Reality Check: Skinny People Must Have Fast Metabolisms

I actually do have a problem with my metabolism. I'm in kidney failure and it's messed up most of my systems. The doctor said that I just can't break down and digest food very well. I don't use this as an excuse, however, because then I wouldn't get anyway. I just take it as motivation to work a little harder.

That's a legit medical reason, though. So many people say it's simply their metabolism when they're in perfectly good health, which is the problem that's being addressed here.

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Bumping to watch after work.

I remember that there was an Oprah show where she got her metabolism tested and it was actually higher then average ... I wonder whether it is actually portion size that catches people out, I mean I ate healthily, but 2-3 times the amount that I was supposed to :-)

I know this to be true for several people. They will delight in telling you how they only eat healthy foods and then proceed to eat 3-4 plates at every meal. Then they complain how they are not losing weight. Since most of the people are business clients I chew on my tongue and nod agreeingly with them.

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I've always had to eat much less than is recommended for a man of my height, weight and age if I want to lose weight. In the past, I have been guilty of blaming this on a "slow metabolism", but over time I've come to realise that it's more to do with HOW sedentary I am during a normal day - which is pretty much "completely sedentary"!.

Whether my metabolism is slower than normal or not is irrelevant - all that matters for me is that I have to eat less than I burn. That means I have to exercise a fair bit - I burn over 4000 calories a week - in order to give myself some extra calories to eat. If I don't do that, I have to eat so little that a diet is simply not sustainable over long periods of time.

For what it's worth, I am meticulous with my logging and weighing of my food (check my diary and you will see "2 Pringles" or "4 M&Ms" etc.) and by logging everything I eat and my weight loss, I know that my average TDEE works out at about 2200. If you take away the near 600 calories a day of exercise, that would give me a sedentary TDEE of less than 1700. This is MUCH less than the "average TDEE" which all the online predictions have, at somewhere around 2100-2200.

As I say, whether my TDEE is around 500 calories per day less than predicted is because I have a slower than average metabolism, because I sit on my *kitten* all day (when not exercising!) or whether (despite my care) I am very bad at measuring my intake, is immaterial - I have to eat what I have to eat and by doing that I know I can lose weight...

no no..bigger people have often better metabolism due to amount of food they eat, the only thing is they eat wrong food.

This statement makes no sense.

It makes perfect sense. Usually, the bigger you are the FASTER your metabolism because you are unfit, so your body has to work harder to move your mass around. As you lose weight, you become more efficient (your metabolism slows). If you lose muscle mass, you exacerbate the issue. It is a well known double-edged sword, that all other thing being equal, someone who was once fat will burn fewer calories than someone who's always been slim. The more weight you've lost, the slower your metabolism will become.

This is where muscle building comes in.


Edit: to point out that I mean the "bigger people have a better metabolism" part. By better, I assumed he meant "faster". The part about it just being about eating the wrong food is rubbish. Sorry to say, but it really is quantity, not quality, that counts in weight loss.

Yes, bigger people have higher TDEE as they have more to move - I would not call it 'better' as it depends on why they are big - but I was really referring to the latter part of the sentence. So no, it does not make sense.

Doubly Labelled Water throws it all out in the open. LOL :laugh:

How can you just "forget" about 43% of what you've eaten??

I don't think they necessarily forget, I just think people suck at estimating portions. Many many times you'll see threads here where someone says they're eating low calories and not losing weight, and then it turns out they aren't weighing/measuring, or they don't log weekends. Although, I do think it's possible to forget about little things like a handful of M&Ms from the candy jar, licking the bowl while baking, or snagging a few crackers on the way through the break room, etc. People are really good at self-deception. The results are similar to this study, which found that even dieticians under-report their intake.

http://www.ncbi.nlm.nih.gov/pubmed/12396160

Having watched someone (non-jokingly) scoop out a "1/2 cup" of ice cream that filled a pint glass...its more common than you may think...

Yes, depressingly true. Once I went to the trouble to actually weigh it, I discovered that 1/2 a cup of ice cream is nowhere near as much as I want it to be. :sad:

Tagging...

I actually do have a problem with my metabolism. I'm in kidney failure and it's messed up most of my systems. The doctor said that I just can't break down and digest food very well. I don't use this as an excuse, however, because then I wouldn't get anyway. I just take it as motivation to work a little harder.

If you can't break down and digest food very well, does that mean it's hard for you to gain weight?

I think the first problem with some of those who use the "slow metabolism" argument is that they often never bother to actually work out the numbers. They just say "I've got a slow metabolism" and leave it at that, blaming it for their weight gain while not figuring out what their metabolic rate is.

This is why, although it is controversial in some regards, I think it's worthwhile to introduce youth to the concept of determining their BMR and TDEE. While it's true that children play by a different set of rules as they grow and they would need to be informed in that regard, there is value in teaching them about the principles behind determining individual needs so that they're used to the idea by the time they stop growing.

All I know is that, when it came to discussing diets in health class, it basically stopped at defining the food groups, tossing a food pyramid in front of the student, and a quick demonstration of portion sizes. A brief head-nod to exercise was given during a different portion of the class, which was completely separate from the diet portion. There was never a discussion about things like BMR or TDEE.

If children can learn that while growing up, then they won't need to learn about it when they're an adult who has had "that moment" and is now tasked with trying to undo what may be decades of uninformed behaviors.

Metabolism does slow down with age, about 5-10% less per decade after the 25th birthday. However, this slowdown is easily counteracted by exercise.

This is the second issue I see with some who use the "slow metabolism" argument. They often seem to overestimate how much their metabolism slows down with age. Even with this 5-10% reduction, that means that my BMR (I'm just going to round it down to 2000 for now) would drop 100-200 calories by the time I turn 40. Then, my BMR of 1800 (assuming I slowed down at the higher 10% rate) would drop 180 calories down to 1620 when I reached 50. Over 20 years, that's only a drop of 380 calories which, as you said, can be counteracted by exercise.



Something came to my mind as I was reading through other responses:

I wonder what portion of the "slow metabolism" crowd is made up of second, third, fourth, etc children. I'm a second-born, and, when I was growing up, I don't recall recieving portions that were smaller than those of my older brother (I will need to ask my mother if she did anything). In the long run, it wasn't much of a problem because my weight was under control by the time my parents released me into the world as an adult and my diet became mine to control. But I do remember being the "husky" one early on, especially during the years when my brother was taller than I was. Perhaps that can be attributed to eating the same portion sizes my older, larger sibling.

BUMP to review when I have more time

I don't know the actual science behind it, but it makes sense. When I was 300lbs, I could burn 3000 calories a day doing literally nothing. Now, at 183, I have to bust my butt to hit 2750 calories burned a day. I assume that fitter, lighter bodies are more efficient.

I think you missed the point. Studies show BMR is mostly a function of lean mass, with very little dependence on fat mass. Adding muscle mass and EPOC effect will increase energy consumption during periods of rest, but I'm not aware of significant impact to metabolic efficiency, which is cellular/genetic (other than hormonal/thyroid/hypothalamus issues arising).

I'm guessing your 3000 cals/day number didn't come from a calorimetry measurement, and is probably not accurate at all.

People WANT that original statment to make sense, because it justifies their eating more. Just another fattie excuse.

This thread is on point. Props to everyone who has lost weight and improved their health. But don't minimize the efforts of people who have always maintained a healthy physique by invoking the fast vs. slow metabolism excuse. It's insulting to those of us who have worked hard for many years (or all our lives) to stay fit.

I wasn't invoking it as an excuse, quite the opposite. It is far more difficult for me now to lose weight than it was when I was heavier. I know that Maintenance will be tougher still, unless I increase my lean body mass. I am not a special snowflake, but like I said, I don't know the science, but am definitely interested in learning exactly why this is.

Your BMR is actually higher the heavier you are. It takes effort for the body to 'do it's job' of keeping things working. The bigger you are, the more effort that takes. Fat is metabolically active, not as much as muscle, but still active, and everything has to work a bit harder and a bit more.

I don't know the actual science behind it, but it makes sense. When I was 300lbs, I could burn 3000 calories a day doing literally nothing. Now, at 183, I have to bust my butt to hit 2750 calories burned a day. I assume that fitter, lighter bodies are more efficient.

I think you missed the point. Studies show BMR is mostly a function of lean mass, with very little dependence on fat mass. Adding muscle mass and EPOC effect will increase energy consumption during periods of rest, but I'm not aware of significant impact to metabolic efficiency, which is cellular/genetic (other than hormonal/thyroid/hypothalamus issues arising).

I'm guessing your 3000 cals/day number didn't come from a calorimetry measurement, and is probably not accurate at all.

People WANT that original statment to make sense, because it justifies their eating more. Just another fattie excuse.

This thread is on point. Props to everyone who has lost weight and improved their health. But don't minimize the efforts of people who have always maintained a healthy physique by invoking the fast vs. slow metabolism excuse. It's insulting to those of us who have worked hard for many years (or all our lives) to stay fit.

I wasn't invoking it as an excuse, quite the opposite. It is far more difficult for me now to lose weight than it was when I was heavier. I know that Maintenance will be tougher still, unless I increase my lean body mass. I am not a special snowflake, but like I said, I don't know the science, but am definitely interested in learning exactly why this is.

Your BMR is actually higher the heavier you are. It takes effort for the body to 'do it's job' of keeping things working. The bigger you are, the more effort that takes. Fat is metabolically active, not as much as muscle, but still active, and everything has to work a bit harder and a bit more.

That's what I thought. Isn't there a "quick and dirty" way to estimate your BMR by multiplying your body weight by ten?
Edited for typo.

That's what I thought. Isn't there a "quick and dirty" way to estimate your BMR by multiplying your body weight by ten?
Edited for typo.

Not if you want an accurate estimate. Fat is not a significant contributor to BMR. Adding 100lbs of fat should only increase BMR maybe ~300 cals or so, not 1000 as your estimate would imply. If you care enough about your caloric intake to be logging food, you should find a better way to calculate your BMR.