Archibald posted a link to Issues and Misconceptions About Obesity, the infamous Flatt paper.
Since this part was "hot" right now, I decided to blog on this, also because the issue has come up in other recent comments.
9. Conditions for body weight stability: “settling point” vs. “set point”
Although less obvious than the fact that energy intake must be equal to energy expenditure, weight stability also requires that the substrate mixture oxidized be equivalent, on average, to the composition of the nutrient mix consumed. When “substrate balance” is not achieved, changes in body composition occur, which in time are bound to elicit adjustments in food intake. Weight maintenance thus tends to become established for a particular body composition in a given individual living under a particular set of circumstances. This corresponds to a “settling point”. Such a view accommodates the fact that circumstances cause weight stability to occur for various degrees of adiposity. Thus it seems to fit reality much better than the concept of a “set point” or “ponderostat” often invoked to explain weight stability. In fact, such a concept would seem to be utterly inconsistent with the rise in the preponderance of obesity, since set-points would have to be seen as preventing the impact of changing circumstances. It has sometimes been considered that “set-points” are reset for different conditions, but in effect this argument reduces the set-point phenomenon to a settling point.
In Part II I'll address the concept of substrate balance eluded to in this excerpt and expanded upon in the remaining paragraphs of this section. For now, however I have some thoughts and questions on the concepts of set point vs. settling point in general. The set point concept basically states that our bodies have a fixed weight that is set/programmed genetically. This is supported by experiments of overfeeding and underfeeding normal animals and their weight returning to the initial weight pre-intervention. In humans, such experiments tend to be done on lean young males. What I get from these results is that if you remove a lot of the other factors at play, there is no doubt that all animals have an innate homeostatic system in place that maintains a relatively stable body size/composition. Perturb that system and it wants to return to baseline.
But I juxtapose this with my own experience. I am a genetically lean person. Not ectomorph skinny, but I am not genetically predisposed towards obesity or flab. I was a somewhat skinny kid and a late bloomer and I think my body probably would have wanted to be somewhere in the 120-130 lb range. And perhaps with the normal changes of aging, I imagine I'd probably weigh in the 130's now and not more than 150. Puberty spurt coincided with a bit more freedom and money in my pocket and I ate lunch at Burger King a few too many times. I "pudged" a bit over a year or so of doing this. I was always active playing various sports, etc. I believe my high weight was 139 which was far from obese but I was wearing size 11 jeans and having to buy 13's in one style was a shocker. (Yes, with size inflation, and the fact that these were juniors sizes, these pants would be too small for me today)
So what caused my shifted set point if it exists? My BK meals surely contained more calories than a usual lunch, but I wasn't stuffing my pie hole. Why did not my innate homeostatic mechanism just kick in and have me eat less at dinner? I think, based on his recent posts, Stephan Guyenet would make a food reward argument. But, although the diet my Mom fed me growing up was rather plain and simple, there were yummy things in the home that I could partake in especially when Mom went back to work part time around age 11. There's food reward to be found in that yummy white crystalline clover honey and butter on oatmeal bread!! Why didn't that reset my set point?
OK ... so I overreacted, went on rather a crash diet, and lost down to 105-110 lbs. Clearly below my original set point. I suppose the binge disorders that resulted were my body's way of fighting against me trying to maintain too low a weight. But why when I got to around 125 or even that 140 lb weight did my body not stop me from binging more? Spring semester of freshman year I binged my way up to ... gasp! ... around 165 lbs. I do not see how set point theory can mesh with this experience. And while many surely don't experience the same extremes, I would note that most of my classmates gained some weight that they did not take off until years later after graduation. If there's something about the college environment that resets the setpoint, why didn't everyone revert back to their thinner selves over the summer breaks? Those who did, like me to some extent, did so with deliberate efforts: aka going on a diet. Why would my body have reset my setpoint way up higher than I ever weighed before, and well above a "normal" weight for me?
Here is where this whole theory just falls apart for me. When I "sobered up" from my binge, why didn't my body just revert itself back to at least that 139-ish mark?
I agree with Flatt and those commenters who point out that the whole notion of shifting set points is inconsistent with the theory at its very basis.
Now on to settling point. Now this makes more sense to me because most people are relatively weight stable as adults. They may be obese or lean, but despite diet-mania and whack jobs like me who cycled wildly, most of my friends I've known through the years have not spent most of their adult lives gaining or losing weight, rather they weigh about what they weigh ... and perhaps a few pounds creep on over the years as we age, slow down (and this can simply be sedentary job to pay the bills!), etc. So most have a semi-homeostatic settling point at which they are in energy balance.
It would seem that our bodies don't have a great capacity to distinguish 40 extra pounds from 140 extra pounds in terms of "reserves". The "last 10" are always hard to lose b/c our bodies do seem to sense this small amount of excess -- if they see it as "excess" at all. But I think the body lets go of 20-30-40 lbs *relatively* easily but after that it sort of panics from sensing deficit for so long. I don't think our bodies realize we have perhaps another 20-30-40--100 lbs more in the tank!
I do find it interesting that -- although size/distribution is different -- I've probably spent the most time of my adult life weighing what I currently do. This used to be around my max weight backstop for all the yo yos pre-1997 Atkins stint. And it's about the weight I got down to in 2004 on stint 2. I spent most of 2009 and early 2010 trying to get away from this "settling point". I finally sort of gave up last summer. More just giving myself a break. So a year of not trying for the most part here and I'm hoping this means my body may be more willing to give up that excess weight when I make a new push.
In Part II, I'll address body composition and substrate balance issues in terms of this settling point concept. I'm not convinced by that argument and I'll go into the reasons why. But I am more open to the settling point concept in general than I am to a set point. Call it a "sweet spot", of which there can be several, for every body exposed to varying environments. And since I went into the personal stuff quite a bit, I will add that in my opinion, the whole diet mentality is an eating disorder in and of itself. I am interested in academic discussions of body weight regulation, and I agree with Kurt Harris that humans were not meant to count calories. For the human raised in a non-obesogenic environment or who for whatever reason remains lean through their 30th birthday, this may well be their "luck" to have an intact homeostatic system. But this system just seems so DARNED EASY to override. Be it being guilted into overeating (in my youth it was the starving kids in Ethiopia), societal/cultural pressures (My Big Fat Greek Wedding), body image issues (for me it was being more JLo/Fergie/Beyonce in the era of Cheryl Tiegs and Farrah), drinking or eating being integral to socializing, laziness in food selection ... etc.etc. -- it doesn't take much to throw it all off. And although I will not go so far as to say this has "damaged" the metabolism, it sure has thrown off the natural homeostasis. I consider myself lucky to have at least been able to re-establish a "sane" homeostasis at my current considerably reduced weight and size.