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How long does it take to slow your metabolism?


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I have noticed people talking a lot on here about how eating too few calories can slow your metabolism and keep you from losing or make you gain when you up your calories again. I was wondering how long this usually takes. Are we talking eating too few calories for a couple days, weeks, months?

I started trying to lose weight about 4 weeks ago and when I started I didn't really think about the metabolism thing. My calories have varied up and down but I usually average about 1000 calories under maintenance. But I have had a few days when it was fewer calories than that. Have I messed up my metabolism?

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i think it takes months or maybe a few weeks consistently under eating for the body to really receive the Signals.  perhaps you should eat maintenance Cal's for a while just to get your body to trust you if you think your metabolism might be affected in a negative way by the yo-yoing Cal's around for weight loss. maybe consistently eating the same amount everyday will allow your body to trust you and help you lose weight.

 

just an suggestion.

I assume it's different for different people. Back before I joined CC, if I went on a 1200 calorie diet (way too low for me), I would lose 15 lbs the first month and then nothing. Then as soon as I began eating, it came back. So it took about a month. If you're averagine an 1000 calorie deficit you might be fine, tracking your weight should tell you more.

There is a difference between 'starvation mode' and an adjusting metabolism. If you're eating too few calories, the body fears famine and will attempt to store everything you eat, resulting in no weight loss and quick regain. This is usually what people are referring to when discussing drastic undereating.

However, if you hit a plateau, that's just your body adjusting to your new calorie intake. In this case you stop losing weight, but if you eat maintenence, you don't regain it all back (maybe a pound or two). In fact, eating maintenence for a few weeks is often suggested to help break a plateau.

If you're averaging 1000 calories under maintenence, you should be ok. If you eat at least 1000 calories, sometimes more, you might want to consider aiming for a 700-800 calorie deficit, just to keep your metabolism jumping.

You'll know when you stop losing.  I had this happen over and over, just as minda_spk described.  I never knew what was going on, just that I couldn't lose weight after a certain point, and I couldn't keep it off.

It wasn't until I found CC and a kind friend explained it to me.  I was stalled on a long plateau and had decided to drop my calories even lower - to 900 a day because I was desparate.  Based on the advice I got right here, I consulted a nutritionist.  She put me on a 2000 calorie diet, warning me that I'd gain weight, but that it would level off.  It took about 3 months and a weight gain of 8 pounds to level.  Once I was stable, over the course of several weeks, she took away 100 calories a day until I started losing again.

Now I lose weight if I keep it below 1400 a day.  That's a lot more comfortable than starving, isn't it?

So my advise is to choose a meal plan based on the CC calorie reccomendations.  Stick to it even if you hit a plateau.  The only thing that works is long term consistancy and commitment.  If you do that you'll never have to diet again.

Original Post by valkyrie14:

I have noticed people talking a lot on here about how eating too few calories can slow your metabolism and keep you from losing or make you gain when you up your calories again. I was wondering how long this usually takes. Are we talking eating too few calories for a couple days, weeks, months?

I started trying to lose weight about 4 weeks ago and when I started I didn't really think about the metabolism thing. My calories have varied up and down but I usually average about 1000 calories under maintenance. But I have had a few days when it was fewer calories than that. Have I messed up my metabolism?

 

 As soon as  you lose weight, you will lower your metabolism.  That is not a bad thing as everyone seems to think, it's simply the way the human body works. 

Yeah, but we're not talking about the slight drop in metabolism due to losing a few pounds; that's normal.  The concern is when people consistently undereat and severely slow their metabolism so that their maintenance calories become far lower than they should be.

Original Post by susiecue:

Yeah, but we're not talking about the slight drop in metabolism due to losing a few pounds; that's normal.  The concern is when people consistently undereat and severely slow their metabolism so that their maintenance calories become far lower than they should be.

 Metabolism changes are normal, but also minimal for a person - they don't vary a huge % over a lifetime, but do lower with age, and occur in response to body weight and exercise.  Persistent "undereating" that causes a drop in body weight, will naturally reduce the metabolism.  Once you raise your body weight, metabolism raises accordingly.  

Original Post by fitmom4life:

Metabolism changes are normal, but also minimal for a person - they don't vary a huge % over a lifetime, but do lower with age, and occur in response to body weight and exercise.  Persistent "undereating" that causes a drop in body weight, will naturally reduce the metabolism.  Once you raise your body weight, metabolism raises accordingly.  

 If you weigh 300 lbs and eat 1000 calories a day, then what happens when you weigh 250 and you're maintaining at 1000 calories, what then? Cut more calories and starve to death? Someone should link to the article about the obese person that eats 700 calories a day. If you eat too few calories and your metabolism adjusts to low that would be 'bad.' Since it makes continued weight loss and weight maintenence impossible.

Original Post by sadinplaid:

Original Post by fitmom4life:

Metabolism changes are normal, but also minimal for a person - they don't vary a huge % over a lifetime, but do lower with age, and occur in response to body weight and exercise.  Persistent "undereating" that causes a drop in body weight, will naturally reduce the metabolism.  Once you raise your body weight, metabolism raises accordingly.  

 If you weigh 300 lbs and eat 1000 calories a day, then what happens when you weigh 250 and you're maintaining at 1000 calories, what then? Cut more calories and starve to death? Someone should link to the article about the obese person that eats 700 calories a day. If you eat too few calories and your metabolism adjusts to low that would be 'bad.' Since it makes continued weight loss and weight maintenence impossible.

What? Fitmom4life is totally right. Also, what 250 lb person would maintain at 1000 calories a day? RMR doesn't really change until you get down to 5% body fat, and then it tends to drop down to about 50% of the original RMR - so 50% of 1700 calories. But this only happens at a very low BF %, and understand that 5% body fat is the bare minimum needed to sustain life - the reason your body would do this is to keep you from dying, although if you kept cutting calories, you would still lose weight. A 250 lb person with 5% body fat would have to be very, very muscular. In that case, they would need way more than 1000 calories. And if they were not very muscular, they would still burn way more than 1000 calories. And they would be more likely to burn those calories as fat as opposed to lean mass, since a 250 lb person is likely obese (unless they're very tall or a body builder).

If you burn more calories than you consume, you will lose weight. It's simple physics. You can keep cutting calories, and guess what? You'll never STOP losing weight. Not until you die. Obviously this is not healthy, but my point is - minor drops in metabolic rate do not affect weight loss when drastically and unhealthily cutting calories.

When losing weight the healthy way, the reason weight loss slows down or plateaus is because your calorie intake/outtake has to be adjusted to your new fitness level and weight, since you're not drastically cutting calories. Most people only run a 300-400 calorie deficit, which means that in 10-20 lbs, they will hit a plateau where they're burning fewer calories because they have less weight. Thus, you eat a little less, and work out a little more or whatever. This usually breaks the plateau. Sometimes eating a bit more and working out a bit more works as well. But this does not mean that a 300 lb person will end up maintaining at 1000 calories a day @ 250, especially since 1000 calories @ 300 lbs is eating drastically fewer calories than would be necessary to maintain that weight. No one's metabolism slows down that much at such a high weight. I mean, maybe if they had hypothyroidism, or something.

Then explain the following:

Person A and Person B are the same gender, age, fitness level, etc.  They both start off weighing 175 and cut calories.  Person A cuts her intake to 1500 calories per day and loses a slow and steady 1-1.5 pounds every week.  Person B cuts her intake to 1000 calories per day and loses 10 pounds very quickly but then plateaus and cannot lose any more.  After six months, Person A weighs substantially less than Person B even though Person A is eating more.

The only explanation is that Person B is not burning as many calories every day as Person A.  The most likely explanation is that, because she's undereating, Person B has *no* energy.  So, she doesn't fidget at all.  She walks very little.  Even though they're both doing the same workout program, Person B isn't putting as much into the exercises.  She can't; she has no energy.  She doesn't realise any of this, of course.  Effectively, her metabolism has slowed down.  It's not just because she got smaller - because she's still bigger than Person A.  Nobody's suggesting that undereating makes your heart/brain/whatever burn less calories, per se.  But it *does* make your body as a whole burn less calories.  And it doesn't violate the laws of physics.  It's just sneaky.

The only thing that slows metabolism is muscle loss, which has more to do with a persons diet and exercise and to a lot lesser degree calories consumed.

Hunter et.al. : Resistance Training Conserves Fat-free Mass and Resting Energy Expenditure Following Weight Loss.

 Dieting groups who do no resistance training tend to lose muscle mass and experience significantly lowered REE both during weight loss phases and when calorie intake is normalized. This explains rebound weight gain - the effect is not the same one as the drastic slowdown associated with the extremes of low body fat(40%), rather it's on the order of magnitude of adaptive thermogenesis due to dietary restriciton, normally ~10%, 15-20% in cases of extreme restriction.

Redman LM et al, Metabolic and behavioral compensations in response to caloric restriction: implications for the maintenance of weight loss. Pennington biomedical research center.

In response to caloric restriction (CR/LCD combined), TDEE adjusted for body composition, was significantly lower by -431+/-51 and -240+/-83 kcal/d at M3 and M6, respectively, indicating a metabolic adaptation. Likewise, physical activity (TDEE adjusted for sleeping metabolic rate) was significantly reduced from baseline at both time points. For control and CR+EX, adjusted TDEE (body composition or sleeping metabolic rate) was not changed at either M3 or M6.

That is not a minor drop in resting metabolic rate. Coupled with the significantly reduced energy expenditure from behavioral adaptations to the restricted energy intake you are looking at an explanation as to why a persistent undereater/non-exerciser will maintain at a significantly lower energy intake than predicted by the metabolic calculators based on subjects at maintenance intake.

 In other words, yes, exactly the scenario you think is unlikely.

 Note the effect of resistance training on this - aerobic exercise basically does nothing to slow down the adaptations or prevent muscle loss, resistance training does even in the face of pretty extreme deficits. If you're in a population where resistance training is counter-indicated, you're much more limited in how agressive your calorie deficit can be.

Original Post by susiecue:

Then explain the following:

Person A and Person B are the same gender, age, fitness level, etc.  They both start off weighing 175 and cut calories.  Person A cuts her intake to 1500 calories per day and loses a slow and steady 1-1.5 pounds every week.  Person B cuts her intake to 1000 calories per day and loses 10 pounds very quickly but then plateaus and cannot lose any more.  After six months, Person A weighs substantially less than Person B even though Person A is eating more.

The only explanation is that Person B is not burning as many calories every day as Person A.  The most likely explanation is that, because she's undereating, Person B has *no* energy.  So, she doesn't fidget at all.  She walks very little.  Even though they're both doing the same workout program, Person B isn't putting as much into the exercises.  She can't; she has no energy.  She doesn't realise any of this, of course.  Effectively, her metabolism has slowed down.  It's not just because she got smaller - because she's still bigger than Person A.  Nobody's suggesting that undereating makes your heart/brain/whatever burn less calories, per se.  But it *does* make your body as a whole burn less calories.  And it doesn't violate the laws of physics.  It's just sneaky.

You're sort of missing the point here. I'm not saying that under eating DOESN'T make people less energetic and less likely to work out. It DOES do that. What I am saying is that, theoretically, if Person A and Person B had the exact same stats and were on the exact same work out schedule, Person B would continue to lose more weight than person A, until they reached a point of equilibrium. Which, at 1000 calories, would not happen for awhile. Weight loss would slow down, but it basically never stops.

At 1000 calories a day, 175 lb, 5'5'', and a RMR of 1800 calories, you would have to see a reduction in the metabolic rate of nearly 50% to be plateauing at 1000 calories! Even if the person did NOTHING, and lay in bed all day long - asleep, their BMR is still 1500. That would be a 33% reduction in their core metabolic rate, meaning they would have to lose a lot of mass - mostly lean mass - to be plateauing at 1000 calories. This does NOT happen unless you get down to a very low weight. Especially if Person B was also exercising. And more so because 175 at 5'5" is considered very overweight - almost obese, and it has been shown time and time again that people with more fat mass lose more fat mass than lean mass.

If Person B went down to 135 lbs, they would have a BMR of 1300ish and a sedentary RMR of 1600. Let's say that their metabolic rate slows down by 10% - their BMR would be 1170 (if they were catatonic) and their RMR would be 1440 (sedentary). Again, eating 1000 calories a day would still result in weight loss, though it would be slower. Even if their RMR dropped by -400kcal a day to 1200 a day, they'd continue to lose weight - but even more slowly. Of course, that's not counting exercise, or whatever. Eventually, the would plateau at 1000 calories, but if they reduced caloric intake to 500 calories, they would continue to lose weight once again. There have been studies done on this time and time again, which you can google if you really care.

My point is simply that weight loss will continue regardless of how little you eat, until you're dead. Of course, this isn't something anyone should try, because it doesn't usually end well. And in the long run, eating more is certainly better, because it allows you to have the energy to exercise, and thus allows you to run a larger deficit, resulting in more weight lost (to a point - 2 lbs a week is basically the limit to weight loss without losing a whole lot of lean mass unless you are obese or doing resistance training). Dieting always results in some metabolic slow down, but it's less than most people think - 7-10%, not 20% or 30% (unless you're not eating at all, and at a very low weight - but 1000 calories is not SEVERE restriction - though it is unhealthy). This slow down can be mitigated by eating sensibly and engaging in strength and resistance training, but it can never be completely avoided. Just keep that in mind when you plan your diet. A plateau is not the end of the world, and it can be avoided if you adjust your calorie intake accordingly.

Original Post by melkor:

Hunter et.al. : Resistance Training Conserves Fat-free Mass and Resting Energy Expenditure Following Weight Loss.

 Dieting groups who do no resistance training tend to lose muscle mass and experience significantly lowered REE both during weight loss phases and when calorie intake is normalized. This explains rebound weight gain - the effect is not the same one as the drastic slowdown associated with the extremes of low body fat(40%), rather it's on the order of magnitude of adaptive thermogenesis due to dietary restriciton, normally ~10%, 15-20% in cases of extreme restriction.

Redman LM et al, Metabolic and behavioral compensations in response to caloric restriction: implications for the maintenance of weight loss. Pennington biomedical research center.

In response to caloric restriction (CR/LCD combined), TDEE adjusted for body composition, was significantly lower by -431+/-51 and -240+/-83 kcal/d at M3 and M6, respectively, indicating a metabolic adaptation. Likewise, physical activity (TDEE adjusted for sleeping metabolic rate) was significantly reduced from baseline at both time points. For control and CR+EX, adjusted TDEE (body composition or sleeping metabolic rate) was not changed at either M3 or M6.

That is not a minor drop in resting metabolic rate. Coupled with the significantly reduced energy expenditure from behavioral adaptations to the restricted energy intake you are looking at an explanation as to why a persistent undereater/non-exerciser will maintain at a significantly lower energy intake than predicted by the metabolic calculators based on subjects at maintenance intake.

 In other words, yes, exactly the scenario you think is unlikely.

 Note the effect of resistance training on this - aerobic exercise basically does nothing to slow down the adaptations or prevent muscle loss, resistance training does even in the face of pretty extreme deficits. If you're in a population where resistance training is counter-indicated, you're much more limited in how agressive your calorie deficit can be.

Even if a 5'5'', 250 lb person with an TDEE of 2272 had a metabolic drop of 25% (higher than the one the above study found) eating 1000 calories a day (again more than what participants were fed on the LCD in the study quoted), and had a -560kcal drop in TDEE by M3, they would still continue to lose weight on 1000 kcal a day. I mean, up to a certain point, obviously. I'm not trying to start an argument, or anything. I'm just saying it is highly unlikely that a 250 lb person would stop losing weight at 1000 kcal a day. It's even more unlikely that this would happen if said person were doing some form of strength training, like you stated.

True, but at 1000kcal/d the diet for any male and most females would of neccessity be nutritionally deficient and lead to several different syndromes due to lack of adequate nutrient intake to support normal body function.

 It's why CC has the minimum limits it does on the intake recommendations - while it's possible to have an adequate diet under medical testing and supervision on that low a calorie intake, outside of a physician's care you're very unlikely to be able to achieve a nutritionally adequate diet on anything less than the limits in CC's recommendation engine.

 But you're changing your argument - you kept claiming that RMR doesn't drop at all until a dieter reaches body fat levels of a competition-ready body builder, which is clearly not the case.

 And an obese dieter who persistently undereats may lose 75% body fat on even a VLCD diet, but that still leaves 25% loss consisting of muscle mass - which is admittedly better than the 55/45 of the non-obese, but still extremely undersireable from a health standpoint.

 Also, the metabolic drop due to persistent undereating is not undone by cessation of calorie restriction - the metabolic adapations persist until weight is restored. Therefore, the low-calorie diets are counterproductive as they lead to a metabolism primed for weight regain.

Original Post by melkor:

True, but at 1000kcal/d the diet for any male and most females would of neccessity be nutritionally deficient and lead to several different syndromes due to lack of adequate nutrient intake to support normal body function.

 It's why CC has the minimum limits it does on the intake recommendations - while it's possible to have an adequate diet under medical testing and supervision on that low a calorie intake, outside of a physician's care you're very unlikely to be able to achieve a nutritionally adequate diet on anything less than the limits in CC's recommendation engine.

 But you're changing your argument - you kept claiming that RMR doesn't drop at all until a dieter reaches body fat levels of a competition-ready body builder, which is clearly not the case.

 And an obese dieter who persistently undereats may lose 75% body fat on even a VLCD diet, but that still leaves 25% loss consisting of muscle mass - which is admittedly better than the 55/45 of the non-obese, but still extremely undersireable from a health standpoint.

"RMR doesn't really change until you get down to 5% body fat, and then it tends to drop down to about 50% of the original RMR - so 50% of 1700 calories. But this only happens at a very low BF %, and understand that 5% body fat is the bare minimum needed to sustain life - the reason your body would do this is to keep you from dying, although if you kept cutting calories, you would still lose weight."

Perhaps I misstated what I meant in the above sentence. What I was attempting to say was that RMR does not drop down to a very low number until one has lost a high percentage of body fat via famine-like starvation. I should have articulated that better.

A 250 lb person with 5% body fat would have to be very, very muscular. In that case, they would need way more than 1000 calories. And if they were not very muscular, they would still burn way more than 1000 calories. And they would be more likely to burn those calories as fat as opposed to lean mass, since a 250 lb person is likely obese (unless they're very tall or a body builder).

No one's metabolism slows down that much at such a high weight."

I stand by this statement.

Also, I was in no way advocating a very low calorie diet - I was just trying to make a point.

Original Post by asphyxiac:

You're sort of missing the point here. I'm not saying that under eating DOESN'T make people less energetic and less likely to work out. It DOES do that. What I am saying is that, theoretically, if Person A and Person B had the exact same stats and were on the exact same work out schedule, Person B would continue to lose more weight than person A, until they reached a point of equilibrium. Which, at 1000 calories, would not happen for awhile. Weight loss would slow down, but it basically never stops.

No, I'm not missing the point.  I think you might be.  Person A and Person B might be on the same workout schedule on paper, but they're not burning the same calories in practice.  How many calories you burn in a workout (or even just during the day doing regular stuff) is strongly correlated to how much effort you put into those activities.  When undereating, a person simply doesn't have the energy to put a full effort in, so they burn less calories because they're doing less (even though they may think they're doing the same; not all half hour runs are equal).  And they're not doing a ton of little things like chasing their kids around as much as they used to or folding the laundry standing up or whatever.  So, we say that undereating slows down your metabolism because that's the end result.  For a site at which most people are concerned about the most effective way to lose weight and keep it off, that's sufficient.  Eating a reasonable amount *is* a more effective weightloss strategy than undereating.  Just ask any of the people around here losing weight on 2000-2500 calories/day - or the folks stuck on plateaus eating 1200 calories/day.

Yes, there's a point at which you lower the calories so much that the body can't compensate by slowing itself down.  That's true starvation (rather than 'starvation mode' or 'conservation mode' or whatever you want to call it). 

Original Post by susiecue:

Yes, there's a point at which you lower the calories so much that the body can't compensate by slowing itself down.  That's true starvation (rather than 'starvation mode' or 'conservation mode' or whatever you want to call it). 

Then we agree!

A further point on the "why low calorie diets are universally bad" list is that they generally don't work and prime the dieter for weight regain.

 The REE slowdown due to persistent undereating persists until weight is restored and for some time after. It's not clear from the current studies whether resistance training can really prevent this in a low-calorie situation even if it does prevent the metabolic slowdown in the short-term studies, you bump up against the limits of what your body can mobilize from fat stores as well at some point.

 What is clear is that low-calorie dieting screws up your metabolism for the long term and is the most consistent predictor of weight gain in individuals who don't develop full-blown anorexia and die from it instead.

Original Post by asphyxiac:

Even if a 5'5'', 250 lb person with an TDEE of 2272 had a metabolic drop of 25% (higher than the one the above study found) eating 1000 calories a day (again more than what participants were fed on the LCD in the study quoted), and had a -560kcal drop in TDEE by M3, they would still continue to lose weight on 1000 kcal a day. I mean, up to a certain point, obviously. I'm not trying to start an argument, or anything. I'm just saying it is highly unlikely that a 250 lb person would stop losing weight at 1000 kcal a day. It's even more unlikely that this would happen if said person were doing some form of strength training, like you stated.

 I'm going to go ahead and state that based on research, the medical community still does not know everything there is to no about metabolism and physiological compensatory actions. Honestly, I have no intention of spending hours looking up the pertinent research here explaining the why's and what for's (that's what Melkor is for, he's always up on the research). Me, I'm more of statistician, and I can tell you what the DATA says.

There are a lot of obese people that eat drastically low calories. This isn't my friend of friend's mom, these are people being closely monitored and studied, and it's not some rare exception, it's actually pretty common. People who have yo-yo dieted are more resistant to weight loss, how does calories in vs calories out explain that? Sounds like a metabolic change. People who are obese and take up severe calorie restriction will still plateau. So there are 200-300 lb people (high body fat %) that consistently eat 700-1200 cals a day and never lose a lb. That's a pretty drastic metabolic change.

This isn't a minor relationship, the body adjusting to low calorie intake. It's a very clear, unmistakeable relationship that a bit of research will turn up in no time.

I agree with what alot of people of saying.  A couple of years ago after I had my son, I went into crazy diet mode.  I was only taking in 400 cal per day, and I lost all of my baby weight and that was probably the smallest I had been since high school.  It took about 3 years for that weight to come back and I am paying the price for it.  I can't drop a pound to save my life let alone 30lbs.  My metabolism is shot.  If I look at someone else's burger I seem to gain the weight Smile  Well this time I am going to try and do it the right way and really learn how to eat this time.  I do agree with the key being getting your body to trust you.  As long as you are not depriving your body or at least eating more frequently when you eating fewer calories then you should be fine.  Don't quote me on this but as long as we are taking in food/beverage every 3 -4 hours your bodies metabolism will not slow down...it actually increases it.

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