Reality Check: Skinny People Must Have Fast Metabolisms

Found this on 'doubly labelled' or 'heavy water' - In practice, for both practical and safety reasons, almost all recent applications of the "doubly labeled water" method use water labeled with the heavy, non-radioactive forms of the elements deuterium and oxygen-18 (O-18 or 18O), or deuterium oxide-18 (D218O).

Boom.

Nice beardage.

metabolism, like most things, can be trained, mine was ruined with anorexia, I know maintain on 3500-4000 calories a day

I don't imagine a change in body mass had anything to do with that? How much did you weigh then and how much do you weigh now?

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.

Age and LBM plays a role so it's pretty inaccurate, but it's not too bad as a really 'quick and dirty' method assuming you are in an 'average' BF%. The higher BF% you get, the less accurate it gets.

That's why you use a food scale, lol.

So maybe the question should be why it's easier for some people to control what they eat and why it's so much harder for others.

And this could be where genetics comes into play. I read a study recently that people who are very overweight or obese have a much greater instance of a genetic mutation that actually makes them feel hungry after eating, often leading them to overeat.

The study was a prompted by the fact that those who have weight loss surgery and lose weight very quickly can reverse this mutation. Children born to overweight women with the mutation often have the same mutation, but children born to the same woman after weight loss surgery do not. It's pretty interesting stuff.

Do you have a ref. to the study?

At the risk of getting slammed again, I fail to see how weight loss surgery would correct a genetic mutation.

It's important to note: If you truly have a "slow metabolism" ... then you most likely have an underactive thyroid, which would cause way more symptoms than JUST weight ...

Two things...

I've got a friend who's one of those "I eat and eat and never weigh more than 105" people...and I admit that when we go out to lunch or whatever she eats just as much as anyone else. But I have no idea what she eats or doesn't eat when I'm not around. I've always assumed that she just enjoys being the special skinny snowflake that everyone else wants to be, so she exaggerates her food consumption. The fact that she brings it up all the time is a good clue that it's something she enjoys talking about and makes her feel good to be an object of envy.

Second, I remember reading a study many years ago that determined that the vast majority of people of a slim to healthy weight practice what they called "chronic restrained eating". In other words, they were mindful of what they ate and in what portions. Myself, I weighed between 120 and 150 for most of my adult life (up until I was about 40 years old) and maintained that weight only through restricting food and exercising. It certainly wasn't effortless.

So maybe the question should be why it's easier for some people to control what they eat and why it's so much harder for others.

I don't know your friend, so I can't comment on what her motivation may be, and certainly some people do have that type of motivation (and I have known people like that, but they also believed it to be true that they ate so much because they never felt restricted).

But, just to understand a possible other side of it. I've always been small and slim. And I have experienced a lot of people making claims that I must never eat, I must have a very restrictive diet, I must have an ED, I was even accused of throwing my food up in a restaurant bathroom (I've never been bulimic and never forced myself to throw up in my life and definitely did not throw up that day and I hate throwing up), or I must never have any fun. Blah blah blah. Which, btw, all of that is insulting because I am healthy (mentally and physically), and I look healthy and fit (not sickly or underweight).

So, in those circumstances I know I have learned to preemptively defend myself, to make it clear, so no one gets any weird ideas (mostly on this website, and not usually much in real life, unless it appears to be an issue). And sometimes people will say I must be naturally slim and I go along with that because it's true that I always have been, so I have no comment on other people's weight struggles because it's none of my business, how could I know, it's not my experience. The reality is that I regulate my food intake well. I've always monitored my weight and using the mirror to do so, and I've never let it get above anything I felt uncomfortable with. But, I've also never gone on a low calorie diet as an adult (and I share that partly, so people know that level of restriction is not needed and also so people know I've never starved myself). I think there is a combination of factors. One is that I've always been very active with my fitness, and I am a dancer, and in addition to that I am generally a very active person in my day to day life. Sometimes I would eat a lot, but then I also would have times in which I was so busy and active I would miss meals. And I've always made sure to have portion control. Even though I want to eat more, I don't. I'm on here now, counting calories, and that is working great for me. So, obviously an awareness of calories is helpful to fitness goals. But, none of this means that I don't have fun or enjoy life. I enjoy life in many many ways. I also enjoy life in active ways and try to make choices that keep me active. I also eat treats and enjoy that. I just don't do that all the time. And also, I have heard people say that they like feeling full. I don't like feeling full. I don't like feeling hungry either. I like to feel fed.

And one other aspect is that while some people underestimate how much they eat, I also think sometimes people over-estimate how much they eat.

But, with that said, I only know what my own experience is. I know what I have done to manage my weight and fitness. But, it's no judgement on other people. I don't know what they need to do and how that differs and I don't know what their struggles are. And everyone has had various types of struggles, it's life.

Sometimes people make other people's weight and fitness habits a personal issue to them. But, really it's a personal issue to the individual's life and it's not really anyone else's business unless they are curious in a reasonably polite way. But, most people aren't walking around talking about how they stay slim, unless other people are commenting on it enough to cause them to feel they need to say something, and once it has been brought up enough the person may feel some defensiveness towards the people that bring it up. That's all.

P.S. I did not actually read the whole thread and don't really know what people are discussing (but I did watch the videos). These were just some thoughts I had and I had just kind of stumbled across that one thing.