Backpacking seems to contradict net above BMR

Ummmmm.....really dude....there's a huge difference between going on a backpacking trip or in my case a long cycling ride and being below your BMR on occasion and just netting below your BMR all of the time for weeks and months on end...I'm beginning to think you don't have a brain.

I tried to respond to this earlier, but after I typed out my long reply MFP went down and ate my post. :explode:

Here's the shorter version (the following contains generalizations and sweeping statements):

I have done a little backpacking, mostly day hiking. I went for 7 days to the Boundary Waters in northern Minnesota last year, and am going for 12 days to Philmont this summer. I have heard the same things about how much you can eat vs how much you burn, and how almost everyone loses weight on these treks.

There are important differences between eating chronically under your BMR, and netting under your BMR for a week or so while doing intense exercise. Backpackers are generally in fairly good shape, eat nutritious diets, and exercise a lot. Before they go backpacking they eat well, and when they're done they eat VERY well if my experience is any guide. Even though they are netting below their BMR, they are exercising a lot so that adaptive thermogenesis doesn't set in. The time frame of the trek is fairly short, so hormonal changes due to a relatively low intake don't set in.

By contrast, someone trying to lose weight with a VLCD over a long period of time is in a different situation. They are deliberately eating less than their body needs, and this is the goal of the thing. They are likely lacking in nutrients and probably don't have a lot of energy to exercise. This can go on for months, theoretically.

So both situations have "netting under BMR' in common, but they are quite different in terms of time frame, intent, and effort. I don't think backpacking is bad for you at all, but it certainly can stress the body. If someone were to eat and exercise like a backpacker for months, then I expect you would start to see the same deleterious effects expected from a VLCD.

Agree 100%. My point was not to try to argue that netting below BMR is great no matter what, my point was that context matters and that knee-jerking a "that's unhealthy" response to someone who netted below their BMR without paying attention to context can give the wrong advice.

The wrong advice is to say its fine obviously, since there are many many people who can be damaged by wrong advice saying VLCDs are "good" or "OK", and even if you are in error for a particular person or situation, the worst you are doing is "slowing" a person's weight loss. So, first, do no harm? Yes there can be a million reasons to fine tune advice one way or the other, and you can argue every one of them back and forth, but the fact remains you should advise against causing the common problems, and the serious problems, and warning against VLCDs does both. Its also extremely easy to self check and see "oh, not losing weight, better eat less". But its not so easy to go "you know I love this fast weight loss, maybe I'm doing something wrong", in fact there is a tendency to want faster loss, always.

As others have said too, there is an EXTREME difference between going on an intensive high exercise routine in a different situation, and exposing your body to all kinds of different stimuli for a week, and going on a VLCD for months at home. Obviously, stimulating the muscle and stress response helps keep the muscle. I have also done week long pack trips and eat less than I burn, and yes my legs were in great shape, but when I got back in the gym, my bench had suffered: you keep the muscle you use.