Slow metabolism? Fast metabolism? How does it affect your calorie targets?

[Dulce9]

Hi all.  I just started a little weight loss group with some friends from work and wanted to make sure I'm giving good advice.  So we all know about the 500 calorie deficit from TDEE in order to lose a pound a week.  I've done that before and it worked.  But I also have a fast metabolism.  When I told my friends I was able to lose weight at 1600 calories per day, there was some surprise.  I think that they probably have lowered their metabolisms from unsuccessful dieting over the years.  

There's one big disadvantage to the fast metabolism thing--I normally consume a lot more calories than I should according to the TDEE.  So cutting 350 calories brings me to my TDEE and I don't lose any weight.  I have to have a deficit from the TDEE before I can lose.  So that level of calorie cutting feels like a huge shock.  It took me a long to figure out that I needed a larger deficit from my accustomed intake in order to lose.  

I'm curious about your experiences.  

[JuanFitbit]

Hi @Dulce9 , nice to see you around! Thank you for sharing the information. 

I agree with you that the metabolism is a big factor to loose/gain weight. 

But as with all the big changes on the body, everyone should get some advice from a medical or nutritional expert. They can figure out,  how the metabolism is for each one and the best steps to take to reach each goal. 

What you call as a disadvantage, with the fast metabolism, others might call it  luck. To be able to eat a lot of things without gaining weight. 

The metabolism is not only affected by the unsuccessful dieting over the years, but also from the fitness condition of everyone. 

Please keep sharing your thoughts and experiences, so others can have more info about it. 

See you around. 

[Heybales · Accepted solution]

If people are only comparing eating levels without all the other info - kind of useless frankly.

Metabolism is really just the BMR or RMR calorie burn for doing the most basic things the body needs.

A bigger body has to do more things, and younger body does more things, a taller body has bigger organs that burn a lot.

Calculated for vast majority are within 5% of true, even those with thyroid issues or no thyroid.

So your fast metabolism may mean extra 60-90 cal burn daily, slower people same amount less. In scheme of daily burn - metabolism differences aren't that big.

Then you have your NEAT - Non-Exercise Activity Thermogenesis - daily moving, fidgeting, ect.

A bigger body burns more being moved around.

This is where thyroid issues hit the body, being tired and not moving as much. This is where an extreme diet effects people. Extra 100 not eaten could easily have body adapt by not burning an extra 100.

TEF - Thermic Effect of Food - you burn calories to process the food you eat.

You eat more, you burn more, compared to eating less. So between people or even compared to diet and non-diet level yourself there are differences.

EA - Exercise - purposeful higher intensity type stuff usually for longer times.

Again bigger body burns more. Taller body with bigger organs burns more. Younger burns more. But small % of the total.

Yes people do effect their BMR by yo-yo dieting losing a little extra muscle each time, and getting older too harder to lose, and moving less usually.

Everyone has to have a deficit from their TDEE to lose fat weight.

Fast metabolism would mean your real TDEE is higher than calculated TDEE. Say 2200 to 2000.

Cut 350 calories from real you'd eat 1850 to lose weight.

Cut 350 from calculated you'd eat 1650 and still lose weight.

I explain that because your last paragraph doesn't make sense.

You are cutting 350 calories from what number from where, and getting to a TDEE that comes from where, and if that is TDEE of course you don't lose weight.

So yes friends could easily have lowered their metabolism from years of yo-yo dieting. Also it's impossible to compare like that unless you start including all physical stats, and activity levels, ect.

If a group of workmates are sitting around the table and different genders, ages, and sizes and wondering why they are either getting to eat different amounts or seeing different results eating the same amount (lets not even get into accuracy of food logging) - then they really don't have a clue on this, and at least should stop comparing.

[Dulce9]

Thank you, Juan.  It does get complicated, doesn't it?

[Dulce9]

Thank you Heybales for your extremely detailed answer.  I really appreciate it.  To add some numbers to this scenario, I calculated my TDEE to be about 2100 to 2150.  Fitbit also seemed to agree.  I was quite surprised to discover I consume about 2400 calories a day, sometimes more.  Yet I wasn't gaining weight.  When I first tried to lose weight, I cut about 300 calories a day but absolutely nothing happened.  No weight loss.  Finally I tried hard and got down to maybe 1700 or 1800 (with added moderate exercise), at which point I started reliably losing a half pound a week.  So I was wondering why my weight loss and gain wasn't exactly following the predicted course based on calorie intake.  At least I've figured out what it takes for me to lose weight--I would just like to understand it better.  

[Heybales]

So good numbers to keep track of. Numbers always makes it easy to change when needed without having to wait a long time, but even then.... as I'll explain.

But we always have to keep in mind the different between on-paper numbers (Fitbit included), and reality numbers.

If eating 2400 (it could be more or less literally due to inaccuracy but call it that) and weight not changing over a 4 week period - that is your TDEE then for whatever was your level of activity. Fitbit and TDEE calc are underestimating.

I say 4 weeks because even a 100 cal difference would take 35 days to slowly move a pound of fat, on or off.

A deficit of 300 is very reasonable (for a healthy body) and indeed should have shown a 1 lb drop after 12 days.

Problem is water weight fluctuations can easily be more than that and hide that change in scale weight.

If a woman your BMR literally changes through the month too, obviously water weight changes too, both make any weight logging under 30 days not really meaningful yet.

How long did you do that 2100 eating level and not see a change?

So when you went to 1700-1800 AND increased activity level you made the deficit even bigger - and side effect of exercise is usually water weight gain for several reasons, depending on what you do.

So that level appears to be a 250 cal deficit if a month long, again water weight changes can easily throw off figures.

Valid weigh-in to minimize known fluctuations would be morning after rest day eating normal sodium levels, not sore from last workout.

Anything other than valid just means you need more time to see a trend through the data noise.

Some people use a weight trend app and log every valid and invalid day. I like just valid days for good data points.

As to why it seems you dropped 300 and initially and no change?

Perhaps 2400 was actually above TDEE but small enough it would take awhile to see a change, as mentioned 35 days for 100 over.

So eating 300 less would really mean a 200 deficit, so now 18 days to slowly move a pound of fat, but again water weight could hide that fact.

Another potential reason - your body doesn't take the stress of undereating very well and starts adapting, even with say a minor 300 deficit if that is actual.

First thing a body does to lessen the deficit is stop spontaneous movements - fidgeting, leg tapping, ect, things the Fitbit would never notice.

Next level is just feeling tired, you perform more efficient movement, this may show as less steps if you don't have a goal and watch it and hit it.

Both have been shown in studies to occur at some point depending on how stressed your body is to the diet.

If body can't reduce the deficit to what it considers unstressful level with that, now less optional energy burn is attempted - keeping you warm, growing hair & nails as fast, replacing skin (it gets dry easier). 

After that is base metabolism of required functions slows down, and usually matches up with people eating so little there isn't enough nutrients - so now normal cell replacement slows down, usually eating so low not enough protein anyway so muscle isn't built back up (this is how most lose muscle in a diet - lot of energy to build it back, it requires a lot of energy to maintain, so body doesn't do either). This level is where women will lose their period.

300 real deficit could have caused the first to occur depending on your body and stress level, just less overall movement. I doubt you would go beyond this - unless you do recall it feeling harder to keep warm and putting on more clothes despite temps being the same indoors.

So now less deficit is really in place, Fitbit or TDEE calc would never know of this.

So now back to a long time span required to see actual movement on scale with normal water weight changes.

Has your food logging changed during any of that time - like getting more accurate?

Maybe it was a sloppy inaccurate 2400 originally or rough estimates, but a more accurate 1700-1800.

Like maybe eating out less, more weighing of foods, ect.

The end result of all this is usually the same, at what appears to be a small deficit - eat less, as you did.

Sadly it just means your numbers are off for some reason.

So as seasons change, activity level changes, just note the increase and know you can increase eating level by likely the same amount - though the number given won't be true for you, always an offset.

The reason I say small deficit - some take a large deficit and that stress can increase cortisol, can increase retained water slowly up to 20 lbs.

That will hide a lot of fat weight actually being lost, but the scale would never show it, or show it slower.

Life stresses, bad sleep, bad diet for nutrients, ect can cause this too.

In those cases eating even less just stresses the body harder - the body in that state will be doing some of those things referenced - not a great state for body to be in.

In those cases a refeed to get back to normal functions would be beneficial. Those are the people that say they ate 200 more calories daily for a bit, and dropped a bunch of weight suddenly. Stress water weight, probably became more energetic and moved more too, so now an actual bigger deficit than what they had.

It doesn't sound like you are the latter - but throwing it in there for context and others reading.

[Dulce9]

I really appreciate how you gave me so much food for thought.  I re-read your first answer a few times a few times, and one thought that came to mind is that any good experiment needs to be replicated, and perhaps there was something wrong with my numbers or my memory.  Another possibility I considered was that for some reason I wasn't absorbing some of the 2400 calories I was consuming.  My favorite non-dieting food is peanut butter, and I've read that some researchers believe not all the calories from peanut butter are processed.  There are many possibilities, as you point out.  Now that I'm covering the same dieting ground once again, I will watch the numbers and see if the weight loss follows the same path again.  If I notice anything interesting, I'll do a followup post.  So far it's too early to tell.  Thank you so much for your insightful answer!

[Heybales]

That is absolutely true about peanuts. So not the creamy PB, but crunchy. And Peanut M&M's (no one better think I'm advocating that), ect.

The fat you get in the PB oil still, no help there, but the peanut itself.

Like many fibers that in some countries the nutrition label counts those carb grams into the calories, but you really can't absorb them.

Now, in the scheme of a day and total calories - usually it's not that big a %. If someone had 50g of insoluble fiber per day, that's 200 calories not used. 

But it is also true a body without stress of undereating is much more inefficient. Don't absorb as much for a small aspect too.

It's nice having numbers you can trust, but there are always inaccuracies, and knowing how much to adjust quickly can be so useful.

[Dulce9]

Well, I went back into my Fitbit history to hunt for numbers.  I found one month in which I was very consistent about entering my calories as well as weight loss, and I have to say the numbers added up almost perfectly.  Fitbit said I was burning 2250 a day on average, while my calories averaged 1750 per day.  And I lost 4 pounds over that month.  So at least that seems to suggest that Fitbit's 2250 estimate is accurate.  Maybe peanut butter accounts for the discrepancy, since it is my favorite food when I'm not dieting.  Seriously, if not all those calories count, I'd like to know now so I can still include a little peanut butter in my diet.  Well, I do, but I still miss it.  I mix it with cottage cheese to lower the calories count.  Thank you again for all your help.  Perhaps I'll rely on Fitbit this time around for my burn estimate and see if that works out as predicted.  

[Heybales]

That is nice that in this regard you can be average enough the tool works nicely.

Or perhaps the inaccuracy on food side balances off inaccuracy on the burn side.

Anyway - numbers can be nice to review and confirm, and makes it easier going forward.

PB with cottage cheese. Hmmmm, used Hidden Valley Ranch mix before, not sure PB. Which I haven't had in a while frankly anyway, because I seem to need 2 PB & J sandwiches, can't do just 1. I wonder how long jam will keep in the fridge....

[Dulce9]

So I've now been back on this diet for a month, and the numbers are remarkably similar to my numbers from a couple years ago.  So that part is good. It's working.

But I'm still scratching my head about my pre-diet numbers.  Fitbit says I was burning about 2000 a day this winter.  And I know I was consuming a _minimum_ of 2400 calories a day.  It's the same conundrum as with my pre-diet numbers two years ago.  I'm pretty good with calorie counting, and of course hardly anyone _over_ estimates their intake, you know.  Sadly the error is always in the other direction.  

I was wondering what you think of "set points" or plateaus or whatever you want to call it, because that has been my best theory.  My body has gotten used to being this weight, therefore I can overeat a good bit and not gain and also eat a decent amount less and not lose.  I did this diet a couple years ago to prepare for a vacation.  After the vacation, naturally I eased up, especially because it felt like I was always starving.  I stayed hungry until I'd gained back all the weight, and then the constant hunger went away.

At one point in my life I managed to diet all the way down to my perfect and ideal weight, which was my pre-motherhood weight.  I know I hit at least one plateau on my way down where the diet quit "working" and I had to throw all my ammo at it.  One reason why I never go "all out" during the early phase of a diet--because I know I'll need more extreme effort at some point down the line.  

[Heybales]

As to differences in numbers.

It could easily be that in non-diet mode you burn more than Fitbit estimates - the numbers aren't good.

Be interesting to confirm that during next maintenance block.

But during a diet, when a body starts doing several things to reduce the daily burn - the Fitbit numbers start matching.

Good thing to be aware of.

You'll increase your calories when you reach goal, you'll reach Fitbit's estimated maintenance, and you'll likely experience some more slow weight loss it sounds like.

Of course that difference likely won't be as great when at a reduced weight.

There have been no studies that show any set points that prevent weight loss - but some hormones for sure change when fat is lost, making you more hungry, slowing body functions down because it's stressed.

What is changing is the estimated burn becomes wrong.

I'll post a synopsis below from my MFP blog on a study that showed just how bad that reduction can be depending on how foolish the diet is.

I will say your experience of more extreme down the line is likely because it was more extreme at the start than you thought - hence the body's reaction, hence your need to do even more. Several studies have shown reasonable all the way down is much more successful. A few recent studies have shown slightly more extreme than reasonable, mixed with frequent diet breaks, can be of great benefit in the long run.

The 5:2 diet shows that - eat at maintenance 5 days a week, eat at 25% of your maintenance on 2 days a week - results in 22% avg deficit, and 5 days a week of hormone reset.

Similar was diet a week or two, maintenance for a week.

Diet breaks for a week every 10 lbs loss have shown hormone recovery and body to keep progressing without stress.

Sadly unless in a study, you don't know your own line of when that stress happens - so we have averages of when that can occur, and better to be on the safe side, because once you go over it can take awhile to discover it, but it can then take awhile to get out of it.

Like vitamin or mineral deficiency can take a while to show signs until something finally becomes bad enough to get tested and discover. Some are left with life long effects if they waited to long, and it generally takes a while to get out of that problem state. Same with too much "calorie deficiency".

Here is study synopsis from about 9 yrs ago I wrote. Just shows how the body can adapt which is incredible. And incredibly annoying to attempting to use figures that are no longer true with reality.

------------------------------------------

Reduced metabolism & TDEE beyond expected from weight loss

So several studies have pointed to this effect of adaptive thermogenesis, some of which is expected. But found a nice recent one that covered several effects at once nicely.

First, the totally expected part. I'll try not to use the term metabolism as an all day type thing including all activities when that is really TDEE. Metabolism is mainly the lower level functions, some base and required though can be slowed down, some higher level functions like cell replacement for skin, hair, nail, muscle growth which can really be slowed down or skipped, and even higher level stuff like processing foods which probably shouldn't be considered metabolism normally, but some do ("kick start your metabolism by eating breakfast" misunderstanding).

Your TDEE is composed of your BMR (Basal metabolism) + NEAT (Non-Exercise activity) + TEF (energy burned processing food eaten) + EAT (Exercise activity).

If you eat less, your TEF burn (usually about 10% of what you eat) goes down, so TDEE goes down. So eating 2000 TEF is 200 of that, go to eating 1600 TEF is 160, so loss of 40 calories to TDEE, not much.

As you start to weigh less, NEAT and EAT (if pace & intensity kept the same) go down since you are moving less mass around, so TDEE goes down. What may happen though is you move more since you weigh less, and exercise harder. So perhaps no adjustment to TDEE, but probably lowering.

As there is less body mass for functions, the BMR will go down slightly. If mainly fat mass lost, not that bad since it didn't require much energy anyway (2 cal/lb a day). But muscle mass lost, while resting energy use isn't much (6 cal/lb a day), that lost muscle being used daily could impact TDEE badly. Along with less mass is perhaps less LBM which includes blood volume, less muscle is also less glucose stores (with water), and water management is a decent calorie burn too. So as weight goes down, BMR goes down somewhat depending on what is lost, and therefore TDEE will lower too.

So outside all those known and expected reasons for your metabolism and TDEE to burn less as you diet and lose weight, there is the one that could be avoided, and perhaps you want to avoid it to make maintenance easier.

And that is a drop in TDEE unrelated to any of the above, and is just the body getting more efficient with BMR, TEF, NEAT, and EAT altogether, metabolic adaptation is what it's usually called. Sometimes called metabolic damage, if you consider lower than what it was and could be damage, or merely the body doing what it has to do.

Here's the 6 month study in full if you want to dig in to it, I thought I'd point out some tidbits.

 http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004377

Participants had to be between BMI 25-30, overweight category, but healthy otherwise. They were excluded if they smoked, exercised more than twice a week, were pregnant, lactating or post-menopausal, had a history of obesity (BMI>32), diabetes, cardiovascular disease, eating disorders, psychological disorders, substance abuse or regularly used medications except for birth control. So that may have a bearing in comparison.

Diet was 55 / 15 / 30 for C / P / F. 

CR (Calorie Restriction) was 25% deficit from TDEE, so not massive.

CR + EX (EXercise) was 12.5% deficit plus 12.5% calories burned in cardio exercise 5 x week, each session being 403-569 calories for 45-53 min (women and men difference).

LCD (Low Calorie Diet) was 890 cal/day until 15% of weight was loss, then back to maintenance calories by month 3, whatever it was then. That's a tad massive

DEXA scans for body composition of LBM (Fat Free Mass (FFM)) and Fat Mass (FM). Sedentary TDEE measurements in a metabolic chamber for 23 hrs. SMR (Sleeping Metabolic Rate (BMR)) measured chunk of night no movement.

Several formulas related to measured Sedentary TDEE at baseline based on all available stats, to compare down the road when stats changed.

At 3 month check, sedentary TDEE had dropped by the following amounts, below what the formulas would have indicated for new measured LBM and FM, and SMR. In other words, it lowered the expected amount, and an additional...

CR - 371

CREX - 2

LCD -  496

At 6 month check, there was some recovery to be had, and reminder the LCD was at maintenance this entire time from 3-6 months...

CR - 209

CREX - 129 over expected

LCD -  275

So notice that even after 3 months maintenance level eating, the initial LCD group still had a TDEE 275 below what was expected for their current LBM and FM. Perhaps more time at maintenance it would have recovered?

The CR group slightly recovered, but still 209 lower than expected. 

The CR+EX group actually had an increased TDEE.

Now that was Sedentary TDEE in the lab that was measured and compared.

Daily TDEE with all activity was also compared to their SMR, TDEE/SMR for physical activity rate (PAR).

At month 3, CR and LCD had significant drops in PAR below what would have been expected for their current LBM and FM, by CR 350 and LCD 497, with CR-EX having none. At month 6, CR 215 and LCD 241, so again some recovery.

So the NEAT part of their day decreased as expected because of lower weight, but even more than expected because of less movement, resulting in lowered figures above.

So, that is how much their TDEE dropped along with their lower eating level and weight.

Now imagine during your weight loss, is your TDEE being lower going to help or hinder you for sticking to an eating level? May depend on how little you really want to eat.

They lost in total CR - 8.3, CR-EX - 8.4, LCD - 11.2.

So while the LCD did lose the most (in 3 months too compared to 6), their TDEE had only recovered from 496 to 275 below what it could be, perhaps more recovery was coming. So no wonder the first few months of maintenance could be the hardest, you have the most suppressed TDEE then.

And notice that even the great results of the CR-EX group, still meant 8.4 lbs in 6 months of dieting, with a 25% deficit in essence, 12.5 created by diet, with additional 12.5 by extra exercise. But no loss of TDEE, in fact increase, and mere decent level of cardio.

Other point to keep in mind - no more than 2 x exercise a week was being done prior - so they had a lot of room for improvement. No weight loss prior, so full burning metabolism. And in overweight range, not obese where these effects might not be so bad.

Thought it was interesting info to know. So when you are talking about metabolism slowing down, it's more correctly your TDEE slowing down with all the components of it to some degree, beyond what was going to happen anyway. And recovery to expected levels could be well over 3 months when at maintenance. They reference another study where it took 6 years to.

HBO documentary Weight of the Nation discussing similar study, and the hormones causing the above effect. Further research shows the changes are not lifetime as implied.

http://www.youtube.com/watch?v=2i_cmltmQ6A 

[Dulce9]

Well guess what, Heybales.  The jury is in, and you're right and I'm wrong.  Though I'm glad to be wrong because I've lost more weight than Fitbit would have predicted.  I've been on this diet for 4 weeks with an average daily intake of 1830 and I've lost 6 pounds.  So that would put my TDEE at 2580, which was right about what I was guessing I was eating before, factoring in that I'm exercising a little more.  I know sometimes at the very start of diets you get a bonus couple pounds lost just because you are processing a smaller quantity of food in your body, so it's possible I only really lost 4 or 5 pounds.    Even 4 pounds would give me a TDEE of 2330.  So you're right--my actual TDEE is quite a bit higher than what Fitbit is giving me.  So far this diet is going well.  I can actually see the diminished fat on my body, and that makes me trust the lower fat percentage number on my smart scale.  

Now as for my friends in my little weight loss support group, one of them was instructed by her doctor to go on a 1000 calorie diet, and she did this for several months.  It worked while she was able to stick to it, but she has an extremely demanding job, and ultimately the diet was unsustainable.  Based on the study you were telling me about, it's possible that her TDEE might still be lower than predicted as a consequence.  

You give great advice on strategies to prevent...  what do we call it then...  I saw an article that called it metabolic adaptation.  How TDEE responds.  I remember reading about how the diet plus cardio group was able to stave off TDEE reduction, or whatever we call it.  The article I had read said that doing cardio each day would provide that benefit.  But now I'm wondering, does it have to be _additional_ cardio compared to what I was doing before?  I've been trying to exercise more, but Fitbit is only showing 50 to 75 calories more per day compared to what I normally do.  This is an average.  Of course I have great days.  Then there are crappy days.  I've had the habit of doing light cardio every day for decades.  

One lesson I'm getting from this is that it really is difficult to track small amounts of weight loss, and it's easy to assume that nothing is happening and give up.

So I thank you very much for your insight.  It's so important to have the facts in order to make smart decisions.  One thing I can see clearly now is that I'm in danger of winding up like the first group in the study, since my reduction is in fact around 25% (a lot more than I thought), and I'm only doing an insignificant amount of additional cardio.  I might need to make some adjustments.  

[Heybales]

Correct usually 1st maybe 2nd week of diet is some extra water weight lost too, usually tied to not storing as much glycogen in muscles with attached water, and less food passing through. I'd ignore the 1st week figure and just weight loss 2nd week on in your stats going forward.

So that's great it's more than thought, compared to other direction I mean. Still annoying, but at least a failsafe direction.

It's not additional cardio, it's some compared to little to none they had - the study they were doing the folks had barely anything. And it wasn't that intense either.

Now one of the reasons they always use cardio in studies is because they can get exact calorie burns for cardio, and that way confirm whatever deficit they want to be testing, is correct.

Like you and I could never trust a device or machine stated calorie burn to be exact, such that we could nail a 25% deficit eating goal from some daily burn for 3 months. Or 12.5% in calories from exercise and 12.5% less food eaten.

Because other studies over long term where they aren't testing this much deficit compared to this other deficit amount, but rather this workout compared to that workout, or this workout and resulting base metabolism - show strength training just or better than cardio at maintaining it.

But it is very difficult to nail lifting calorie burn to claim these 30 people had an avg 20% deficit from their daily burn.

But those studies do end up showing say no loss of LBM or less compared to cardio, or no loss of BMR, or similar.

And frankly in a diet, resistance training is what shows a retention of muscle mass (even if LBM drops) if the deficit is reasonable, and enough protein. Shoot, sometimes even when the deficit isn't reasonable for general masses - but those people are tested to see where that line is that is not extreme for them.

I do wonder about your workmates and 1000 cal diet from Dr. I've heard some state that also - but it was supposed to be for very limited time, then back up to some reasonable level. It takes awhile for the body to feel threatened at first, and genetics and other stress play in to how long that takes, generally Dr's specializing in that know to keep the extreme short, and then back up.

Sadly I've heard of your GP type family Dr recommending such things, and they never specialized in weight loss, merely going off their 6 month course on nutrition from schooling. Hence the reason they are supposed to recommend to a Dietician, same as recommend to Podiatrist or ENT for specific issues.