More Sitting, More Diabetes: New Meta-Analysis

The first evidence linking exercise and health was a study of London bus workers in the 1950s. The drivers, who sat all day, had more heart attacks than the ticket takers on the same buses, who were on their feet all day. It was a huge advance — evidence, as opposed to speculation. The results were taken countless times to imply that exercise reduces heart attacks but epidemiologists understood there were dozens of differences between the two jobs. For example, driving is more stressful than ticket taking. Maybe stress causes heart attacks.

The first time I learned about this study, I focussed on two differences. The ticket takers were more exposed to morning sunlight (on the top deck of double-decker buses) and they were on their feet much more. Maybe both of those things — morning sunlight exposure and standing a lot — improve sleep. Maybe better sleep reduces heart attacks. The London data were not consistent with the claims of aerobic exercise advocates because the ticket takers did nothing resembling aerobic exercise.

Later I discovered that walking an hour/day normalized my fasting blood sugar levels — another effect of “exercise” (but not aerobic exercise). I had data from only one person (myself), but it was experimental data. The treatment difference between the two sets of data being compared (no walking versus walking) was much sharper, in contrast to most epidemiology. I am sure the correlation reflects cause and effect: Walking roughly an hour/day normalized my blood sugar. This wasn’t obvious. The first thing I tried to lower my fasting blood sugar levels was a low-carb diet, which didn’t work. I discovered the effect of long walks by accident.

A recent meta-analysis combined several surveys that measured the correlation of how much you sit with other health measures. The clearest correlation was with diabetes: People who sit more are more likely to get diabetes. Comparing the two extremes (most sitting with most standing), there was a doubling of risk. Because people who stand more walk more, this supports my self-experimental findings.

I found pure standing (no walking), or leisurely (on-off) walking, did not lower fasting blood sugar (which I measured in the morning). After I noticed that walking an hour lowered blood sugar, I tried slacking off: wandering through a store or a mall for an hour. This did not lower fasting blood sugar. I concluded it had to be close-to-nonstop walking. Someday epidemiologists will measure activity more precisely — with Fitbits, for example. I predict the potent part of standing will turn out to be continuous walking. Long before that, you can see for yourself.

 

 

 

 

 

 

 

 

 

 

9 Responses to “More Sitting, More Diabetes: New Meta-Analysis”

  1. jofx Says:

    I wonder if there’s any data on supermarket workers (shop floor vs checkout?). I worked in one for a few years and was incredibly unfit and ended up developing prediabetes, despite walking around (non-constantly) for the best part of 28-hours a week.

    It was funny how 5-minutes of light jogging practically knocked me out when I first attempted exercise, despite the “workout” I was getting from the job. HIIT helped turn me around, and you can find some studies that show the same kind of results, e.g. doubling the insulin sensitivity of a group of Iranian women in 12-weeks.

    Seth: I know of a study that found a correlation between jobs that required a lot of standing (such as supermarket checkout clerk) and MORE heart disease. That is, lots of standing in one place appeared to be bad for you. I agree about HIIT, that’s what I do.

  2. Celso Says:

    I’ve been leaning towards unsubscribing to your blog for a while, your writing has lost quality over the last few months. You have become too biased. Aerobic exercise has extremely positive effects on the body, and the way it functions, but you always depict it in a negative light. Either you hate aerobic exercising and should have a disclaimer whenever you mention the subject, or present data to the world that proves aerobics is not worth people’s time (good luck with that). Otherwise you’ll discredit everything else you write about, and that would be a shame.

    Thank you for the useful information on other subjects, I will no longer subscribe to you.

    Seth: Saying that non-aerobic exercise is good — which is what I say here — is not the same as saying aerobic exercise is bad.

  3. peter Says:

    i was concerned with post-meal blood sugar and found that a relatively short walk after a meal (i.e., 15- 20 minutes) lowed my blood sugar 2 hours after a meal from 148 to around 100. So i do this twice a day. I also take cinnamon (ceylon not cassia; the latter, i understand, may dangerously thin one’s blood)
    My recent recent blood test was well below 90.

    “While the two species of cinnamon share certain characteristics such as antimicrobial, and in terms of inhibiting the growth of fungi and yeast, and regulating blood sugar, their contents differ much in terms of the amount of coumarin, which is a naturally ocurring substance with strong blood-thinning properties. The coumarin level in Ceylon cinnamon is negligibly small, while that in Cassia cinnamon is an appalling 1200 times higher. The ingestion of large amount of coumarin or consumption of coumarin over a prolonged period of time can cause serious health damages and a negative impact on the liver and kidney. German FDA has warned against consuming the excessive intake of Cassia bark due to its coumarin content. ”

    Seth: Very interesting. Maybe my walking would be more effective if it were done right after meals.

  4. dearieme Says:

    How about two 15 minute cycling trips per day?

  5. Adam Says:

    @peter

    Congratulations & great job at taking responsibility for your health.

    In China they have a saying:“饭后百步走,活到九十九” which means “walk 100 steps after a meal & live to 99 years old”.

    Folk wisdom isn’t *always* useless.

  6. Txomin Says:

    Ticket takers also interact with an unusually high number of people.

  7. Javeux Says:

    Celso,

    I think the data on resistance training and HIIT in particular is evidence that aerobic enthusiasts may be wasting (a relative amount of) their time, at least if using that time efficiently to improve their health is their goal. I think exercise of almost any kind should be encouraged over sedentary lifestyles, but I just wish aerobics wasn’t the go-to solution for diabetics and others struggling with health problems, when there are much more effective, time-efficient alternatives that the general public seems oblivious to.

  8. charlie Says:

    How is vigorous walking for an hour non-stop NOT “aerobic” exercise?

    Celso is quite right. This blog is way too self absorbed. Goodbye.

    Seth: Who said it was “vigorous” walking? It is/was ordinary walking. I’ve done thousands of hours of aerobic exercise. There’s a big difference.

  9. Ashish Says:

    The Ikea JERKER line, discontinued but often available on Craigslist, includes a couple of excellent standing desk models. It’s by far the best thing I’ve done for my home office.

    Standing desks allow quite a bit of movement-in-place – it’s not the same as being, say, a cashier. And, I hope it goes without saying, you want to be barefoot when you stand.