I love the way Lyle McDonald writes his books (yes, I am promoting it,
), he puts a rather complicated subject which can not deal perfectly with "absolutes", while giving you a "general" understanding that is grounded in education/study/research (etc), and writes it in a way the general population can "understand" (this is KEY):
For the sole purposed of this topic, I am going to post Chapter 9, of the book I purchased some time back called: The Rapid Fat Loss Handbook (2.0.)
by Lyle McDonald, if this is not permissible let me know, and I will take care of it :
Chapter 9: Metabolic slowdown and what to do about it
The next issue I want to talk about is that of metabolic slowdown on a diet.
Once again, this is one of those hideously complicated topics that one day, I should write an entire book about.
In this booklet, you’re getting the very abbreviated version.This chapter will also act as a bridge for me to talk about what may be the single most important supplement on the crash diet as well as acting as a bridge for the next chapters.
Body weight regulation
Decades of research have led to one rather depressing conclusion: human body weight is regulated.
Now what does that mean? To explain it I’m going to use the rough analogy of a thermostat which acts to regulate the temperature of your house. So you set the thermostat at 70 degrees. Now, the thermostat has a meter in it that tells it what the actual temperature of the house is; if the temperature falls below 70, the heat comes on, if temperature goes above 70, the air conditioning comes on.
The human body acts similarly but, in this case, the regulator is the hypothalamus (a structure in your brain) and things such as metabolic rate, hunger, activity levels and hormones are what change when you gain and lose weight. So the hypothalamus is keeping track of your bodyweight (more
accurately, how much body fat you are carrying) and also manages to track how much you’re eating (I’ll explain how in a second).
For the most part, your body wants to keep you where you are at body weight/body fat wise. So when you start dieting, eating less and losing body weight, your hypothalamus senses it and your body slows metabolism, increases your hunger/appetite levels, and alters hormone levels in a generally negative fashion.
To a much lesser degree, when you overeat and start gaining weight, your hypothalamus increases metabolic rate, decreases your hunger/appetite, and ramps up certain hormones.
As I discuss in much more detail in my booklet Bromocriptine the system is very asymmetrical and the human body generally defends against weight loss far better than it does against weight gain.
Basically, it’s much easier for most people to gain weight than to lose it. There are a small percentage of people who have trouble gaining weight but they are in the minority.
How the body does this: the very, very short course
Explaining the systems involved in body weight regulation would truly take a book and all I really want to say is that there are a number of hormones including leptin, insulin, ghrelin, peptide YY (some of which you may have heard of and others you’ll think I’m making up) and others that ‘tell’ your
hypothalamus both how much you’re eating and how much body fat you’re carrying.
All of these hormones respond both to food intake and how much weight/fat you have on you and act as the signals which tell the brain what’s going on so that it can make adjustments. A much more detailed description of this system is found in either my Bromocriptine booklet or in The Ultimate Diet
2.0. But, unless you’re just interested, you really don’t need to know the details.
So when you start a diet, eating less and losing weight, your body notices it and starts to adjust metabolism downwards. Appetite/hunger tend to go up and many hormones change. In essence, this is the ‘starvation response’ that everybody tends to talk about. Metabolism (and weight/fat loss) slow
and you get so hungry that you tend to break your diet, frequently eating so much that you put the weight you lost right back on.
I should mention right here that the degree to which this occurs depends a lot on the level of leanness (there are other factors but I don’t want to get into the details here).
Meaning that someone at 10% body fat will tend to have far greater issues with this than someone who is at 40% body fat. Keep this in mind as it helps to explain the differences in frequency of free meals, refeeds and full diet breaks (next chapters).
Metabolic rate reduction: the body weight component
First let me mention that there are two distinct components to the drop in metabolic rate. The first is simply a function of losing body weight. I haven’t talked much about metabolic rate but the amount of calories you burn both at rest and during daily activity tends to be related directly to your body weight: a heavier individual burns more calories than a lighter individual both at rest and during activity (if you don’t believe me, try walking a mile with a 20 pound backpack on and see how much harder it is).
So as you lose weight, your energy requirements go down.
On which note, I’ve wondered for a while if it wouldn’t be a good dieting strategy to use a weighted vest or backpack to maintain your ‘effective’ body weight, that is replace the lost body weight with weight on the vest/backpack to try to maintain daily caloric expenditure.
The effect wouldn’t be monstrous, mind you, as wearing the pack would only affect calorie burn during activity (not rest) but every little bit can help at the end of a diet. It’s also nice feeling bulletproof because of the weighted vest you’re wearing. You will get funny looks from people.
Obviously, short of my backpack/vest idea, there’s not much you can do about this component (other than get fat again); if you’ve reduced your body weight, you will have reduced the number of calories your burn each day because of it. This is another potential role for exercise, especially at the end of the diet, helping to compensate for the reduction in calorie expenditure that occurs as a consequence of losing weight.
Metabolic rate reduction: the adaptive component
But in addition to the reduction in caloric expenditure due solely to weight loss, there is another component called the ‘adaptive component’. It’s existence has been debated over the years with some studies saying it exists and others not.
So what is an adaptive component anyway? In this context it means that the body has reduced (in the case of dieting) or increased (in the case of overeating) caloric expenditure more than you’d expect based on the change in body weight.
That is, say that a reduction in weight of 10 lbs would be predicted to lower daily calorie expenditure by 150 calories, but when you measure it, the reduction is actually 250 calories. That extra 100 calories/day reduction is the adaptive component. I want to mention that the adaptive metabolic
rate is never sufficient to completely eliminate weight loss, it simply reduces the effective daily deficit (which may slow weight loss). Perhaps the largest reduction in metabolic rate recorded is on the order of 30% (and that was seen in relatively lean men who underwent semi-starvation for months).
Considering that the daily deficit on the crash diet will be 50% or more of daily energy expenditure, the slowing of metabolic rate will not be able to eliminate weight/fat loss, only slow it.
I should mention that the adaptive component tends to be quite variable and several factors affect it. One is body fatness, generally the fatter you are, the less of a problem it is. Tangentially, this probably explains why some studies don’t find an adaptive component, they are looking at extremely obese individuals.
Gender also has an effect,
women’s bodies tend to fight back harder and faster than men’s (see my booklet Bromocriptine for more details on this), dropping metabolic rate more than men (this is one of several reasons men typically lose weight and fat faster than women).
There is also good old genetic variability, some people’s bodies seem to fight back harder and faster than others.
Generally, the people who gain weight the easiest lose it the slowest and vice versa. And what causes the adaptive component? Primarily the hormones I mentioned above.
Actually, not so much those hormones as the systems that they control such as nervous system output, thyroid hormone, and a couple of others. Although you’ve probably read that levels of thyroid hormone are the primary regulator of metabolic rate, this is an altogether simplistic explanation (even for this booklet).
Rather it’s an integrated response to decreased nervous system output (which is often below normal in obesity to begin with, a metabolic ‘defect’ if you will), thyroid hormone (which may be low to begin with), leptin, insulin and others. When you diet, it simply turns out that all of those systems decrease below normal, causing the adaptive decrease in metabolic rate.
However, the different systems (the main ones I’m going to focus on here are nervous system output and thyroid) have different effects over different time frames. Thyroid, for example, is a fairly long-term hormone. Its effects can be seen for 3-4 weeks before anything major changes (I should note that thyroid also has somewhat minor, short-term effects on metabolic rate).
In the short-term, a few days to a few weeks of dieting, the main system that is decreasing metabolic rate is a decrease in sympathetic nervous system (SNS) output. In fact, within 3-4 days of extreme dieting, SNS output can and will drop, lowering metabolic rate slightly. As well, SNS output and thyroid levels are synergistic, they make each other work better; the drop in SNS output means that thyroid hormones won’t have as great an effect as you’d expect.
Since the crash diet is mostly short-term only (the only people who might stay on it longer than a few weeks are category 3 dieters for whom the adaptive component isn’t as big of a deal in the first place), the only system we are going to concern ourselves with is SNS output. Since, short of using thyroid drugs (or hoping that one of the thyroid boosting supplements on the market actually works) you can’t do anything about thyroid anyhow (well, see next chapter), there’s nothing to be gained worrying about it.
================================================================================================================
And he goes on to tell what to do about it.........
If you are really interested in dealing with some weight loss "issues", and want to learn some of the (fluff) behind the reasoning with some of his dieting approaches, then purchase his books. He takes a great deal of time explaining the physiology behind certain complications, and it is time well spent.
Chillen
