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Calorie Burn Decreasing

I know that as you become more fit and your body adjusts to the workouts, as well as when you lose weight, that you will no longer burn as many calories as you may have initially. At what point did you start seeing that decrease? I've been working out consistently maybe 2 months now, and for example initially during a boxing class according to my Fitbit I would burn maybe 450 calories an hour, versus now maybe 390. The class definitely still feels challenging to me, and there are still moments when I physically can't do certain exercises so I don't think I'm at a point where I need to add weights or something to make it more challenging..lol it still is with ALL my body weight! I'm nowhere close to goal weight so I didn't expect to encounter this issue this early on.

But I'm already working out most days 2 hrs a day so working out longer to burn more calories isn't really realistic in terms of having the time. Most days I'm only eating about 1500 calories so I don't want to decrease this early on in the game.

I'm consistently not hitting my calorie burn goal for the day...any tips, suggestions?
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As you weigh less you will burn less calories with the same workout. The same workout that once had me burning almost 300 calories now has me buring about 200.

 

Look at your nutrition. What is the mix of the food you consume? (% fat/carbs/protein) Perhaps consult a trainer or nutritionist to come up with a nutrition plan to match your goals and activities.

 

When I was in a serious plateau but felt like I was killing myself my trainer told me I needed to eat more, but different things. Once I changed my diet the loss picked back up.

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Right...I agree.

 

Just curious though, how soon did you see a drop in your workout calories from the 300 to 200?

 

I knew it would happen, but I just didn't expect it to happen so quickly I guess!

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If these workout calories are based on HR - then what you are observing is false changes if weight hasn't changed a lot.

 

The same weight being moved at the same intensity (pace/speed, whatever) will burn the same number of calories. Unless it's an activity you have gotten massively more efficient at. Like if your Zumba movements the first few times were just all over the place, but then you got smooth with them. But that's really minor, and doesn't normally apply to running/walking which people have been generally doing since little kids.

 

The HR merely shows that if high is was mainly carb burn as unfit level, and lower as higher % fat burn as more fit level - if it is changing.

 

Because you at same weight same speed running, with HR at say 160, and then 1 month later at 140 but no change to weight - would have a changed VO2max.

 

And sadly some devices would assume since weight is the same, VO2max is the same - but that stat actually improved.

 

You can now take in more oxygen with each breath and get it around the body with less beats of the heart.

So you are burning the same amount of calories, but more fit means higher % of fat burned than before.

 

Now I've had people notice that their calorie burn becomes more accurate after first week or two of use.

Because Fitbit doesn't know your VO2max - they are trying to estimate it.

And a great public research study with decent estimate is using your BMI, resting HR, and calculated HRmax, and frequency of exercise.

2 of those stats improve in accuracy the more you wear it.

So if a week or two is time for use - it's likely that change to accuracy.

 

After a month of usage, and your resting HR lowers, even if rest of the stats stay the same - your VO2max goes up in the estimate.

Meaning it'll probably show you burning the same calories (or close) despite the HR being lower.

 

But hopefully at that point you are also going faster since more fit.

 

 

Also - only eating in total 1500 calories while working out for almost 2 hrs daily? Or almost Daily?

 

That is one extreme deficit it sounds like - you have no idea how good your workouts could be with a more reasonable deficit.

That's why a good HR-based calorie burn MUST incorporate VO2max - which is that level of fitness you are currently at.

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I have seen this in my own experience.  When I started cycling, I was burning roughly 8-9 calories per minute.  Now, with the same intensity, I burn 5 to 6, after a few months of cycling.  The reason is simple, the body is more efficient.

 

As you become more fit, the resting and exercise heart rate will drop, burning less calories.  When I was in 70+ BPM resting heart rate, I would burn more daily calories than my current 55 BPM resting heart rate.

 

You will get to a point when exercise will result in diminishing returns for weight loss (not health) and you will need to focus more on your diet, or constantly try to increase your intensity.  With bike riding, you can only ride so hard, so there are limits.

 

I can rarely get into the "peak" heart rate, whereas before I would get to it easily.  You will probably notice that "active minutes" start dropping off too.

 

 

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@MattJ71 wrote:

I have seen this in my own experience.  When I started cycling, I was burning roughly 8-9 calories per minute.  Now, with the same intensity, I burn 5 to 6, after a few months of cycling.  The reason is simple, the body is more efficient.

 

As you become more fit, the resting and exercise heart rate will drop, burning less calories.  When I was in 70+ BPM resting heart rate, I would burn more daily calories than my current 55 BPM resting heart rate.

 

You will get to a point when exercise will result in diminishing returns for weight loss (not health) and you will need to focus more on your diet, or constantly try to increase your intensity.  With bike riding, you can only ride so hard, so there are limits.

 

I can rarely get into the "peak" heart rate, whereas before I would get to it easily.  You will probably notice that "active minutes" start dropping off too.

 

 


You have hit upon one of the reasons why HR is not a "measurement" for calorie burn.

Rather it can be used in a formula to calculate calorie burn. Big difference.

But there are many caveats to it being close or far from accurate.

 

If you squat 200 lbs early in strength training and it's really hard for you, and then a year later you squat 200 lbs during the warmup of getting up to 400, and you weigh the same - is the energy required to lift that 200 lbs different just because it feels easier?

 

No - it's the same - you are just recruiting more muscle fibers and CNS is firing better.

The energy needed to lift that 200 lbs is exactly the same. Just feels easier. Same calories from energy expended.

 

You aren't burning less if the intensity in your cardio is the same - except for the super minor difference between heart rates in calorie burn.

If weight is the same.

 

You should look up the posted RMR tests people get at different stages of fitness, but you have to compare when weight is the same. Their base daily burn is the same even if restingHR has gone down, except again for the very minor difference in HR calorie burn. But the body as whole is still expending energy on the same functions as when unfit.

 

The workout feeling easier is meaningless for calorie burn, same as thinking because you sweat up a storm you must have burned a lot, your heart rate being lower merely means you are able to use more fat as energy source compared to carbs you used when out of shape and it ran higher.

And the HR can increase for a workout totally unrelated to the intensity or work load being higher - dehydrated, body hot, stressed (lack of sleep or recovery), meds or stimulates. HR can increase for those things and it doesn't mean you burned more calories than a normal lower HR doing same workout.

 

If you have become more fit - it means the device was overestimating calorie burn then, and may be underestimating now.

Parts of the calculation are restingHR, HRmax (which is calculated and many find not accurate at all), age, gender, BMI (healthy range is figured to be better VO2max), and Fitbit may be using workout frequency & duration weekly like some of the others do now. It's from a research study and public domain so probably are.

And we probably know many healthy BMI people in terrible fitness shape so VO2max (used in calorie calc) would be thrown off, as well as many in higher BMI in great fitness shape, also throw off calcs.

 

Now - inability to reach HR zones (which may not be right anyway since based on calculated HRmax 220-age) may mean they aren't right - or you aren't pushing hard enough.

 

Because indeed as you get fit you do have to push harder to still make it a workout for the cardio system. If you've gotten lighter then even harder.

(like lifting 200 lb squat - if you lost 50 lbs body weight and still did 200 - are you even maintaining strength?)

 

You need to get a power meter for your bike and discover the truth of that calorie burn matter - HR and those estimates don't work on outdoor riding and it's interval nature if hills are involved.

But even if flat you can see the fact that if you are pushing harder to get the HR higher like it used to be - you are expending more watts, or energy, or calories.

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I know this is a very old post, but I'm hoping you'll reply anyway. What things did your nutritionist tell you to eat? I've been exercising for about three months, lost loads of weight and now I'm at the weight I want to be, I'm terrified of putting it all back on again. I still have a massive deficit in ingoing/outgoing calories (1000ish) but I'm afraid if I lose that, I'll balloon. I'm also still exercising for several hours a day but when I go back to work I'm not going to be able to maintain that. How do I proceed from here?

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@Freya_C wrote:

I know this is a very old post, but I'm hoping you'll reply anyway. What things did your nutritionist tell you to eat? I've been exercising for about three months, lost loads of weight and now I'm at the weight I want to be, I'm terrified of putting it all back on again. I still have a massive deficit in ingoing/outgoing calories (1000ish) but I'm afraid if I lose that, I'll balloon. I'm also still exercising for several hours a day but when I go back to work I'm not going to be able to maintain that. How do I proceed from here?


Massive deficit is great way to stress the body out.

So you are losing currently 2 lbs weekly still if that deficit is true.

 

Count on probably 25% of that to be muscle mass - that should freak you out because that is exactly what makes it so easy to cause fat gain later.

Most people cause their own dieting rebounds by the extreme nature of what they did - sounds like you are doing that too.

 

You should put on the water weight you initially lost in first couple weeks of starting the diet. Good body-desired water weight for storing more glycogen in the liver and muscles.

You should not have a weight goal, but a weight range goal - otherwise you'll drive yourself batty. Measure your waist too.

Hopefully you've observed the easy nature of water weight change, up and down. If it was fast, it was water weight. Fat is not fast lost or gained.

 

Fitbit was attempting to teach a life lesson about weight management many do not know.

You do more you eat more.

You do less you eat less.

In a diet a tad less in either case.

 

Did your eating goal change almost daily, and did you indeed eat different amount daily? (roughly, weekly balance is good enough)

Good - you learned the lesson.

So what do you need to do when you go back to work and not workout for hours a day?

 

As to how to get out of the extreme diet you are in without causing worse effects on your body?

Right now - right now - start eating 200 extra calories daily for a week.

Week after another 200 daily.

Should have 5 weeks of that if you truly have a 1000 cal deficit losing 2 lbs weekly.

If you stop exercising as much and return to work, then obviously don't keep increasing and eat more than you burn - right?

At which point you may be eating near maintenance.

Any fast weight changes are water.

Realize you'd have to eat 3500 calories ABOVE maintenance to gain 1 lb of fat. Reread that until it sinks in.

If you gained 1 lb from 1 day to the next - did you eat some 5500-6000 calories between the weigh-ins? (estimate, and most of that weight is food in gut at that point - it'll be leaving soon)

 

Hopefully you've been eating in a way you can sustain to keep the weight off - like foods and meals you will move forward with. If your diet has been totally stuff you can't keep eating, then you've got some retraining to do.

 

You can do this, even if the approach to get here has not been the best method for continued success, you can make the changes now.

What you eat is what you can adhere to. There is no magic bullet to solve this. What's great for one could be useless to another, or a really bad idea.

Some people can have a bag of chips they love, and enjoy a serving or two knowing they get more tomorrow. Some can't put the bag down and finish it off way overeating. That is personal to you, and you should have some idea now what may work or what really won't at all.

Write it down. Write down all the things that are good for instance review.

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Thank you very much for replying! I've taken your advice and have now reduced the amount of exercise I do a bit and am trying to actively eat a bit more to raise daily deficit to 750, will gradually reduce calories burned through sport and increase the amount I eat to reach a happy medium in the hope of staying where I am. I do indeed have a desired range (50-52 kg). I'm sorry but I don't quite know what you mean by water weight. Could you explain? I'm also not sure what would entail fast weight loss, I think mine has been pretty ok?

 

I've had a look through my stats in more detail. So in the last 5 months I've lost 14kg, from 64 to 50kg now (I think that's 30lbs). I haven't gained weight through that process, and have lost a kilo or two every two/three weeks. This has mainly been by doing LOTS of exercise, my diet hasn't changed much. I never used to eat that much anyway, though now I've cut down on booze and deepfried or processed food, but that's no hardship as I never eat loads of that stuff.

 

I think I eat healthily, and I'm happy with what I eat. Lots of veg, only eat meat a few days a week, but I do eat yogurt and eggs every day. Lots of hummus, pulses, avocado and that sort of thing, wholegrain or brown bread, some fruit.

 

The exercise has been varied, I do some weight training every other day, walk 5+ miles a day, some cardio every day, though varied in intensity. I try to have one day where I only have a walk as a rest day.

 

I'm happy with how the weight has gone, my waist is 78-ish cm now, was much bigger before though I don't remember how much. I have defined muscles in arms and legs, and even some in tummy (under stubborn layer of flabby fat/skin). 

 

Over the last few weeks the weight has stayed the same despite still having had a 1000ish calorie deficit. That was/is the worry. It's weird! And because I'm not losing more now, I worry that if I am less active or eat more I will start gaining again. As I say, I'm going to try to slowly close the gap between calories in and out and see how I go. Do you think that's the right way to go?

 

Thank you again for responding.

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Sounds like you are at goal weight then?

You said desired range of 50-52 kg, and you've lost weight over 5 months to 50 kg.

If that is true - you should not have a deficit then for more fat loss if that is healthy weight range.

 

Fast or slow depends on how much you have to lose to what the body would consider healthy. Bad things happen when body is stressed.

When you have plenty of fat to lose, like over 50 lbs - then 2 lbs weekly for average person isn't seen as extreme and body doesn't react negatively.

When less to lose, like under 15 - then most find 1/2 lb weekly isn't stressful and body works with what you are doing.

Sadly many attempt to keep the rate high too long, body adapts and forces it slower anyway, and remains stressed.

So much better to reduce the rate purposely than have it forced on you.

 

To really have a best estimate of your daily burn, some tweaks are probably in order.

Strength training should be logged manually as Weights if doing sets and 5-15 reps and 2-4 min rests between sets. Circuit training if 15 up reps and rests up to 1 min.

HR-based calorie burns on that workout is going to be inflated calorie burn. Reported more than actually happened.

 

Your walking would be best confirmed for distance - walking known km or so and confirming Fitbit got it right, should be at average daily pace between grocery store shuffle and exercise level pace. Stride length should be set for that middle value - device can then adjust up or down as needed for whatever you are actually doing.

 

When you have a lot to lose inaccuracies and bad estimates aren't so bad. At maintenance or little left to lose - no good.

 

Is your food logging by weight?

Great nutritious variety, but for accuracy calories is per gram, not per slices, or egg, or cup or spoon volume measurements.

 

So it would be hard to really know if you are gaining water weight from stressed body attempting a big deficit, unless you have inches on stomach going down, which sounds like last place to lose for you.

If no inches - you don't really have a deficit in place and your estimated calorie burn and calories eaten is off.

If inches have been coming off in last few weeks (and it may not be just belly) with weight the same - water being added from stress.

 

Tighten up the logging no matter what, making those improvements so you really have best estimate of what you burn and eat.

Depending on inches lost and if water is being added - that determines next steps.

 

Because water is without calories obviously, so if water weight added you wouldn't reduce calories.

Like if someone drank 16 oz of water before stepping on the scale in the morning, saw an increase of 1 lb weight, and decided they better eat less food that day - we'd call that foolish.

Your rate overall doesn't seem bad at all, and likely was more at first and less later, hopefully because you purposely did it.

If it just happened - your body adapted. That's not good.

 

Water weight - you know that first week starting a diet, vast majority report big loss of weight?

That is from taking in less carbs usually, body can't fill the muscle stores like it once did, carbs store with water. Water weight.

Once you finally eat more, and body can finally store more carbs like it wants to in order to support your activities - water weight back.

Good, healthy, body desired, improve your workouts water weight.

Water weight also happens when you start exercising, more blood desired for cooling effects, for reaching more vessels grown into muscles needing more oxygen, increased blood volume.

When you are sore, or may not feel sore but body is inflammed from good workout, water retained for healing purposes.

Time of the month - probably need no help knowing about that one.

Stress upon body - lack of recovery from workouts before hitting muscles again, lack of sleep, life, bigger diet than body is happy with - leads to increased cortisol hormone - that can cause water to be retained in the cells and between the cells of the muscles and other areas through the whole body. Speculated to include in fat cells (because of the swoosh many experience when they eat more and they pee a lot one day and drop many pounds and lost inches and fat feels funny compared to other times).

 

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I would suggest cross training. Jogging, elliptical or rowing.  Something that is high intensity.  Or try to do a 3 mile walk, on the days you are not boxing.  Also adding more veggies to your diet.  It will make you feel more fuller with a lower calorie count.  I see you are doing calorie counting.  Are you counting the fluids that you are drinking? Cut back on sugary juices, teas, and coffees.  I have a glass of OJ or grapefruit juice in the morning.  The rest of day would be water or coffee with no sugar or cream.  Getting in shape and being healthy are hard.  You have to put the work in.  Please don't get discourage that you are not burning enough calories that day.  You are burning calories and you are doing it.  Develop a routine that you are comfortable with and stick with it.  Eventually, you will be happy with the results.

 

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Everything you’ve said rings true for me. I’m working just as hard, if not harder but the active calories are dropping, making it harder to reach my calorie burn goal, and harder to get the deficit to lose weight. Thinking of slowing down with the exercise or having rest days so that cycling 30km each day actually delivers some reward. 

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