It’s kind of a cliche that regular exercise is good for the heart. At the same time, I have been told that with fat people, the heart works harder because it has to pump more blood around. And that obese people have a tendency to have thicker heart muscles than they otherwise would have.
It seems that extra exercise is not automatically a positive thing.
Common sense says that the main difference between (1) the thin athlete ; and (2) the fat dude whose main exercise is stuffing his face with donuts, is that the athlete’s heart gets to rest and recover from the extra exercise it gets. Another possible difference is that the fat guy is likely to be eating foods which will clog up his arteries.
Of course, one can also look at anecdotal examples like Ron Daws, a world class distance runner who died at the age of 55 from a heart attack. Examples like this provide evidence for the “too much exercise” hypothesis.
So my question is this:
Why does the heart strain from regular, moderate exercise seem to be a lot better for your heart than the heart strain from being obese? If it is mainly the difference between constant and intermittent strain, is there any research to back this up? If so, what is the ideal amount of exercise for cardiovascular health?
Also, how much of a missing variable is diet? In other words, to what extent are fat people more likely to have heart attacks simply because their obesity is a proxy for eating a lot of junk food?
I just took up running and was told that the benefit actually comes from the recovery period. Get your heart rate up, then let it recover. Rince, repeat.
So perhaps the world class guy was pushing it too hard, and of course, the obese person is working it constantly as well.
The mystery isn’t why "extra work"of the heart in obesity isn’t beneficial but, rather, why the extra work of exercise isn’t a bad thing. Check out this article on the ‘Athlete’s Heart’.
In terms of comparing the heart of obese people to that of non-obese individuals, there is much more going on than differences in diet. Some of the additional variables include differences in blood pressure, blood fat levels, sleep disturbances, sex-hormone levels, and insulin levels (and insulin resistance/sensitivity), each of which can contribute to heart disease.
What you’ve been told is not necessarily true, although it is sometimes said. (Many details here.)
Still the easiest way to look at it is that the target is “cardiorespiratory fitness.” That’s the ability to adequately supply the working muscles during sustained increases in activity. “Exercise” is an increase above the resting state that increases the level of sustained activity that can be adequately sustained in the future.
To the degree that it may be true that an obese individual’s heart has a bigger load to supply at all times, rest and activity, and to some degree meets that load with greater baseline cardiac output (which again is not completely established that it occurs) that compensation does nothing to increase the goal of cardiorespiratory fitness since the same increase in demand is increased by even more during periods of sustained activity.
“Exercise” is not what you do at rest, whatever your at rest demand is. Your proposed obese individual working his/her heart at rest *is not exercising *and does not have high cardiorespiratory fitness due to high at rest demands. Conversely a person with high cardiorespiratory fitness from exercise (thin or heavy) will have a heart that does not need to work as hard at rest.
Yes, that’s very interesting. Just shooting from the hip, I would have guessed that significantly more exercise is optimal. Like 30-60 minutes a day, 5 to 7 days a week.
The general consensus, as reflected in the CDC’s guidance, remains that 2.5 hr/wk (150 min) of moderate intensity activity or greater is a good standard, but that less is still better than none and more gives more benefit albeit of diminishing returns. A sample of the other studies such a conclusion is based on here. (pdf) Prospective study of 416,175 individuals. Even 15 minutes a day gives benefit, largest benefit with the first 1 to 2 hours of moderate intensity exercise/week, vigorous intensity associates with greater mortality reduction. But continued mortality reduction with greater volumes in a curvilinear fashion.
I’m rather sedentary, so I have a personal trainer that I see twice a week for 1/2 hour sessions which consist of core and cardio. I also, have a treadmill at home, that I jump on, as soon as I get out of bed. And, I have a lot of stairs that I run up and down all day. With all that, I still don’t think I get 2.5 hours. Darn! I’ll have to amp it up.
I thought it was interesting that exercise seems to benefit women much more than men; for example, table 5 shows a relative risk of 0.81 for men and 0.61 for women, for 3,000 calories a week; this seems far to great to be explained by men needing to burn more calories (having a higher basal metabolic rate); the difference also increases as the calories burned increases.
ETA: Some Googling found this article which says the opposite - that women need to exercise more to have the same benefits, contradicting the above - at least for obese people with diabetes.
