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Interesting example with your shyness de-training.
Indeed, comparitive research in psychobiology suggests that while behaviors can be transiently altered, cytoarchitectural changes in brain biogenic amine systems tend to remain the same after critical time periods (this most often seen in monkeys who are socially isolated after birth and then taught to engage in social behaviors).
You know it gets me hot when you talk like this.
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However, and let me just throw out some heavy ass bullshit here, in the context of dyadic relationships and appropros time in therapy we have seen (in contemporary psychoneuroendocrinological literature) some possibility of changing this cytoarchitecture, suggesting some plasticity of the brain (the adolescents are all past the 'critical period' point).
The key word there is possibility and some. I'm not denying that it is *possible*. I'm saying it takes extensive work and effort. I don't think you'll disagree with me on either. Also, plasticity of the brain probably depends heaviliy on what part of it your'e talkign about. Different structures may retain relaively more or less plasticity depending on the relative benefits of such. In what I've seen looking at bodyweight and the hypothalamus, the plasticity isn't really there (unless you're talking about adjusting setpoint upwards). Might other areas of the brain (cf. if someone loses a given senese in an accident and others improve to take over for it) show more plasticity? Sure. But it's not generalizable (IMO) across the entire brain.
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Furthering this to our current conceptualization. A set point is biologically set, but like the dyadic relationhship and its importance in hardening emotional regulatory predispositions, it is vulnerable to social stimuli (in this case food eating behavior). Somewhere in the arcuate nucleus changes could occur in the number of leptin responsive cell beds due to chronic firing (POMC-CART [less leptin needed to fire] NP-Y/AgRp [less leptin needed to inhibit]) due to severe underfeeding and then overfeeding (e.g., a 'learning' or 'molding' process. Perhaps drastic drops in leptin (underfeeding) coupled with a transient spike in leptin, suggesting acute 'okay periods' may cause functional changes in the cell groups which then affect the PVN and other central and peripheral tissues downstream. Such changes would decrease what was originally considered a heretofore 'normal' leptin mediated arcuate-pvn response, thus affecting feeding behavior and hence adipose tissue (the thermostat is changed). This process would occur over a period of sustained time and require similar behavior to 'buttress' the response; with chronic 'regulated' eating patterns, this cell group change would then re-modify back to a different structure.
And in everything I've seen to date (usually looking at some en point like metabolism), it just doen'st happen. I know of at least one study that monitored post-obese dieters for something like 2 years (and they kept the weight off). Metabolism did not recover. Now, is it possible taht it occurs over longer periods? I suppose. 5 eyars, 10 years perhaps setpoint comes back down. For 99% of dieters (who will regain the weighht within a year or two), that's effectively saying it never happens. Of course, bodybuidlers and psycho athletes aren't 99% of dieters.
Empirically, folks who get and stay lean do seem for extended periods do seem to have a relatively easier time of doing it. But you have to ask if that's an actual change in setpoint dynamics or if it's simply a permananceafying (making permanent, if you can make up words like dyadic, I can make up words too) of BEHAVIOR PATTERNS. I suspect the latter. The behaviors that keep them lean, training intensely, monitoring diet become habit. But I doubt that true biological setpoint has come down. Data from the Natinoal Weight Control Registry would seem to bear this out. Those folks have lost weight and kept it off for extended periods but they show many consistent BEAHVIOR PATTERNS. One of them is continuing to restrict calories, maintaining activity, monitoring changes in weight (to see if they are falling off the wagon). I would expect studies (to my knowledge they haven't been done) to show that they are still showing signs of a depresed metabolism and the rest (i.e. metabolic rate below what would be predicted for bodyweight, as is common in post-obese individuals).
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As you said and I agree (duh), the body seeks homeostasis. Wouldn't this be one way to achieve it (at the primary level rather than the secondary--central structure [brain] versus periperhal tissue [adipose]?
But you have to ask yourself if it's adaptive or not. Within the context of bodyweight, it's generally not going to be adaptive for the body to 'learn' to maintain a lower bodyweight because that prediposes you towards death when/if the next famine comes. Biologiclaly, it's adaptive to be fat (up to a point) and maladaptive to be lean. Which is why the system evolved in the assymetric way it did (generally easy to get fat, hard to get lean). Millions of years of evolution shouldn't be able to be undone by 2 years of staying lean.
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---->Thus could a sustained eating style (dysregulated by 'human' standards) allow for a modification of set-point partitioning as long as that style is maintained. Drawing from my initial example, if a monkey is taken from a socialized environment, and subjected to severe social deprivation or even change, plasticity of brain structure is revealed, contigent upon the nature-nurture interaction.
I suspect that how will this works depends a lot on the age of the animal. As above, genralizing brain plasticity from something like behavior to bodyweight is a dangerous proposition. All parts of the system don't necessarily show the same adaptability or plasticity.
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On a completely unrelated note (at least now). If the overfeeding portion of this plan is EXTREMELY fat-free (i.e., >30g/fat), would not this make it extremely hard to 'rebound' from an adipostat perspective due to the extremely energy-inefficient process of DNL, both hepatically and in adipose tissue?
Do note that one of the conditions where DNL capacity upregulates is in the context of extremely low fat (>10% fat) diets. There's still probabyl some energetic efficiency but Acheson's massive carb-overfeeding studies shoed that with several days of super high carbs (700-900 g/day over 5 days or so), you can make plenty of TG.
Lyle