of intellectual chess.

Holly

I am so looking forward to hearing about those disagreements. It is often in the tension between different viewpoints that we find the most sophisticated truths. Let’s dive into why some people are skeptical of these latest headlines and what the debate is all about.

Taylor

The conflict really boils down to how we prove cause and effect. In a perfect world, we would use randomized controlled trials for everything. But you can't randomly tell ten thousand people to run marathons for thirty years while another ten thousand sit on the couch. It is just impossible.

Holly

So we are left with these observational studies, and that is where the sparks begin to fly. It seems there is quite a debate about whether we can truly say exercise causes long life, or if it is just that healthy people happen to be the ones who enjoy exercising.

Taylor

This is the fundamental problem of causality. We can only observe one reality at a time. To get around this, researchers use statistical adjustment to create a kind of pseudoreality. They try to mimic what would have happened if everything else was equal, but critics say this is often a bridge too far.

Holly

I see. It is like trying to imagine a world where everyone has the same diet and the same stress levels, just to see the effect of a morning jog. But life is so much more tangled than that. Some experts believe we simply cannot infer causality without a strict intervention.

Taylor

Exactly. There is one camp that says if you didn't do a randomized trial, you don't have proof. Then there is the other camp, which I find much more interesting, that uses causal modeling and tools like Directed Acyclic Graphs, or DAGs, to map out these complex relationships.

Holly

DAGs sound so sophisticated! I imagine them like a map of all the different paths a life can take. You have arrows pointing from diet to health, and from exercise to weight, and trying to find where the real connections are amidst all those crossing lines. It is quite elegant.

Taylor

They use these maps to identify backdoor paths. A backdoor path is an indirect connection that creates a fake association. For example, if wealthy people exercise more and also have better healthcare, the healthcare is a backdoor path that might make exercise look more effective than it really is.

Holly

So the statisticians try to block those paths. But as you mentioned earlier, if they block a path that is actually part of the benefit, like blood pressure, they might be throwing the baby out with the bathwater. It is a very delicate, almost artistic, use of mathematics.

Taylor

Precisely. And this leads to a huge debate in meta-analysis too. Some people want one single, average number for how much exercise we need. Others say that is useless because the results vary so much between different studies. They want to know why the results are so messy.

Holly

It reminds me of the Science Vs podcast controversy. They claimed there was no controversy on certain topics, but critics pointed out that the studies they used were often small or had no control groups. It shows how even popular science can be a bit selective with the truth.

Taylor

That selectivity is a real danger. In the BMJ study, the researchers highlighted that variety is best. But if you look closely at their data, it might just be that the people who are already the healthiest are the ones capable of doing many different types of sports. It is reverse causation.

Holly

Oh, I see! It is not that variety makes you healthy, but that being healthy allows you to enjoy variety. How absolutely tricky! It makes one realize that we must look at these headlines with a touch of sophisticated simplicity and not just believe every graph we see.

Taylor

Even the jogging versus running data was strange. They defined jogging as slower than ten minutes per mile. But a ten-minute mile is a sprint for an eighty-year-old and a stroll for a twenty-year-old. When you use fixed definitions like that, the data starts to look like a W-shape or a U-shape.

Holly

A W-shaped curve for running sounds more like a zigzag than a clear path to health. It is a warning sign that the data is being chopped into pieces that are too small to be meaningful. We must be careful not to over-interpret these little squiggles in the statistics.

Taylor

The strategist in me says we should look for the signal in the noise. The signal here is that movement is good, but the specific details about whether swimming is better than cycling might just be statistical noise. We can't let the complexity of the math obscure the common sense.

Holly

It is a bit like listening to a grand orchestra. You don't want to get so focused on one slightly out-of-tune violin that you miss the entire symphony. The symphony here is that an active life is a longer life, regardless of the specific instruments we choose to play.

Taylor

That is a perfect analogy. The conflict is really about how we measure the music. Are we looking at the sheet music or the actual performance? As we look at the impact of this study, we have to decide which parts of the advice are actually worth changing our lives for.

Taylor

The real impact of a study like this isn't just in the academic journals; it is in how it changes our personal health strategy. We have to distinguish between things that are just associated with health and things that actually move the needle on our survival. It is about hard clinical events.

Holly

I love that phrase, moving the needle. It seems the most reliable way to extend our lives is to focus on the big pillars: stopping smoking, controlling blood pressure, and managing cholesterol. These have been proven by dozens of large trials to actually prevent strokes and heart failure.

Taylor

Exactly. A ten-point drop in systolic blood pressure can lower major cardiovascular events by twenty percent. That is a massive impact! Exercise is a huge part of that because it naturally helps with all those factors. It is like a multi-purpose tool for your cardiovascular system.

Holly

And the variety aspect we discussed is so lovely because it makes exercise more achievable. If we don't feel pressured to maximize our volume in just one sport, but instead find joy in different movements, we are much more likely to stay consistent over those thirty years.

Taylor

Consistency is the ultimate strategy. The study followed one hundred and ten thousand adults and found that even small doses count. It reframes exercise from a chore you have to maximize into a consistent, achievable part of your daily rhythm. It is about compressing morbidity.

Holly

Compressing morbidity, what a sophisticated way to put it! It means we are not just living longer, but we are staying healthy and independent for a larger portion of our lives. We are avoiding the frailty and dementia that can make those later years so difficult. It is wonderful.

Taylor

It also impacts how we view the 2025 wellness insights we saw earlier. Things like hot baths mimicking altitude training or beetroot juice for blood pressure are interesting, but they are the icing on the cake. The cake itself is the cardiorespiratory fitness and the strength we build.

Holly

It is true. Survival curves don't move because of a clever podcast or a pretty lab number. They move because millions of people make those quiet, plain interventions every day. Like wearing seatbelts or getting vaccinated. They are the simple, sincere acts that keep us here longer.

Taylor

The societal implication is huge. If we can encourage a culture of variety and consistent movement, we can reduce the burden of chronic disease across the entire population. It is about making the healthy choice the easy and enjoyable choice for everyone, not just athletes.

Holly

I find it so heartening. It suggests that improving our longevity is less about being an elite performer and more about being a curious mover. Trying new things, whether it is a dance class or a brisk walk in a new park, all adds value to our life's journey.

Taylor

But we must be wary of the monetization of longevity. A lot of social media content confuses a biological story with a proven intervention. Just because something sounds clever doesn't mean it will actually add years to your life. We have to stick to the evidence that truly moves the needle.

Holly

That is a very wise caution. We should focus on the interventions that have the strongest causal evidence. It gives us a clear sense of priority. We can enjoy the latest health trends, but we must never forget the foundational pillars that truly support our well-being.

Taylor

The impact of this Harvard study is that it reinforces those pillars while giving us a bit more freedom in how we build them. We don't have to be runners if we hate running. We can be walkers, swimmers, and weightlifters all at once. That is a very flexible strategy.

Holly

It makes the future feel so much more inviting. We are moving toward a world where we have better tools to measure our progress and more personalized ways to stay fit. I am so curious to see where these emerging developments will take us in the coming years.

Taylor

The future of longevity research is moving away from questionnaires and toward objective data. We are entering the era of the wearable accelerometer. These devices measure actual movement in three dimensions, giving us a much more accurate picture of how people really move throughout their day.

Holly

How absolutely fascinating! No more guessing how many minutes we spent jogging. These little devices will capture every step and every climb. It will provide such a clear, sincere record of our physical activity. I imagine it will revolutionize how we understand the link between movement and health.

Taylor

And we are seeing a shift toward using biomarkers like VO2 max and grip strength as the ultimate vital signs. Grip strength, in particular, is a brilliant proxy for overall muscle reserve and resilience. A five-kilogram drop in grip strength is linked to a much higher risk of cardiovascular events.

Holly

I have heard it called a vital sign of aging. It is not just about your hand power; it reflects your ability to recover from an illness or a fall. Improving something as simple as your dead-hang time could actually be a very sophisticated investment in your future health and energy.

Taylor

The goal is to get as fit and as strong as possible, following whatever plan works for you. Whether it is high-intensity bursts to fight cancer or building a muscle bank for your seventies, the future is all about proactive self-care. We are reclaiming agency over our own biological resilience.

Holly

It is a very empowering vision of the future. By focusing on these objective measures, we can move past the messy data of the past and into a more precise understanding of our own bodies. It is a journey toward a longer, more vibrant life for all of us.

Taylor

That brings us to the end of today's deep dive. The takeaway is simple: keep moving, keep it varied, and don't get lost in the statistical noise. Thank you for listening to this personalized episode of Goose Pod, Project. It has been a pleasure to share these insights with you.

Holly

It was truly a lovely discussion. I hope you feel inspired to explore new ways to move and strengthen your body. Thank you for spending your time with us on Goose Pod. We look forward to our next conversation. See you tomorrow.

This podcast analyzes a large study on exercise and longevity, highlighting the importance of variety in physical activity. While hitting a certain exercise threshold provides significant benefits, doing more may not increase lifespan. The discussion emphasizes building a strong health reserve through consistent, varied movement as a key strategy for a longer, healthier life.

Read original at Outside →

Published January 30, 2026 06:26AMPeople often complain—and rightly so—that the typical exercise science study involves a half-dozen male undergraduates who follow some sort of workout routine for a couple of weeks. So you can imagine the enthusiasm that greeted a recent BMJ Medicine study that followed 70,000 women and 40,000 men for over three decades, looking for links between the various types of physical activities they engaged in and how long they lived.

Finally, definitive answers to our questions!The study was very widely covered in the media and extensively discussed on social media. The main message, as highlighted in the accompanying press release from Harvard, where the researchers are based, is that doing a variety of different types of exercise is healthier than doing just one thing, regardless of how much you do.

But commenters were also fascinated by a series of colorful graphs plotting dose-response curves for individual types of exercise, purporting to show that walking is the best, jogging is good but not too much, swimming is no good at all, and so on. And more generally, the results even hint that beyond a relatively modest amount of weekly exercise, doing more of anything doesn’t help you.

It’s worth taking a closer look at these results (the paper is free to read online), because they convey some important lessons about what exercise does for us, what it doesn’t do, and why even massive, long-running studies can lead us astray if we don’t interpret them carefully. I’ll take a look at three key claims: that too much exercise is bad; that certain types of exercise are uniquely bad; and that doing a variety of exercises is best.

Is Too Much Exercise Bad?First, some background: the data in the new paper comes from two well-known cohorts: the Nurses’ Health Study and the Health Professionals Follow-Up Study. Participants periodically filled in questionnaires reporting how much time in a given week they spent doing various activities such as walking, running, cycling, swimming, playing tennis, or lifting weights.

That’s the only data the researchers had on physical activity: no details on whether you’re spending that time, say, dog-paddling in the shallow end with your toddler or swimming across lakes at top speed.The most basic finding is that exercise reduced the risk of premature death. In the graph below, the most important line is “all cause mortality,” which expresses your overall risk of premature death compared to someone who doesn’t exercise at all, as a function of how much you exercise:The more you exercise, the less likely you are to die early.

(Photo: Courtesy of BMJ Medicine.)That all-case mortality line drops sharply and then plateaus at roughly 0.7—that’s a 30 percent reduction in risk—beyond about 20 MET-hours per week of exercise.Note that this is not hours per week of exercise. A “metabolic equivalent of task,” or MET, is a measure of how hard exercise is relative to how much energy you burn when you’re just lying on the sofa.

For example, they estimate that walking takes 3 METs (triple your resting metabolism), so walking for 2 hours would burn 6 MET-hours of energy. That means 20 MET-hours a week is just under an hour a day of walking. Running, on the other hand, is assumed to take 12 METs, so 20 MET-hours is 100 minutes of running per week.

So the big question here is: Is it pointless to do more than 20 MET-hours per week? Various versions of this question have been debated for the last decade or so. One answer: if you enjoy it, knock yourself out. There’s no evidence here that higher levels of exercise are actually bad for you. And intuitively, it makes sense that you eventually reach a point of diminishing returns from exercise.

Personally, though, I’m not convinced that 20 MET-hours per week is a genuine threshold. There are a lot of potential issues with this sort of epidemiological study, where scientists can only observe without asking people to change their behavior. The most important one is the risk of confounding variables: people who exercise a lot tend to be different from people who don’t exercise a lot, and some of those factors—socioeconomic status, smoking, nutrition, and so on—will affect how long people live.

To combat this problem, statisticians “adjust” the results to effectively make it seem as though the subjects were identical in every respect except how much they exercise. For example, in this study, they adjusted the results to equalize diet healthiness based on a score called the Modified Alternative Healthy Eating Index.

They have to do this because the most active subjects had a significantly higher diet score than the least active subjects, and we don’t want to mistakenly attribute the longevity benefits of their healthy eating to exercise.But they also adjust other factors such as BMI, blood pressure, and cholesterol levels.

And here we run into a problem of circularity. Exercise lowers BMI, blood pressure, and cholesterol levels, so it’s not surprising that the most active subjects have lower scores in all these categories. But statistically equalizing these parameters effectively erases some of the benefits of exercise!

If it appears that exercise has no longevity benefits beyond 20 MET-hours per week, that’s in part because we’re leaving out any beneficial effects of lowering BMI, blood pressure, and cholesterol.(Side note: yes, many people would argue that exercise doesn’t lower BMI. Let’s leave that argument for another day.

I will merely note that the average BMIs in this study, by quintile from least to most active, are 26.4, 25.5, 25.0, 24.5, and 23.9.)What difference does this statistical adjustment make? Here’s what the relative risk of premature death looks like for five roughly equal groups divided up based on how much physical activity they reported.

The “adjusted” data corrects for ethnicity, family history of heart disease or cancer, BMI, smoking status, diet quality, blood pressure, cholesterol, and various other factors:The longevity benefits of exercise only seem to plateau if you “adjust” them for factors like BMI, cholesterol, and blood pressure.

(Photo: Alex Hutchinson, based on data from BMJ Medicine)In the adjusted data, the benefits of exercise seem to plateau for the fourth and fifth quintiles. In the unadjusted data, on the other hand, the benefits continue to increase. The gap between the two lines reflects, in part, the degree to which the adjusted results are underestimating the benefits of exercise.

This is why I’m not convinced that the benefits of exercise plateau beyond 20 MET-hours per week.Are Some Types of Exercise Uniquely Bad?Lots of previous epidemiological studies have shown that exercise, as a whole, promotes longevity. This one is so big that they have the statistical power to break down the results by individual activities.

They share the results for nine of these activities in the following graph:Activities like walking, running, bicycling, and swimming all seem to have different effects on longevity. (Photo: Courtesy BMJ Medicine)What jumps out is that all the curves are different. Walking produces a big, robust decrease in the risk of premature death (the “hazard ratio”) followed by a plateau.

Jogging has a U-shaped curve; running has more of a W shape. Wait, what? “Jogging,” it turns out, is classified as anything slower than ten minutes per mile, while “running” is faster than that. This is our first warning sign that something is amiss, since ten-minute miles are a very different form of exercise for a fit 30-year-old and a mostly sedentary 80-year-old.

Still, it’s odd that the curves have completely different shapes.From the researchers’ perspective, the main message here is the unsurprising fact that the curves aren’t straight lines—that is, that the benefits of adding more exercise to your routine depend on how much exercise you’re already doing.

On social media, on the other hand, there’s a lot more commentary on the specific shapes of individual curves. Why, for example, is a little bit of bicycling good, a medium amount bad, and a very large amount good again? You can (and many commenters did) come up with elaborate explanations about how the cardiovascular benefits of cycling interact with the risks of getting sideswiped by a truck to create this odd-shaped curve.

But this is clearly nonsense. What we have here is imperfect data fed into complex statistical adjustment algorithms and then chopped into pieces that are too small to yield meaningful insights.Some of the curves do look reasonable. Walking looks okay (with the caveat, again, that the plateau is probably an artifact of adjusting for things like cholesterol).

I like the running curve, which suggests that (counter to earlier claims) more is better up to very high amounts. But that’s not how it works: you can’t just pick the outcomes that make sense to you and assume they’re “correct” while ignoring the other ones. That’s like the famous quote from ancient Greek physician Galen (which I encountered most recently in David Epstein’s forthcoming book, Inside the Box): “All who drink of this remedy recover in a short time, except those whom it does not help, who all die.

”Is Variety the Spice of Workout Life?This brings us to the central message of the study: that doing a variety of different types of physical activity is better for you than an equivalent amount of just one activity. This claim passes the most important hurdle, which is that it makes sense. As the researchers point out, there’s solid evidence that aerobic exercise primarily increases cardiovascular fitness while resistance exercise primarily increases muscular strength.

Both strength and cardiovascular fitness have been associated with longevity, so we should assume that variety is good.To test this claim, the researchers assigned each subject a “variety score,” which basically involved adding up the number of types of exercise they reported doing consistently. The maximum score was 13.

The problem, of course, is that people who have a higher variety score probably do more exercise overall—so if they live longer, you can’t tell whether it’s variety or amount that helped. You need to look at both factors at once.Here’s a graph showing the risk of premature death for three groups (on the horizontal axis) who had low, medium, or high total amounts of physical activity.

Within each group, there’s a data point for people who had low, medium, or high exercise variety:No matter how much exercise you do, doing a variety of activities seems to improve health. (Photo: Courtesy BMJ Medicine)You can see that, within each group, going from low to high variety mostly seems to be helpful.

The effect is clearest for the group doing the most overall exercise, which makes intuitive sense. My guess is that this is a real effect, but in addition to the problems with statistical adjustment that I mentioned above, there’s also a risk here of reverse causation: people who are already healthy are the most likely to play a weekly game of pickleball and jog a few a times a week and hit the gym.

So what should we take from this study, or more generally from the large existing body of epidemiology with all its strengths (big numbers and long timeframes) and weaknesses (messy data and lack of randomization)? A useful thought experiment is to imagine your reaction if the results had been reversed.

If this study had suggested that even modest amounts of exercise are bad for you, or that exercise variety shortens your life, I simply wouldn’t have believed it. Since that’s the case, I shouldn’t put too much weight on the findings even where they agree with my preconceptions.Someday, improved wearable accelerometers are going to give us big data sets where we’ll have a much more accurate picture of how and how much people really exercise.

Until then, there’s a parallel body of epidemiological research that skips the messy process of asking people to guess how much of each activity they do. It involves objective measures of fitness. Instead of asking “How much do you jog?”, they measure your VO2 max; instead of asking “How much do you lift?

”, they measure your grip strength. Both of these parameters predict longer life, with no evidence of negative effects even at the highest level of fitness. If you’re looking to optimize both your lifespan and your healthspan, the advice remains simple: get as fit and as strong as possible, following whatever plan works for you.

---For more Sweat Science, sign up for the email newsletter and check out my new book The Explorer’s Gene: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map.

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