What I am saying is the energy balance equation does not account for plateaus that occur.
Well now that we're all friends again let the debate go on!...
I would have to disagree Keith.
The energy balance equation completely accounts for weight loss plateaus. Allow me to qualify this statement -
A weight loss plateau occurs when someone's energy balance equation comes into balance. In other words they are eating the same amount of calories as they are burning off and weight remains on a level. Whether they are eating 1000 calories and burning 1000 calories, or eating 5000 calories and burning 5000 calories makes no difference - weight remains on a level when calories in = calories out.
calories in < calories out (caloric deficit) weight goes down.
calories in = calories out (caloric balance) weight remains the same.
calories in > calories out (caloric surplus) weight goes up.
A weight loss plateau by definition is when a caloric deficit is followed by caloric balance (weight going down followed by weight remaining the same). When it comes to a weight loss plateau the energy balance equation is not in question. What is in questions is
"why has the person's energy balance come into equilibrium?".
There are two kinds of weight loss plateau - motivational and physiological.
A motivational plateau occurs above set point (ideal weight) and is the result of the person losing the motivation to either reduce calories in or increase calories out. For example, when someone is on a diet and exercise plan for a number of weeks (reducing calories in and increasing calories out) and then gives up the diet and exercise plan (increasing calories in and reducing calories out), bringing their energy balance equation back into equilibrium. Here the person needs to look at lifestyle, emotional and environmental factors that are affecting their energy balance, and try to find a sustainable exercise and nutrition plan to bring them down to set point.
A physiological plateau occurs at set point (ideal weight) and is the result of the person's physiology trying to bring their energy balance into equilibrium. This, dare I say it Keith, is where your biochemical processes come into play. For example, increased ghrelin levels and reduced leptin levels, making the person feel more hungry and therefore increase calories in, once again bringing the energy balance equation into equilibrium. And on the other side of the equation, another biochemical process involved in weight loss plateaus is muscle atrophy. The body burns off muscle tissue in order to reduce BMR and again bring the energy balance equation into equilibrium causing weight to plateau.
Why does the body do this? It's very simple. Our body has a weight that it naturally settles at - "set point" - and perceives going below this weight as a threat to survival. If you want to get below this weight it will resist by triggering physiological mechanisms that increase appetite (increasing calories in) or decrease metabolism (reducing calories out).
So all of the the biochemical processes you've been referring to are simply the body's way of adjusting the energy balance equation to maintain the body at set point weight. If you are going to mention leptin then you must understand it's place within the energy balance equation - it is one of the body's main tools for regulating energy intake (the left side of the energy balance equation).
There are people who follow the cals in vs. cals out routine for months (and even adjust BMR accordingly for weight loss) and then suddenly stop losing weight, stop losing measurements and don't see changes in the mirror.
The problem isn't the energy balance equation Keith. It is the somewhat suspect methods of calculating BMR. For example, many of the forumlas available on the web (Harris Benedict etc) are very misleading. There's only one way to accurately find out your BMR, and that's in a lab. Some people, particularly long term dieters, have a BMR well below what these forumlas suggest. I have taken part in research that proves how many long-term dieters, particularly those who have followed VLCDs, have a BMR well below what it should be. If they were to eat the calories suggested by these formulas, many of them would gain weight, let alone plateau.
As I mentioned before, the physiological plateau only occurs at set point weight. All people, without exception, will find that their set point weight occurs in the healthy range of bodyfat levels (although not neccesarily BMI),
so the truth is that there is no need to lose weight beyond this point. So now what needs to asked is
"if people are healthy at their set point weight, why are they trying to get below it?" The answer? Body image. This is where Keith's tape measures and mirrors come in.
So to conclude. There is a great deal of confusion between two very different weight loss approaches 1) the overweight person trying to get to set point, and 2) the healthy weight person trying to get below set point. Getting to set point requires a simple application of the energy balance equation. Getting below set point, which I'm guessing is what Keith is interested in, requires a more vigorous application of the energy balance equation. I can talk from personal experience on both approaches, having been 30% bodyfat in the past, well above my set point of 18%, and now sitting somewhat hungrily but sveltly at 10%. So it seems that I'm ruled by the mirror too Keith!
I assumed this was a forum for overweight people looking to get to set point, but if anyone here would like guidance on how to calculate where their set point lies, and advice on how to get below it, I'd be happy to help out.