Why 2 pounds/week max of weight loss?

You could, but then you would create too big a deficit and possibly stall your progress. That's why people recommend losing only 2 pounds or less per week. Also, if you're very overweight, it is normal to lose more than that early on in your weight loss journey. But if you're not too far off from your goal (30-40 pounds to lose), it's not medically healthy or safe to drop more than two pounds of weight each week. You should be eating back your exercise calories and maintaining a deficit that's right for weight loss, but not so big you stall.

Not to mention the more someone is in a deficit the less energy they have which equates to less intensity, which means less calories burned. Not to mention the ratio of fat to muscle loss doing just cardio in a big deficit will be slanted towards muscle loss, so you smaller, but fatter, yeah, that sounds wonderful.

You must also consider body composition during and at the end of the weight loss.

You only need to look around the forums here at the many threads made by people with tons of loose skin or zero muscle mass to realise it's not always a case of simply losing scale weight as fast as humanly possible

So it seems to me that if you have a LOT of free time to do cardio, you could shed weight quite a bit faster, without starving yourself.

You're right. It's how pro TdF riders can consume many thousands of calories per day yet still end up losing fat with no appreciable muscle loss. Many people do not have the time or the inclination to do it that way however.

You can also get really good body composition results using this method as well, with a certain number of caveats.

Firstly, you need to ensure you are eating a sufficient amount (so not under BMR as you suggest.) Usually your bodyweight in lbs times 15 is a good place to start.

You have to ensure sufficient macro / micro intake.

Sufficient resistance training must also take place.

Cardio has never been the problem, even a lot of it. It is excessive calorie deficits which cardio can add to if used recklessly.

It doesn't really make sense to me. You can lose a lot more if you incorporate cardio.

Like, suppose you do a 500 calorie deficit each day from eating 500 less calories than your base metabolic rate.

Then you do 1000 calories of cardio a day (roughly 1 hour say on an elliptical machine).

That is 1500 calories lost per day...3 pounds per week.

And obviously, some people can do more than one hour of cardio per day, and other are will to create larger food deficits than 500 calories/day.

So it seems to me that if you have a LOT of free time to do cardio, you could shed weight quite a bit faster, without starving yourself.

500 under BMR would be more than a 500 calorie deficit. BMR doesn't include regular daily activities, like walking around the house, etc. You mean 500 under TDEE like PP said. Also, this is MFP, not The Biggest Loser

I agree with the OP's maths but apparently it depends on your starting point. If you are obese*, then you can lose more than 2 lb per week. However, it is not a linear relationship (maths geek alert) between weight loss and calorie deficit, because there is a base amount of calories required for your body to behave, including burning fat etc

*Another rule of thumb is that if you are under 200lb, apparently your body won't support burning enough to lose more than 2lb per week, if you are over 200lb it will

So, is it a myth that any more than 2 lbs a week is muscle IF you do have a large amount to lose?

Pretty much. Altho if you simply cut your calories down and don't exercise, then your muscles will atrophy as you lose weight. A 400 pound man has a lot more muscle mass just to carry around his body weight, so he can handle some muscle loss while he gets back to a healthy weight. Getting in some exercise will help him save quite a bit of it tho.

So, is it a myth that any more than 2 lbs a week is muscle IF you do have a large amount to lose?

Pretty much. Altho if you simply cut your calories down and don't exercise, then your muscles will atrophy as you lose weight. A 400 pound man has a lot more muscle mass just to carry around his body weight, so he can handle some muscle loss while he gets back to a healthy weight. Getting in some exercise will help him save quite a bit of it tho.

Thanks!

So I was/am somewhat concerned by the point you guys raise about cardio killing muscle, not fat.

A few comments:

1. I try to counterbalance this by lifting throughout the week. Hopefully this sends the right signals to my body to keep the muscle and not lose the fat (hopefully my body is intelligent enough to realize that it should be burning fat for energy, not muscle, since that muscle will be needed tomorrow for the bench press and squat rack ).
2. I've ordered a scale with a body fat percentage monitor...I guess by tracking my body fat % over time as well as my weight, I can get a good sense of how much of my weight loss is fat versus muscle.

1. Your body needs fuel, there is no signal because your lifting that tells your body to use more fat.. Large deficits = Muscle loss.
2. Some of those BF% scales are not very accurate but you will have an idea.

Please don't post when you hit a plateau in your weight loss.

So I was/am somewhat concerned by the point you guys raise about cardio killing muscle, not fat.
1. I try to counterbalance this by lifting throughout the week. Hopefully this sends the right signals to my body to keep the muscle and not lose the fat

Cardio itself doesn't necessarily kill muscle instead of fat, it's not that simple and your calorie deficit will influence how much muscle you consume.

Lifting weights isn't going to give your body a signal to keep muscle and lose fat unless you feed your muscles/body appropriately and enough.

Also, this is MFP, not The Biggest Loser

LOVE IT!

You should eat under your TDE, but over your BMR (net). Which means, if you're working out, you should eat more to make up some of the deficit in order for your organs to still have the right fuel to function.

Also, whilst I'm sure some people could burn 1000 cals in an hour, I use a heart rate monitor and even when I'm working very hard, only get to about 400 per hour. So for a lot of people, burning that much a day just isn't possible.

By eating too little and pushing yourself too hard in the gym, you're just asking for your body to feel unwell.

It is possible. I am 5'9" at 255lbs and My heart rate stays around 165 BPM on average. If I am on an elliptical or walking up hill on a treadmill then I can reach around 947cal per hour. I am using a heart rate monitor as well. If you are smaller then you don't burn as much as someone has indicated. The bigger you are, the faster it looses until it starts to even itself out.

First, your deficit is deducted from your TDEE, not RMR/BMR.

Secondly, starving has to do with energy availability (net calories), not just the amount of food you eat.

My body requires 2900 calories to maintain itself while lifting five days a week. If I create a deficit from eating 1000 calories without any additional exercise, it is the same as if I were to eat 2900 calories and burn off an additional 1900 calories from additional activity. I would still be starving myself since they both equal to the same energy availability.

Finally, there is a limit to how much fat mass that can be oxidized in a 24-hour period which is based on total fat mass. The closer you get to that individual limit, the higher the ratio to meet energy demands comes from fat-free mass. Any deficit beyond that limit will not result in further fat loss within that same 24-hour period.

Then you do 1000 calories of cardio a day (roughly 1 hour say on an elliptical machine).

It would take upward of 2 hours to burn 1000 calories on an elliptical, I hate to tell you.

I weigh ~230 pounds, so the machine reports a pretty decent amount lost per minute. I guess for people who weigh less, they'll burn less.

Ah, I never thought of that. I'm only 152 or so, it takes me _forever_ to burn 500 cal.

It doesn't really make sense to me. You can lose a lot more if you incorporate cardio.

Like, suppose you do a 500 calorie deficit each day from eating 500 less calories than your base metabolic rate.

Then you do 1000 calories of cardio a day (roughly 1 hour say on an elliptical machine).

That is 1500 calories lost per day...3 pounds per week.

And obviously, some people can do more than one hour of cardio per day, and other are will to create larger food deficits than 500 calories/day.

So it seems to me that if you have a LOT of free time to do cardio, you could shed weight quite a bit faster, without starving yourself.

When I joined MFP I got the feeling it was designed to help with sustained wieght loss...like over several months. And once you reached your goal it would help you stay there.

Do it your way for three weeks and see how you feel and get back to us on wheather you think you can keep up that routine for several months.