fitness · Science

Is marathon running good or bad for hearts? And whose? And how? Science doesn’t know yet.

Newspaper reporters just love lurking around medical conferences, or so it would seem. Not willing to wait for papers to come out in journals, peer-reviewed and edited over time, journalists are showing up incognito at ballrooms of large hotels, consulting schedules, jotting notes and taking names.

The thing is, though: just because some group of researchers gives a talk with a particular result, that doesn’t mean that result is true, or applicable, or important or generalizable. Sometimes it takes a while to figure out what’s going on; there’s often a period in which different studies yield conflicting results. That’s common in real science. It may take a while for a more accurate picture to come out.

And so it is with a recent study about the relationship between endurance sports and what’s called “vascular age” — something to do with stiffness of arteries, which is bad, and an indicator of greater risk for vascular disease. If that wasn’t helpful, maybe this graph will clear things up:

Tables on how to derive one's vascular age. Easy-peasy, right?
Tables on how to derive one’s vascular age. Easy-peasy, right?

You might think that running marathons would be good for your arteries (I don’t know why; uh, why not?). Way back in January, a study came out saying just that.

According to a new study … researchers found that training for and completing a marathon, even at relatively low intensity levels, was associated with reversing age-related stiffening of the body’s main artery, the aorta, and helped to reduce blood pressure.

… researchers tracked 138 untrained and healthy first-time marathon runners over the course of a six-month period ahead of the 2016 and 2017 London marathons, including two weeks post-marathon….

The results found that for first-time long distance runners, training and completion of the marathon was associated with reductions in their blood pressure and aortic stiffening — which is when the arterial wall begin to fray due to stress.

Older, slower male marathons saw the most improvement. Researchers noted that while they only recruited healthy participants for the study, “those with hypertension and stiffer arteries might be expected to have an even greater cardiovascular response to exercise training.”

Well okay then. I’m happy for all those first-time marathoners. You go with your non-stiff arteries!

But wait– 5 months later, the news turned grim, at least for male marathon runners. According to another group of researchers, endurance sports like marathon running can increase vascular age by up to 10 years for men. But for women who ran marathons, their vascular age improved. Here are the deets, from a news article published this week:

Running marathons could age men by as much as a decade, research suggests... The study of males aged 40 and over who had taken part in at least 10 endurance events, found that their major arteries were far stiffer than would be expected for that age group.

However, the study of more than 300 regular athletes found the health of women who took part in endurance events improved. Female athletes had a vascular age around the same as their actual age and, by one particular measure, their vascular age was six years younger than their true age.

Scientists said the study… could not explain why the impacts of such events differed between men and women.

Okay, so some researchers gave a talk at a conference with some preliminary results that they can’t explain. Fair enough; this is legit practice at conferences. But I wouldn’t consider it news, much less important news, much much less worthy of the headline “Running marathons could age men over 40 by a decade”. Nope.

Sometimes, in fact most of the time, we need to wait for science to do more work and reach a solid consensus about what’s going on and why and for whom. this is one of those times.

While you’re waiting, it seems okay to rely on existing standard health advice, which is that exercise is good in many ways for us. More than that I shouldn’t say, lest some reporter is lurking around the corner…

You never know who's listening in from around the corner... picture of Mr. Bean behind a brick wall.
You never know who’s listening in from around the corner…

fitness · Science

Surprising new research on human metabolism: overview and some questions

CW: brief discussion of weight-blaming and shaming of people over 40.

Ah, conventional wisdom! We rely on it, use it to advise and direct other people, and conveniently forget times it doesn’t work for us. I decided to look up some good examples of conventional wisdom that are clearly not wisdom (in fact not even knowledge, as they’re arguably false). Here are some:

You get what you pay for.

One financial site pointed out that, in many circumstances, we get what we don’t pay for. That is, paying for something is a loss for us, and paying more is a greater loss. We have to pay close attention when paying more to determine if it’s a good deal. Hmmm…. Good thinking.

Warren Buffet, famous rich money-making person agrees, saying “price is what you pay. Value is what you get”.

If you can’t stand the heat, get out of the kitchen.

This saying suggests we have two options when things get difficult: push on through, or abandon our plans. No– I don’t think so. Informal logic classifies this as a bona-fide fallacy: the fallacy of false dilemma. When faced with a crisis or barrier, there are almost never only two options. We can slow down, enlist others, shift timelines, take a break and regroup, recast the parameters of the project… I could go on.

Here’s great advice on what to do if you’ve got too much heat/spice in food: add acid, veggies, nuts, broth, dairy, sweet or just make more. No need to leave the dish.

At last, we get to human metabolism and aging. Here’s the conventional wisdom:

No matter what we do, our metabolisms slow down over time, especially after age 40.

According to this view, our metabolisms slow gradually as we age and we experience a marked and continued slowdown of resting metabolic rate (insert all kinds of asterisks here, as this is super-complicated, and the conventional wisdom often conflates lots of distinct metabolic processes). In addition, there’s also conventional wisdom about ways we have control over our metabolisms.

Okay, if the convention wisdom about slow but inexorable decline in human metabolism is wrong, then what is right?

Short answer: we’re a long way from knowing in great detail how human metabolism works, and applying that to clinical medical and health practice.

Longer answer: a new study, combining very high-quality data on more than 6500 subjects from more than 40 testing sites, suggests a new four-stage model of human metabolism over the life trajectory. Veteran NY Times science write Gina Kolata sums it up here:

  • There’s infancy, up until age 1, when calorie burning is at its peak, accelerating until it is 50 percent above the adult rate.
  • Then, from age 1 to about age 20, metabolism gradually slows by about 3 percent a year.
  • From age 20 to 60, it holds steady.
  • And, after age 60, it declines by about 0.7 percent a year.

For those of you who prefer graphs, the original paper explains it below:

Graph of metabolism over the life span, showing sharp increase in energy expenditure through childhood, sharp drop in adolescence, plateau to age 60, then decline.

Here’s another conventional wisdom-buster from the paper that Kolata reports:

Once the researchers controlled for body size and the amount of muscle people have, they also found no differences between men and women.

But wait, there’s more myth-busting:

The four periods of metabolic life depicted in the new paper show “there isn’t a constant rate of energy expenditure per pound,” Dr. Redman noted. The rate depends on age. That runs counter to the longstanding assumptions she and others in nutrition science held.

Wow. So it’s not “calories in, calories out”, right? Right. That piece of conventional wisdom has been on its way out for a while now, and these results further explain the ways that view is wrong.


I have questions.

Media outlets are already using the results of this study to blame people over 40 for weighing more than they did when they were younger. From the BBC to beauty spas, the message is being put out there: increases in body weight after 40 aren’t because of slowing metabolism. Now insert implicit conclusion: it’s your/my/our own fault!

This was NOT one of the conclusions that came to mind for me. On the contrary: this study brings up lots of questions about the relationships among energy intake/expenditure, aging, activity, physical performance, cognition and mental acuity, and what’s in our future, given a better understanding of how the human machine runs over time. Two things I’d like to know:

How does the metabolism life trajectory graph look when it’s divided into weight groups? When it’s divided into other demographic groups?

We know there are many social determinants of health: that is, our environments and social/political/economic circumstances influence how long and how well we live. What effects do they have on the metabolic pathways over time?

One thing I believe firmly in and would promote as a piece of relatively new conventional wisdom is this:

Biology isn’t destiny.

We’re still very busy trying to figure out how the puzzle pieces of genetics, environment, behaviors, culture and community, economics, and justice (or lack thereof) fit together to predict, explain and promote human flourishing. This study gives a clear direction for new metabolic research. The puzzle, however, is far from completed.

Readers, did you hear about this in news or did you read the article? Did it strike you as good news? Did it change your views? I’d love to hear from you.

body image · fat · health · Science

Does my life depend on my body shape?

CW: discussion of body shapes and body weight, primarily with respect to a recent study assessing those variations in relationship to mortality risk. Lots of critique, too– you can count on that.

I have wide hips, large thighs and a large butt. Always have, always will. Regardless of my age, height, weight, fitness, that’s what my physical outline has looked like. My sister has always had slimmer thighs and butt, carrying more weight in her midsection. We are both in our 50s now, heavier and both carrying more weight in our midsections. We’re both doing what we do, happy to hang out when one of us can travel to the other.

My sister Elizabeth (left) and me, on the beach in South Carolina.
My sister Elizabeth (left) and me, on the beach in South Carolina.

All this is to say: we have the bodies we have, in the shapes they are. And even though the internet will offer you plenty of opportunities to spend your hard-earned cash on pills, supplements, gadgets and programs to try to change your body shape, I recommend saving it. It’s a waste of money.

So why do people worry about their body shapes and want to change them? In addition to all the messaging we get about what the “perfect” body shape is, medical science warns us of the dangers supposedly hidden in those shapes.

A new study came out in the past 10 days, looking at associations between body shape and mortality risk. Naturally, the press was on the scene, ready to inform us in the most provocative ways they could think of. Here’s a sample of the (inaccurate) headlines:

Headlines, the best of which is "thick thighs save lives". I wish this were the case.
Headlines, the best of which is “thick thighs save lives”. I wish this were the case.

What’s inaccurate about them? It’s not the case that having (or working to acquire) thick or chunky or wide hips and thighs will itself cause increased longevity; of course we know that. What these news outlets are saying is that people who carry their weight more centrally are at higher mortality risk than those who carry their weight less centrally. But is this true? Let’s see what the article is saying.

In a recent meta-analysis (study of a lot of studies) a team of Iranian and Canadian researchers set out to identify and quantify mortality risk factors specifically related to body dimensions and ratios Waist circumference, waist-to-hip ratio are commonly studied measures for this type of research. In addition, this group studied thigh circumference, hip circumference, something called “body adiposity index” (roughly, a function of the ration of hip circumference to height) and another fancy biometric called “A body shape index”.

In case you’re still reading (one can hope), here’s what the researchers concluded:

Indices of central fatness … were positively and significantly associated with a higher all cause mortality risk.

Larger hip circumference and thigh circumference were associated with a lower risk.

The results suggest that measures of central adiposity could be used with body mass index as a supplementary approach to determine the risk of premature death.

What do I make of this? Well, glad you asked. Here are a few takeaways:

One thing: They definitely found lower mortality risk associated with larger hip circumference. But there’s more– look at this pair of graphs:

Two graphs measuring changes in mortality risk as hip circumference increases.

What’s interesting to me here is that the top graph, which controls for BMI and waist circumference, shows the risk dropping well below 1 (which is set as the standard, so less than 1 is better). But in addition, the bottom graph, which doesn’t control for BMI/waist circumference, still shows a dip in the mortality risk below 1 up to about 112 cm, and a very small increased risk up to 120 cm.

Why is this interesting? Because the second graph shows that people with larger hips have a lower relative mortality risk, even apart from body weight.

Another thing: Here’s another set of interesting-to-me graphs:

Two graphs with mortality risk based on waist-to-height ratio for men (on left) and women (on right).

What we see here that caught my eye was how the waist-to-height ratio increase is fairly straightforwardly associated with increased mortality risk for men, but for women this is not so. As waist-to-height ratio increases, there is a dip in mortality risk for women before increased starting at around .52.

Which leads me to yet-another-thing: the researchers mention (which other researchers know but sadly, not reporters) that many of these associations disappear with age. That is, for people older than 60, these body dimension metrics and ratios don’t tell us much of anything about mortality risk.

Last thing: all through the text of this article, the authors either cite other studies or give results which suggest that body weight itself is not positively associated with increased mortality risk. They point out the need for studying different populations, including those who are healthy (vs. those with underlying medical conditions), smokers, ex-smokers, and never-smokers, and subcategories of those with men vs. women. What does this tell us?

Science is complicated.

A woman looking at the contents of a beaker; photo by the National Cancer Institute, via Unsplash.

So, does my life depend on my body shape? No.We have the shapes we do. Hundreds of features of both our bodies and the world our bodies inhabit influence how we live and how long that will be.

But I still kind of want this T shirt:

Thick thighs save lives.
Thick thighs save lives.

Readers: does this sort of body-shape research bother you? Do you ignore it? I’m curious about how these murky medical messages translate in the public. If you have any thoughts, I’d love to hear them.