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  #1  
Old 20 March 2012, 07:19 PM
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Icon07 Human Body Myths

“Old wives' tale”: The phrase conjures up notions of well-meaning old grandmothers boiling up plants and roots and rubbing lucky rabbits’ feet. But many of the things we believe -- and tell each other -- about the human body are passed on by intelligent friends, educated teachers and sometimes even doctors themselves. So arm yourself with these 10 facts, and whip them out next time your mother tries to force you into a warmer sweater.

http://ca.askmen.com/top_10/entertai...ody-myths.html
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  #2  
Old 20 March 2012, 07:40 PM
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This part seems wrong:
Quote:
The longer you starve yourself, the slower your metabolism will get, eventually resulting in a less efficient calorie-burning system. So skipping meals in the long run can actually make you gain weight.
If your metabolism became less efficient, then you would lose weight. A more efficient calorie-burning system will cause you to gain weight with the same amount of food. A less efficient one will cause you to lose weight with the same amount of food.
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Old 20 March 2012, 07:48 PM
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I think they mean less efficient (effective would probably be a better word) at burning calories, rather than less efficient in processes that require burning calories.

Not the best phrasing, but pretty sure that was their intent.
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Old 21 March 2012, 06:48 AM
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If your body burns calories less efficiently, doesn't that mean that fewer calories are extracted, and more calories are excreted as waste? So burning calories less efficiently means extracting fewer calories from the same amount of food.
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Old 21 March 2012, 08:24 AM
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Absorbing calories less effectively would mean that more were excreted as waste. Once you've absorbed them, they'd be stored as fat if you weren't burning them.

It's still backwards, though, whichever they mean. Even after you've absorbed the calories, a more efficient metabolism would mean you'd need to use less of the energy in your system to achieve whatever goal you were going for, and so more of it would be left as fat. A less efficient metabolism would mean you'd need to burn more fat to achieve the same goal.

The phrasing in the article is quite common and always annoys me for the same reason...
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Old 21 March 2012, 10:47 AM
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I tried to read the article, but between the page reloading every five seconds, waiting for the ads to load (slooowly) and the slideshow format of the article I just found it not worth the while.
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  #7  
Old 22 March 2012, 03:22 AM
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No. 1 is interesting. I've long suspected that, but educated people keep insisting late-night calories are somehow different (though I'm still waiting for a satisfactory explanation as to how).
I'm also skeptical about the idea of skipping meals leading to weight gain because your metabolism slows down. If your metabolism slows down when you're hungry, wouldn't it speed up when you eat a lot? I find it hard to believe your body would go into a long-term starvation mode just because you went maybe 14 hours without eating.
But then, I'm skeptical of the idea that the natural differences among different people's weights is the result of differing metabolic rates. I know I've told this story before: my best friend and I went vegan together a few years ago. We cooked many meals and often went out to eat together and shared everything, so our diets were very similar (except I was the only one who ever had seconds on dessert, and I drank more alcohol.) We also took dance together and generally just hung out a lot, so our lifestyles were very similar (except she had a much longer walk from her apartment to the subway station than I did, and she sometimes went to the gym while I went out and drank with my co-workers.) During the first month of our vegan diet, I lost a noticeable amount of weight--I don't own a scale, but my jeans were quite loose--but she gained several pounds. (She had been on a strict calorie-counting diet for years and had lost over 60 pounds; she had assumed she wouldn't need to do that anymore if she was eating vegan. I, on the other hand, had been working in a restaurant with a generous employee discount of which I took full advantage.) I would guess that, between my weight loss and her weight gain, there was at least a 10-15 lb. difference.
Even assuming some of it was water weight (again, though, why would she retain water while I didn't?), a pound of fat is about 3500 calories. There is no way in hell I was burning that many more calories than she was. Thirty sweaty minutes on the elliptical trainer only burns about 300 calories at most; I'd have to be doing the equivalent of 3-4 times that much more than my friend every day to account for a ten-pound difference over the course of a month. I doubt my body was using all those calories to make heat, either; I'd be burning up at that rate, and instead I'm a total wuss about the cold.
I think it makes more sense to figure that naturally slim people just don't absorb all the calories they consume. Maybe our bodies burn what they need, then store a certain amount beyond that--with different bodies having different numbers of fat cells--and then just let the rest go.
Anyone with an expertise in nutrition care to weigh in?
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Old 22 March 2012, 05:27 AM
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Quote:
Originally Posted by Esprise Me View Post
I think it makes more sense to figure that naturally slim people just don't absorb all the calories they consume.
People don't digest with 100% efficiency, you are right there. How much depends on the person, and the food. Some people digest certain types of food better than others. That is why when they track things like this they use a large group and take averages; people are very variable in processing and burning calories.

I have a very inefficient* metabolism/digestive system; I take in nearly 3000 calories to maintain my weight. If I want to gain, I have to get at least 3500 in. I know other people who maintain just fine at a little over half my maintenance intake. Some of it is surely absorption differences, but I don't think all of it is.

*As a side note, I also dislike the language reversal of more vs. less efficient metabolisms.
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Old 22 March 2012, 05:41 AM
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I don't have nutrition expertise, but the vast majority (something like 70% on average) of your caloric expenditure is "resting energy expenditure," and only about 15% is due to activity (although obviously this will vary based on how active you are).

So running on the treadmill only makes so much of a difference directly, but that doesn't in any way mean difference in metabolic rates does not have an important role in who gains weight and who does not. There can be bigger differences in metabolic expenditure between individuals than can be explained by differences in energy expenditure (and even counter to those differences)

And perhaps the biggest determinant of resting energy expenditure is lean body mass, which is increased by exercise. So someone who exercises a lot and has some more muscle will have a greater resting energy expenditure as well as the extra calories burned from exercise.


I also don't see how your anecdote counters the idea that differences in metabolic rate are important. It seems to me that you likely ate less than you were before and lost weight, whereas she maybe ate more and gained weight. Clearly what you eat has an impact on your change in weight, especially in the short run, but that doesn't by any means preclude an effect of changes in metabolic rate.

Your body is very good at maintaining a weight, and has many mechanisms to prevent long-term weight loss. This is thought to be a major reason why people who lose weight often gain it back within a few years. These mechanisms are persistant and losing 20 pounds doesn't reset what your body "thinks" is your normal weight instantly. Just speculation, but this could be part of the reason why your friend started regaining weight when she went off her strict diet - she's basically being pulled back to what her body still "thinks" is her baseline weight.

Last edited by Jahungo; 22 March 2012 at 05:46 AM.
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Old 22 March 2012, 06:46 AM
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Quote:
I also don't see how your anecdote counters the idea that differences in metabolic rate are important. It seems to me that you likely ate less than you were before and lost weight, whereas she maybe ate more and gained weight. Clearly what you eat has an impact on your change in weight, especially in the short run, but that doesn't by any means preclude an effect of changes in metabolic rate.
It's just that we started out about the same size, ate and exercised about the same amount, and yet her body obviously held onto much more than mine did. I don't know how my body could have actually used so many more calories; where did that energy go? Sure, we burn a lot sleeping and sitting around, but we both had 24 hours in the day. Sure, a lot goes to building muscles and the like, but I'm not a very muscular person; my friend and I have a similar build. And in my pre-vegan days, did my body really find a way to use an enormous order of mozzarella sticks and four beers while I sat in a booth for a few hours after work--and after a big dinner? Or is there another reason I never got fat?

Not trying to attack you, just genuinely curious and confused.
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Old 22 March 2012, 07:02 AM
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A lot of the energy goes into you being you; breathing, digestion, production of all the various fluids and goo that keeps you going. Some of it was just wasted. Some of it dissipates as heat energy. If you have different sized bodies, it will take different amounts of fuel to run them.

It is also probable that you don't absorb calories quite as easily as your friend. Either way, if you count it all as "metabolism", people do have different efficiency levels. I think most people do count it all as metabolism, and don't make a distinction between absorbing and burning.
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  #12  
Old 22 March 2012, 12:50 PM
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Quote:
Originally Posted by Esprise Me View Post
No. 1 is interesting. I've long suspected that, but educated people keep insisting late-night calories are somehow different (though I'm still waiting for a satisfactory explanation as to how).
Here's the one from my nutrition professor. I was in college some time ago, but here it is.

Late-night calories are not, in an of themselves, different. But your body, studies have shown, does what it can with calories you eat during the day, to keep your weight from changing. Or at least, it does for most people. So if people in the study were fed extra calories, observation shows they move more without thinking about it--office workers, for example, would start to pace while on the phone, whereas before they'd be sitting at their desks. And if fed fewer calories, they were less inclined to exert extra energy. Also, studies have shown that if you eat a really big breakfast, you will naturally be inclined to eat less at other meals. But your last meal is your last shot--if you eat a lot then, there's nowhere to take from to make up for it.

People don't sleep rougher--they don't start flailing around and kicking when overfed. Also, the body doesn't seem to "recognize" yesterday's calories. It's like every day it resets. So the calories you eat at night, apparently, your body is more likely to turn into stored fat (if it's extra).

That's what I was taught.
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  #13  
Old 22 March 2012, 01:40 PM
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Quote:
Originally Posted by Esprise Me View Post
(She had been on a strict calorie-counting diet for years and had lost over 60 pounds; she had assumed she wouldn't need to do that anymore if she was eating vegan.
As my doctor told me when I first started seeing him: "I don't know if you're a vegetarian or planning to become one to lose weight, but don't think vegetarians somehow all become skinny; I've seen [professionally] plenty of fat vegetarians."
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Old 22 March 2012, 01:59 PM
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I'm a vegetarian and I'm obese. Plenty of yummy fattening foods don't contain meat, especially if you're lacto-ovo rather than vegan (not that being vegan guarantees you won't get fat, either).
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Old 23 March 2012, 01:45 AM
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I had a friend who was vegetarian but weighed 250 pounds. For him "vegetarian" was not synonymous with "healthy". He ate a lot of fatty, salty, sugary, and overly-processed foods...he just didn't eat any meat.
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Old 23 March 2012, 12:49 PM
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There's really no reason to assume that "vegetarian" is synonomous with healthful eating. The presence of meat in someone's diet doesn't automatically mean they eat unhealtfully, either.

ETA: And of course this goes beyond whether someone is thin or fat, too. I worked with a woman who was vegan, and her lunch every day was a can of green beans. I don't know what she ate the rest of the time, but if canned vegetables did dominate her diet, she wasn't eating particularly healthfully. She ate a lot of chips, too.
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