Metabolism + aging

[highland145]

Always hear that it slows as we age. I've thought that was mostly due to life, family, job, etc. Of course, at some point, the body can't do what it did 20 years ago so there would be less activity and a slower metabolism. But if we do a lot physically shouldn't it stay high? Or, at least, higher than average. Asking because my nutritionist had me do a co2(?) test where I breathed into a machine for 10 min and it "calculated" my resting caloric rate. I'm 46 and the resting rate was 2170 cal/day.

Thanks.

 

[SociallyChallenged]

Always hear that it slows as we age. I've thought that was mostly due to life, family, job, etc. Of course, at some point, the body can't do what it did 20 years ago so there would be less activity and a slower metabolism. But if we do a lot physically shouldn't it stay high? Or, at least, higher than average. Asking because my nutritionist had me do a co2(?) test where I breathed into a machine for 10 min and it "calculated" my resting caloric rate. I'm 46 and the resting rate was 2170 cal/day.

Thanks.

Well, you're talking about two separate things. First of all, you're talking about basal or resting metabolism. As you age, resting metabolic rate (RMR) significantly decreases. What the nutritionist measured was your RMR. You also mention activity's effect on metabolism. Activity does not change basal metabolism. It does, however, modify overall caloric expenditure. Caloric expenditure is made of up three things: the thermic effect of activity, the thermic effect of feeding, and the resting metabolic rate. If you increase activity, you definitely increase total caloric expenditure. However, RMR is independent of activity levels. RMR and activity both act on calories burnt, but they are considered different things. RMR is your "metabolism" that slows with aging.

 

[highland145]

Well, you're talking about two separate things. First of all, you're talking about basal or resting metabolism. As you age, resting metabolic rate (RMR) significantly decreases. What the nutritionist measured was your RMR. You also mention activity's effect on metabolism. Activity does not change basal metabolism. It does, however, modify overall caloric expenditure. Caloric expenditure is made of up three things: the thermic effect of activity, the thermic effect of feeding, and the resting metabolic rate. If you increase activity, you definitely increase total caloric expenditure. However, RMR is independent of activity levels. RMR and activity both act on calories burnt, but they are considered different things. RMR is your "metabolism" that slows with aging.

Thanks SC. That bites. RMR drops as we get older, must do more cardio, the bodies ability to do more cardio drops because we're older. Break out the fat pants.

I assume the thermic effect of feeding is the calories the body uses to process food.

Any idea if the tests are close to right? My bro was ~2350/day. He works very hard and eats a ton of food, 6'1" 175lbs.

 

[PricklyPete]

While I'm not "old" (32), I do more cardio exercise then ever...and I expect to keep this up for a long time barring any major injuries.

 

[highland145]

While I'm not "old" (32), I do more cardio exercise then ever...and I expect to keep this up for a long time barring any major injuries.

When I was 32, I was in the best shape of my life. Then I got married, had a child and got slack until ~3 years ago. Back to ~40 min cardio/day. Luck to both of us on the injuries.

 

[SociallyChallenged]

Thanks SC. That bites. RMR drops as we get older, must do more cardio, the bodies ability to do more cardio drops because we're older. Break out the fat pants.

I assume the thermic effect of feeding is the calories the body uses to process food.

Any idea if the tests are close to right? My bro was ~2350/day. He works very hard and eats a ton of food, 6'1" 175lbs.

Well, you can do more cardio/be more active in general or you can eat more fiber, monounsaturated fats, protein, and complex carbohydrates. That should reduce your caloric intake a bit since it'll make you fuller sooner, enabling you to choose your activity levels. I know some people who think they have to work out for an hour every day to keep their weight off. In reality, they could just cut 300 extra calories by not eating two extra cookies.

To try to answer your question on the accuracy of those tests, they are relatively accurate, but are variable depending on acute factors (sleep, previous activity levels, eating). How tall are you and how much do you weigh? And how old is your brother? Without that info, those numbers sound reasonable.

 

[highland145]

Well, you can do more cardio/be more active in general or you can eat more fiber, monounsaturated fats, protein, and complex carbohydrates. That should reduce your caloric intake a bit since it'll make you fuller sooner, enabling you to choose your activity levels. I know some people who think they have to work out for an hour every day to keep their weight off. In reality, they could just cut 300 extra calories by not eating two extra cookies.

To try to answer your question on the accuracy of those tests, they are relatively accurate, but are variable depending on acute factors (sleep, previous activity levels, eating). How tall are you and how much do you weigh? And how old is your brother? Without that info, those numbers sound reasonable.

I could just cut the beer........nah.
6'1", 197lbs 46 yrs. Bro is 6'1" 175lbs 49yrs.

It's apparent that you know your stuff and enjoy helping others. Just wanted to say thanks.

 

[SociallyChallenged]

I could just cut the beer........nah.
6'1", 197lbs 46 yrs. Bro is 6'1" 175lbs 49yrs.

It's apparent that you know your stuff and enjoy helping others. Just wanted to say thanks.

It's interesting that he's older and smaller, but has a higher RMR. Either the testing state for you guys was slightly different, or you got the bummer genetics

And it's definitely no worries. I'm glad I can help.

 

[darkxshade]

What is it about age that slows RMR? Using myself for example, if my body composition[160lbs @ 11%bf] stays fixed over the years, I imagine a lb of muscle will still burn[at rest... not from activity] the same amount of calories as it did 10 years ago or does it? So I assume any drop in metabolism will have to come from bodily functions? Would you be able to break down the specifics of where the drop comes from?

 

[highland145]

It's interesting that he's older and smaller, but has a higher RMR. Either the testing state for you guys was slightly different, or you got the bummer genetics

And it's definitely no worries. I'm glad I can help.

He's a plumber and works his butt off. I sit on mine, what God intended, imo.

 

[SociallyChallenged]

What is it about age that slows RMR? Using myself for example, if my body composition[160lbs @ 11%bf] stays fixed over the years, I imagine a lb of muscle will still burn[at rest... not from activity] the same amount of calories as it did 10 years ago or does it? So I assume any drop in metabolism will have to come from bodily functions? Would you be able to break down the specifics of where the drop comes from?

Body composition does not stay fixed over the years though. Although you can slow muscle wasting through resistance training, it will still occur, just at a slower rate. So from 40 to 45, you may only increase your body fat by 1%, but maintain the same weight. That's a loss of 1.6lbs of muscle. Although it seems insignificant, it adds up over time. For those who do not participate in some sort of resistance training, the average amount of muscle lost is around 10kg from 20 to 60 years old and 10kg from 60 to 80 years old.

On top of this, genetic factors slow metabolism as well. It's a bit vague and I don't know the main cause of it, but there are so many mutations in one's DNA over a lifetime. My guess is that the genes and gene transcription aren't running at maximum capacity anymore.

 

[PricklyPete]

When I was 32, I was in the best shape of my life. Then I got married, had a child and got slack until ~3 years ago. Back to ~40 min cardio/day. Luck to both of us on the injuries.

I do have a feeling that kids will definitely make things difficult. I've been married now 3 years going on 4...and I'm in as good shape as ever. My wife was gone all of this month (just got back) and I have to say, it was hard keeping my workout schedule with just 2 dogs to take care of. It will be interesting. My wife is going to be a stay at home mom...but I have a feeling my time will still be strained.

 

[marvdmartian]

Genes and eating habits have something to do with it all. My Dad (R.I.P.) was 5'-10" tall, and probably around 165-175 his whole life.

One time, I was visiting Mom & Dad (they did the whole "snow bunny" thing after retirement), and Dad got up one morning, came out, stretched, and looked down at the little pooch belly he had, then exclaimed, "Boy, I'm getting FAT!!"

 

[tortoise]

Resistance is futile . . but Jack LaLanne eluded the grim reaper until age 96.

 

[Koing]

Good reading and info.

Koing