We've all known people that can eat anything and never gain weight and when asked, they say "I just have a fast metabolism". But what does that mean? Is their body inefficient at absorbing calories, or is their lean muscle mass burning more calories than normal, or is it something else? If their body is metabolizing calories at a faster level than normal, wouldn't that lead to things like a higher body temp?
Thanks.
James
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08-16-2010, 09:13 AM #1
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What does "Fast Metabolism" mean?
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08-16-2010, 09:19 AM #2
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08-16-2010, 09:25 AM #3
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08-16-2010, 09:39 AM #4
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08-16-2010, 09:50 AM #5
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Yes, there are people who struggle to put on weight because they do have a fast metabolism due to overabundance of thyroid hormone.
The thyroid hormones thyroxine (T4) and triiodothyronine (T3) are responsible for regulation of metabolism of every cell in the body.
If you have an overabundance of these hormones (i.e. hyperthyroidism/overactive thyroid) then you will have increased BMR & heat generation, protein synthesis, bone growth, etc. These hormones regulate protein, fat, and carbohydrate metabolism, affecting how human cells use energetic compounds.
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08-16-2010, 09:52 AM #6
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08-16-2010, 10:06 AM #7
I read an article just yesterday talking about an experiment in which groups of people were overfed by 1k calories a day for I forgot how long and the weight gain at the end ranged from less than 1kg to almost 10 lbs.
The conclusion was that some people's bodies dramatically increased NEAT when overfed.
Were you the one who posted that link, by any chance?
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08-16-2010, 10:07 AM #8
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08-16-2010, 10:41 AM #9
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08-16-2010, 11:23 AM #10
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08-16-2010, 12:04 PM #11
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Wasn't me, but that sounds interesting. Would you mind posting the link?
That means that they don't know what they're talking about
Metabolism increases with total food energy (calories) consumed. The timing & frequency is irrelevant. Calories in vs. calories out. When you eat them is your preference.
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08-16-2010, 12:07 PM #12
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08-16-2010, 12:11 PM #13
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08-16-2010, 12:21 PM #14
Here it is; a research review actually.
http://www.bodyrecomposition.com/res...ch-review.html
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08-16-2010, 12:32 PM #15
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Thanks! It's funny that I can relate to both sides of the story...when I was cutting @ 1600 calories and no carbs, simply looking at a piece of bread would make me gain a pound. Once I got my metabolism back up, I'm sailing at 2800 calories. The energy balance equation always works...it's just that energy expenditure is extremely variable.
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08-16-2010, 01:44 PM #16
Those who've been designated with "fast metabolisms" usually have two things going for them, great appetite regulation and/or high NEAT. As mentioned, they don't eat as much as they think and if they do overeat, there appetite is suppressed for the rest of the day or even the day after and there physical activity increase via NEAT.
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08-16-2010, 01:57 PM #17
Metabolic rate can vary drastically from person to person. It all comes down to genetics, age, sex, body size, body fat vs lean muscle, your past history of dieting, how fit you are, hormones, etc. Indviduals with BMRs as low as under 1,000 a day are rare, but it does happen. Then there are individuals with BMRs aroud 4.000. It's rpetty comlicatd, but basically, a fast metabolism is when you have to eat a lot of calories in order to not lose weight.
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08-16-2010, 02:11 PM #18
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I haven't done much research on this....but I believe when someone gains a lot of weight and becomes obese, the total quantity of fat cells increases. However, even if weight is lost, the body does not get rid of most of them.
I used to be obese...so if the above holds true, then I have more fat cells than I would if I was always lean. This would correlate to an increased propensity to store fat than someone with identical body composition who was always lean. At the same time, it might work in favor of fat loss as well....
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08-16-2010, 02:25 PM #19
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This is what I haven't been able to understand yet.
Given a person that has to eat a lot of calories in order to not lose weight, and if energy in = energy out, what is the person's body doing with all those calories it's getting. It's not converting them to stored energy since, as you said, they are eating a lot just to maintain and not lose weight. So, are the calories just not being absorbed? Is that person's body temp a few degrees higher than normal due to the body converting it to heat?
Not trying to be a pain, just trying to understand....................
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08-16-2010, 02:38 PM #20
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08-16-2010, 02:43 PM #21
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08-16-2010, 02:44 PM #22
Basically, there are a zillion different processes going on in your body all the time, whether you're sleeping, sitting around, or working out. Cells "pump" stuff like ions and water between each other, they relsease hormones or take up hormones, they get rid of old unnecessary molecules and build new ones. All this microscopic stuff is going on all the time, and takes energy- i.e. it burns calories. In some people's bodies, there's either more of that going on, or it takes more energy to make it go on. In either case, they have a faster metaoblic rate.
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08-16-2010, 02:53 PM #23
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As we mentioned, it means that they have a higher metabolic rate (energy out). This means that each of their cells produces more energy (Na+/K+ -ATPase), and, in general, their bodies have increased turnover of different endogenous macromolecules because the speed of synthesis and degradation is increased. The rate of protein synthesis & degradation is increased, glycogen breakdown and glucose synthesis in gluconeogenesis is increased, breakdown of cholesterol and the number of LDL receptors are increased, lipolysis is accelerated, cardiac output by means of increased heart rate is increased, serotonin production by the brain is increased...etc. etc. etc. All these processes require energy. The faster they occur, the higher the metabolism, the higher the "energy out" and the more you have to eat to maintain weight.
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08-16-2010, 03:05 PM #24
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08-16-2010, 04:08 PM #25
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Thanks. Part of what was confusing me was the equations I've seen for calculating BMR. They don't seem to take into account anything other than weight, height, and age - for instance for men: (13.75 x w) + (5 x h) - (6.76 x a) + 66. But, I suspect that those constants would have to be adjusted for someone with a high metabolic rate.
I appreciate the help. I don't think my rep power of 0 is going to help you much, but the thought is there.
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08-16-2010, 04:29 PM #26
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08-16-2010, 05:26 PM #27
Miss my answer?
Also while BMR's can vary between people of the same weight, it's not that extreme and variance is somewhere around 15%, not enough to explain the genetically lean's resistance to fat gain.
Again, people's food intake and activity (exercise and/or NEAT) for the most part explain the so called fast metabolism.
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08-16-2010, 05:47 PM #28
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Don't mnd my ignorence but doesn't eating more meals a day (not "smaller meals" )keep your matabolism higher because you are constantly digesting therefor burning more calories than you would by eating every 5 hours or so? I am aware that it is calories in vs. calories out but i have been force fed the idea that many micro meals raise matabolism and I always thought because the total calories taken in would be the same (ie 1800 cals from 3 meals vs. 1800 cals from 6 meals) but the mini meals would be burning more calories at rest due to constantly digesting food from eating every 2-3 hours.
Inform me please :]"There is no such thing as over training, you can only under eat." - Jay Cutler
" Those are heavy weights, for a small woman." - Dorian Yates
2011 bodybuilding.com 100k transformation challenge runner up!
450/320/560 @205
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08-16-2010, 06:16 PM #29
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08-16-2010, 06:16 PM #30
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