Impossible to lose more than 2lb bodyfat per week?

I don't understand how its impossible.  I was Approx 300 lb the first time I dieted, and within maybe 7-8 months I was down to 175 and had plenty of muscle.  I was very strict with my diet and exercised.  So whats up with that?

Also how can a number even be placed on something like that, shouldn't it vary person to person based upon a good deal of variables. 

I let myself go pretty good and I'm back up to my 270s but I'm strict again and its falling just as fast.

I have a friend who had lost 40lbs in 2 months and was noticably thinner as far as fat goes.  How is that possible if losing more than 2lb bodyfat per week is impossible? 

In 2 months, that should be a max of around 16-19lb bodyfat if he lost bodyfat only.

So that means the rest would have to be water weight and muscle loss?  I really dont think thats right...  Plus those numbers 16-18 are dependant on if he did lose the max 2lb bodyfat / wk.

Anyone wanna help me understand?

There's a biochemical limit to how much energy you can get from fat in a day due to the limitations of the reaction speed of the lipase enzymes that work to mobilize fat stores for energy.

A limit on the maximum energy transfer rate from the human fat store in hypophagia is deduced from experimental data of underfed subjects maintaining moderate activity levels and is found to have a value of (290±25) kJ/kg d. A dietary restriction which exceeds the limited capability of the fat store to compensate for the energy deficiency results in an immediate decrease in the fat free mass (FFM).

S.S. Alpert Journal of Theoretical Biology Volume 233, Issue 1, 7 March 2005, Pages 1-13

Works out to about 31cal/lbs of fat mass/day on average. Also note that the 31kcal/lbs is a biochemical max under ideal circumstances; most people will in fact start to experience loss of lean mass at around 20-25kcal/d, especially if they aren't doing the right kind of exercises that will help upregulate the efficiency of your body's energy systems. So don't push this to the bleeding edge of what's possible due to the inherent uncertainties of the measurements we have outside the lab, but it's good to know that there's room for individual adjustments, neh?

 As a general rule this works out to about 1% of your total body mass a week; or for most people who are under 200lbs about 2lbs per week. As long as you had larger fat reserves than the baseline norm the generic diet is constructed for you could in fact lose faster safely as long as some rules about exercise are observed; i.e. that cardio won't do jack to properly preserve muscle in a deficit, only strength training will.

So yes, if you were losing faster than that limit, you were in fact burning muscle for energy, it's the only other source of energy your body has and if you're trying to beat biochemistry by crossing your body's limit for burning fat, that energy you're expending has to come from somewhere. Or perhaps organ mass, bone mass, that sort of thing - but you can't beat biochemistry. There's a limit, and it's not physically possible to cross it without ill effects. Unless you're resorting to the bodybuilder solution; using more drugs than any three hospitals to make your metabolism completely inhuman.

It's possible to do a lot of things but losing more than 2lbs a week doesn't work in the long run.

Eating a deficit of more than 1000 calories until you can't stand it any-more isn't teaching anyone how to eat for life and so people then put the weight back on over the next few months.

Eating in a way you intend to keep up forever (including a realistic amount of indulgence) and exercising an amount you intend on keeping up forever might not lose you more than 2lbs a week (in fact some weeks it might not lose you anything) but once you do get to the correct weight you'll stay there for life.

A 1000 calorie deficit is in order in my opinion if the original caloric intake is well above what a healthy intake is.  Ex:  Someone who constantly eats out and eats horrible foods, like I was,  I had to have been bringing in at least 3000 - 4000 a day.  I've cut down to 1500.  I did before, and lost 125lb and had good body muscle, in 7 months

Melkor gave you the science, so I'll just add that the common statement that you shouldn't lose more than 1-2lbs a week is based on average people weighing less than 200lbs.  If you weight 300+, you have more fat and a higher BMR, and can therefore more easily burn fat before turning solely on lean muscle.

To put it another way, it's a lot easier to have a calorie deficit when your maintenance calories are 3000+ at 300lbs versus 2000 at 150lbs.

Original Post by vwiggins:

Eating a deficit of more than 1000 calories until you can't stand it any-more isn't teaching anyone how to eat for life and so people then put the weight back on over the next few months.

Eating in a way you intend to keep up forever (including a realistic amount of indulgence) and exercising an amount you intend on keeping up forever might not lose you more than 2lbs a week (in fact some weeks it might not lose you anything) but once you do get to the correct weight you'll stay there for life.

Just want to echo this.  OP, 1500 calories is the absolute minimum for a guy - and that would be a short, normal-weight or slightly overweight guy.  At your current weight, you should not be going this low.  You're messing up your metabolism and setting yourself up for failure.  How low are you going to have to go once you get back down into the 100s? 

I know you said you did it before, but you were unable to maintain at that weight so something wasn't working (your other post said baby / life, but there's always going to be something).  Now I may be one to talk, since I've done the same thing on a less extreme scale (~50 lbs), but I've seen the error of my ways and changed them.

Also, your calorie deficit isn't based on what you used to eat vs. what you eat now, it's what you could eat to maintain vs what you eat now (there may be a difference), just FYI :)

All that said, YOU can lose more than 2 lbs of fat a week, at least at first, since you're well over 200.  And you probably have some excess muscle mass that it won't particularly hurt to lose, although I do think you'd be better off keeping as much of it as possible.