David: I’m not trying to just be like “you’re wrong about everything!” here, and I certainly wouldn’t dispute that you’ve found something that’s working well for you personally (and could work well for others), but there are a few ideas that look quite wrong to me in your initial post:
First, I don’t know why you expect to see similar improvements when taking thyroid hormone or stimulants as when overfeeding. For your metabolic processes to function correctly, dozens of hormones need to be on the same page.
Stimulants just flood the body with catecholamines, inducing what essentially amounts to a prolonged fight-or-flight response during which the body is placed on high alert. This causes a temporary increase in certain metabolic processes, but that particular hormonal event in your body isn’t favorable to your BMR in the big picture sense.
Thyroid medication is generally one specific hormone. It’s an important one in determining BMR, but if your body is already making enough of it, then taking it is pointless at best; dangerous and harmful at worst. Either way, it isn’t going to do anything for your BMR, which could still be low as it is not solely determined by the amount of T4 present in your body.
In fact I find it odd that you expect these wildly different drugs to produce the same effect in your body. Perhaps you know something that I do not.
Insufficient caloric intake is medically known to slow down the BMR as the body goes into starvation mode. What constitutes “insufficient calorie intake” is somewhat up for debate as it depends on the individual and about a million biochemical factors, but the most conventional of conventional scientists/doctors will tell you that this is the case at some point of calorie deprivation. It should be fairly obvious that this point exists.
From there, we get the “overfeeding raises BMR” idea. If eating too little prompts the body to lower BMR, eating too much will prompt the body to raise it again, back up to the point where all bodily systems are functioning optimally. It’s like being a millionaire versus living paycheck to paycheck, at the cellular level.
Also, larger people don’t have higher BMRs adjusting for size. (If they did, tall people would all be way the hell healthier than short people.) It’s proportional. This is like how if your income is just enough to support you comfortably but then you go and have five kids, you aren’t going to be able to afford the same lifestyle with that income. You will need to increase your income in order to maintain it. That increase in income does not translate to you actually having more money in your pocket.
You’re right about foods and neurochemical response. That’s a thing. But honestly from what I understand, the neurochemical response varies based on how much your body feels it wants the food. Have you ever tried to eat dessert when you were absolutely stuffed and just gotten no satisfaction out of it whatsoever?
It’s worth noting that food causes the pleasant neurochemical effects that you describe because it’s supposed to. It’s not a “drug effect” in some sort of weird unnatural way. And normal eating does this; overeating will not do this unless you’ve got some sort of energy imbalance, in which case it triggers your parasympathetic nervous system hardcore because your body needs to get shit done on that front that it hasn’t been able to previously.
You’re also right about exercise triggering a feely-goody neurochemical response though, but to my knowledge it’s kind of the opposite in that it revs you up rather than relaxes you. Both are obviously good and necessary for health, but they’re not really the same.
Others have somewhat covered this point already, but: I don’t believe Matt is advocating overfeeding on a long term basis. It’s supposed to be a very temporary solution to kick-start your metabolism following deprivation. He’s just advocating meeting your body’s energy requirements with adequate amounts of food, which if done all along will prevent any need to tinker with metabolic rate at all.
I don’t think the metabolism can be raised anymore past a certain point. The cells can only churn out ATP so fast and there are a finite number of biochemical processes for it to go toward. (The inverse is also true: there are a number of vital functions, all requiring energy, that must be carried out if you are to stay alive.) Overfeeding in that sense is taking in more calories than your body can actually use in any way, and if the metabolic rate is already optimal, there’s just no need whatsoever to do this. It will also probably become a pretty unappealing prospect in this situation.
Overall, I guess I disagree with your hypothesis primarily on the grounds that overfeeding and exercise have opposite chemical effects in the body. But if you wanted to say that sometimes eating more is absolutely not the solution to a person’s problem and that sometimes exercising more absolutely is the solution, I would have to completely agree.
Would love to hear your thoughts.