Wednesday, July 14, 2010

Max the METs

According to this study regular exercise does not entirely counteract the negative health effects of a sedentary lifestyle. There is an independent benefit from low-level activity throughout the day. That is, risk of heart problems is a function of two (exercise-related) parameters:

1. whether you work out
2. your baseline level of activity.

Remind me to do a few burpees in between every article or calculation! A treadmill in the office isn't a bad idea... :-)

NYTimes: ... In a study published in May in the journal Medicine and Science in Sports and Exercise, they reported that, to no one’s surprise, the men who sat the most had the greatest risk of heart problems. Men who spent more than 23 hours a week watching TV and sitting in their cars (as passengers or as drivers) had a 64 percent greater chance of dying from heart disease than those who sat for 11 hours a week or less. What was unexpected was that many of the men who sat long hours and developed heart problems also exercised. Quite a few of them said they did so regularly and led active lifestyles. The men worked out, then sat in cars and in front of televisions for hours, and their risk of heart disease soared, despite the exercise. Their workouts did not counteract the ill effects of sitting.

Most of us have heard that sitting is unhealthy. But many of us also have discounted the warnings, since we spend our lunch hours conscientiously visiting the gym. We consider ourselves sufficiently active. But then we drive back to the office, settle at our desks and sit for the rest of the day. We are, in a phrase adopted by physiologists, ‘‘active couch potatoes.’’

... adults spend more than nine hours a day in oxymoronic ‘‘sedentary activities.’’ For studies like these, scientists categorize activities by the number of METs they demand. A MET, or metabolic equivalent of task, is a measure of energy, with one MET being the amount of energy you burn lying down for one minute. Sedentary behaviors demand one to one and a half METs, or very little exertion.

Decades ago, before the advent of computers, plasma TVs and Roombas, people spent more time completing ‘‘light-intensity activities,’’ which require between one and a half and three METs. Most ‘‘home activities,’’ like mopping, cooking and changing light bulbs, demand between two and three METs. (One exception is ‘‘butchering animals,’’ a six-MET activity, according to a bogglingly comprehensive compilation from 2000 of the METs associated with different activities.) Nowadays, few of us accumulate much light-intensity activity. We’ve replaced those hours with sitting.

The physiological consequences are only slowly being untangled. In a number of recent animal studies, when rats or mice were not allowed to amble normally around in their cages, they rapidly developed unhealthy cellular changes in their muscles. The animals showed signs of insulin resistance and had higher levels of fatty acids in their blood. Scientists believe the changes are caused by a lack of muscular contractions. If you sit for long hours, you experience no ‘‘isometric contraction of the antigravity (postural) muscles,’’ according to an overview of the consequences of inactivity published this month in Exercise and Sports Sciences Reviews. Your muscles, unused for hours at a time, change in subtle fashion, and as a result, your risk for heart disease, diabetes and other diseases can rise.

Regular workout sessions do not appear to fully undo the effects of prolonged sitting. ...

One MET for a 180 pound male is just over 80 calories per hour, or about 2000 calories per day. Walking is 3-4 METs and doing light work is 1-3 METs. I guess that means on those long travel days I'm burning hundreds of extra calories by walking through airports, standing in line, and staying awake for 24 hours.


Shawn said...

I know you will find this interesting, as will many of your many readers:


Sam said...

How is it possible that in 2010 this ludicrous canard that exercise has anything to do with heart diseases is still entertained?

You want to avoid CVD (and the other diseases of civilization)? Eliminate omega-6/omega-3 imbalance - this means absolutely no vegetable oils. Eliminate all excess fructose - this means anything more than ~ 10g/day. Eliminate grains if possible - if not possible, soak, grind and ferment them in accordance with traditional cooking practices.

Exercise has absolutely nothing to do with health or weight control. And if anyone yammers on about the 2nd Law, I'm going to revoke your friggin' physics degrees. You can tell me about the 2nd Law when you can track all entropy flows in human metabolic processes. Metabolic processes have nothing to do with friggin' heat engines.

botti said...

***If you sit for long hours, you experience no ‘‘isometric contraction of the antigravity (postural) muscles,’’ ***

I could probably spend more time standing in my office (reading stuff, while the phone..).

steve hsu said...

It's been said that views on health and diet are closer to religious views than scientific ones, at least at current levels of understanding.

> Exercise has absolutely nothing to do with health or weight control.

How confident are you in this assertion? 95% 99%?

It's a strange coincidence that my (estimated) caloric intake more or less matches my (estimated) expenditure, and when I either up my exercise level at fixed intake, or cut intake at fixed exercise level, I tend to lose weight.

There may be a lot of variation from individual to individual, and there might be good and bad calories (I'm familiar with all the Taubes and paleo stuff), but at least for me the basic model of caloric accounting seems to work fairly well.

Sam said...

Since you're only giving me two choices, I'll take the 2-sigma... ;-)

You're exactly right about views on health and diet. In fact, I like both Taubes and the paleo folks, but the real issue is not macronutrient composition or even trying to eat a paleo food model - it's the chronic inflammatory state most Americans are in. And there is pretty clear biochemistry how excess/imbalanced PUFAs and excess fructose cause this.

Are you familiar with Art Ayer's Cooling Inflammation blog? He's a biochemist. I'd also suggest reading Peter at Hyperlipid who gets pretty deep into the biochemistry as well as tearing apart the various studies.

Shawn said...

Steve, I found a better burpees video :-)

steve hsu said...

Nice! I've seen her before. Barely safe for work, though :-)

botti said...

Just on the exercise theme, I signed up to John Eliot's 'overachievement' newsletter a few years ago. One contained some interesting recommendations about the importance of stretching:

" buried in the back pages of behavioral physiology journals: cats stretch between 150 and 250 times a day...

..flexibility highly correlates with core strength is well documented in the literature. The more limber you are, the stronger you are. Simple. Well known. Why people don’t follow through on that powerful piece of information… we’ll get back to that in a future newsletter. But of equal significance, though unfortunately less publicized, is the fact that stretching reduces incidence of a whole host of maladies including arthritis, osteoporosis, mobility decline, low energy, and yep, depression and low self-esteem...

Longitudinal data on cat behavior indicates that the feline species has low rates of all of the above aging complications. They tend to retain their strength, mobility, and energy through middle age much better than other species. Cats that do show these signs of aging, interestingly, have been observed to have a parallel reduction in their natural stretching frequency.

If you follow the science behind it, it is better for you to do a quick, 30-second stretch every time you stand up, switch activities, take a break, go to the cooler for a bottle of water, or have an attention shift. Not a major yoga routine, not a planned check box on your lengthy to-do list, but a functional, basic, feel-good stretch."

CW said...

Business Week also covered this topic recently, quoting some researchers in the field (Mayo Clinic, U. Missouri, UC Berkeley).

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