Hey bro, granted the 1,000 Cals for an hour of LISS is somewhat subjective (depending on gender, weight and type of activity) I based it on running 10k +. We know gender and weight already and there’s plenty of studies showing that would be a calorie burn of roughly 1,000 Cals.
This Harvard study gives info on other weights/activities.
https://www.health.harvard.edu/newsweek/Calories-burned-in-30-minutes-of-leisure-and-routine-activities.htm
Regarding changes in metabolism I’ll be honest, I’ve seen that as basically an accepted fact (although I accept I’m massively oversimplifying it using the expression ‘crashing metabolism). Lots of studies and links such as this:
Apfelbaum, M. et al. (1991). Energy-metabolism adaptation in obese adults on a very-low-calorie diet. The American Journal of Clinical Nutrition. Vol 53, 826-830.
But I didn’t think there was any doubt over hormonal adaptations to maintain homeostasis when in severe calories deficit. It’s also the logic behind accepted practices such as refeeds and reverse dieting.
I’m no expert and always learning so if there are more recent studies disputing this then I’d be interested.
Great response! At least you have some reason behind your thinking and I applaud that! I may not be right, it isn't cut and dry, but I have start by admitting this: if there are hypothetically 10,000 active users on AM right now, I would wager that 9,980-9,990 of them accept starvation mode and metabolic slowdown as being a big part of dieting and "fact". Then there is me. And the remaining 9-19 people may think...well, hit4me isn't totally off his rocker.
As far as the exercise calories...the chart you gave is pretty good but it gives a range of activities that would yield between 300-1200 or so calories per hour. Weight lifting itself for a 185 pound person is coming in at around 300 calories. I am not in great shape for running, I suck at it, and averaging 5 miles an hour for me is pretty challenging because I don't do it often. At that rate my treadmill has me at around 500-600 calories an hour and my fitbit says around 700-800. Both of those methods are often criticised for overestimating caloric expenditure, but 100-120 calories per mile run appears to be a reasonable estimate for someone between 160-200 pounds.
Now...your chart goes to much higher caloric ranges with harder intensities/tasks. If he is running at 6-8 miles an hour, which you and he may but I certainly can't nevermind calling it low intensity cardio, then 1,000 may be realistic...I hope to someday be there but I doubt most people are. I think, and I may be wrong, that running 7-8 miles in an hour is a real challenge for most people...not everyone, but I think you see what I am getting at. I could be wrong about the situation.
Getting back to starvation mode, I believe most people lose sight of the fact that calories are merely a measure of energy. Our bodies will adapt but it isn't magical like some people seem to believe. At the end of the day, it takes a certain amount of energy to do a certain amount of work. Our body cannot conserve energy beyond this point and, quite frankly, has no reason to waste energy just because we have more on hand so an elevated metabolism isn't logical either.
To illustrate further, if our body could adjust metabolism like a thermostat we wouldn't see the extremes we do in the world. Ethiopians would be carrying fat even though they are emaciated, and Americans would never get fat because their metabolism would speed up to accommodate all the food they eat.
But the fact is, Ethiopians may be emaciated but they still have muscles (albeit very small) even whilst having almost no bodyfat.
The idea is to store fat during times of surplus for expenditure during times of lack. Your very statement of the body holding onto fat because it is starving goes against survival. It makes sense to store fat for times of lack, but holding onto it during those times does not - doing so will decrease your chances of there even being a tomorrow.
Now, I agree, metabolism is dynamic and has factors. For instance, a big one you hear about is the fact that it takes energy to digest food, and different foods will take more energy than otgers, etc. But this is majoring in minors. Digesting food is very efficient and low energy. There are almost no foods that take more energy to digest than they provide. And most foods I doubt take 50 calories to digest 500 calories worth of output.
The reason this is a good example is because, if you fast you won't be digesting as much food, so yes your body will have a metabolism that is 50 or 100 calories slower. But, um, so what? You still have a net loss of 400+ calories from not eating the food. It isn't metabolic damage, it is your body not wasting energy.
And yes, you may become tired and lazy and this will lead to less activity and thus less caloric burn. And there may even be a balance here where you cam push harder in the gym, etc. With some extra calories and this will help you burn more. But it is really just an efficiency. It isn't like your body is magically reducing the calories it needs to accomplish a task, it is simply reducing those tasks.
And I agree that people who are in a big deficit often don't realize that they aren't moving as much during the day or aren't pushing as hard in the gym, etc. But again, it isn't a separate "mode".
The problem is that this thinking feels good. It lets people feel better about eating a little more - I am stoking the fire! - and it sells diet books. And people want to believe in it and they do, and it has become so prevalent that even scientists accept it as fact even though solid studies are hard to find.
The very study you supplied shows that previous studies don't show a reduction in RMR-LBM ratios. And the study itself seems to be showing that the LBM measurements may be the cause of this. But the very fact that are trying to prove a reduction in RMR among obese people who are fasting while other studies they reference show otherwise shows the attractiveness of the theory.
Still, the study you provided seems to be evidence of some slowdown. It is among the best evidence I have been able to find on pubmed...and as I've said I've read a lot of studies even that assume it is real within the study, but very few that rigorously test for its validity.
But...honestly, your response is among the best I have seen on AM for your side of it, and I would love to be taught more, I may not be right.
One thing I will also point out is that it dies make some sense that our body gets better and better are creating energy which makes us more efficient. A reversal of this efficiency never seems to be logical though. But you would expect exercise itself to have this effect. For instance, the example above, if you can run 8 miles and hour and I can run 5, you may be able to burn more calories overall per hour, but you will also be able to spend fewer calories to accomplish the same task I am accomplishing.
And another caveat - we obviously need nutrients to mobilize fat stores and undertake metabolic processes. Of we are simply lacking those chemicals because of malnutrition, we won't be able to mobilize the fat and those processes stop, but that is literal starvation.
