David, thanks for the reply. I also appreciate respectful disagreement and I’m glad you feel the same. It’s always a little tenuous for me posting a critical viewpoint in a discussion on the internet cause of how easy it is to misconstrue when you don’t have body language and tonal cues. Anywho.
Absolutely agree that nutrition is complicated. In many ways I believe that we’re both right. I also really appreciate the fact that you exist on these forums because your views provide a nice contrast with a lot of the ideas here and I imagine that directly leads to better, more complete information for everyone.
I am critical of both your position and Matt’s. However, for me personally, many if not most of the things Matt says apply right now. I have been dieting nonstop pretty much since I hit puberty and have experienced almost all the symptoms he describes; when I started eating more food they got better. I used to always have to explain to the doctor that 98.6 was a fever for me because my normal body temperature was 97.0, and it only got higher when I was really sick. Now my temps have risen a full degree and sometimes more, depending on the whims of my ovaries. My blood pressure has risen, but it used to be too low (I’ve blacked out from standing up too fast) and now it’s low-normal, so I would call that an improvement. It all fits. You, on the other hand, obviously experienced negative effects from increasing your food intake and are experiencing positive effects from exercising more (right now, even moderately exercising makes me feel like I have the flu, but there are a bunch of reasons why that’s the case and I fully expect for it to change eventually). We’re naturally going to come at this from different angles because of our differing experiences. I think these opposing perspectives enable us to be especially critical of what the other is saying.
I spend a lot of time looking at the science on this, but I’m hesitant to attribute a giant bunch of expertise on myself. However in my somewhat informed opinion, it’s absurd to make a blanket statement about obesity being unhealthy for a couple of reasons. First off, BMI, around which all the correlative data is based, is a ridiculous and unreliable metric to use for assessing health. It’s just a ratio of weight to height. Your weight is comprised of fluids, organs, muscles, and bones as well as fat. The former four are about 70-90% of and individual’s weight. There is plenty of genetic variance among individuals when it comes to all of these, particularly bone structure and muscle mass. And both, especially muscle mass, are additionally affected by quality and quantity of exercise. Bone and muscle tissues are both much denser than fat and a genetic predisposition for having more of either or both is going to make that person much naturally heavier than another person with naturally less bone/muscle.
Also, from a statistical perspective, the “ideal weight range” is only going to be achievable by the median 50% of people. The remaining half will be distributed on either side of this range, forming a bell curve. Some of them may just be in the wrong category, but many of them will be exceptions to the rule for various reasons.
It is often suggested that, since fat is what we hate and what people have too much of, we should swap BMI for body fat percentage. That would have a number of advantages but herein lies the danger of conflating correlation with causation: if obesity is not a causative factor in the health problems to which it correlates, there are going to exist a sizable percentage of fat people who are also perfectly healthy. If those people are then advised that they must lose weight in the interest of their health, it is almost certainly going to result unfavorably for them. When you and your metabolism are both healthy, tinkering with it is the last thing it’s a good idea to do. And believe it or not, for all of the terribly unhealthy obese people, there are plenty of perfectly healthy ones.
I do agree with you that the correlation should not be ignored. But, as any decent scientist ought to know, correlation does not equal causation. It’s something of a mantra because it is so important to keep in mind when performing and interpreting research. I do not agree with you that the riddle of obesity is solved, and I do not think many scientists do either, although I know the opinion that it is simple is rampant in our society. (I will also point out that there is not to my knowledge any reason aside from conjecture to believe that Americans eat any more now than they always have. And I’m not sure that idea is actually testable because a scientific record of average calorie consumption from ~100 years ago would be necessary to compare to similar records from today, and I’m not sure such a record exists.)
It’s pretty obvious at this point that the usual suspect health problems are associated with having excess body fat, but the mystery that is as yet unsolved is HOW. There is no scientific evidence that I am aware of to show that excess body fat has a causative effect, and until that can be verified it is irresponsible to suppose that it does. It is my suspicion that the etiology of this cluster of diseases, including excess body fat, is not simple and linear, nor does it manifest the same way in all people. It’s a complex and difficult issue to study.
I have not seen the documentary you mention, although I will definitely be looking it up, but I do know that everyone (except anorectics who are a psychologically distinct minority) underestimates their caloric intake. When study participants are asked to self-report their intake, they consistently claim to eat 500-1000 fewer calories per day than scientists who closely monitor and record their intake find them to actually be consuming.
You’re probably right that there is a subsection of the obese population that got that way by eating too much food and can un-get that way by eating less food. However, there are usually a lot of complex biochemical mechanisms that were involved in them overeating and need to be addressed to effectively reduce their intake without damaging metabolism, and the interplay of these mechanisms is not actually well-understood. This does not mean that some people cannot cut their calories without adversely affecting their metabolism, but it does mean we haven’t much way of knowing if it will.
You say you don’t think deprivation diets and their negative effect on metabolism explains the obesity epidemic. I would agree with that statement in a broad context–it certainly does not, any more than does the equally simplistic supposition that the epidemic can be explained entirely by a hypothetical nationwide increase in caloric intake. However, I do believe that the metabolic impact of irresponsible dieting is a factor that has a strong influence in certain populations. There are almost certainly many causative factors that all work together to explain the obesity epidemic: yo-yo dieting is but one, and widespread changes in food intake is very likely another. I also think that your observation about decreasing physical activity levels is spot on and is probably a more major factor than either of the above two. That’s my opinion, anyway.
I’m confused on your point about larger people and BMR, but it appears to me like we’re describing two different things as if they’re the same. Assuming my metabolic rate is suboptimal to begin with, if I stay the same size and it goes up, the net result is an improvement in my overall health. My cells are able to produce more ATP and my body no longer has to prioritize on its processes as a result, because it can run all of them at full steam. If, however, I gain weight and my metabolic rate increases only in proportion to that weight gain, as in, exactly enough to fuel the extra body mass I’ve accumulated and no more, then effectively it hasn’t changed at all, although on paper my caloric expenditure will be higher. These two things can both be described as “an increase in BMR,” but they’re really two separate phenomena. Does that make sense?
As for measuring temperature to determine if BMR is or is not suboptimal, I am under the impression that the way to make it a suitably reliable metric is to consistently measure it in the morning just upon awakening so as to control for most of the other factors that can cause it to otherwise fluctuate. Over a short period of time, that measurement can reliably tell you if your body is conserving energy or not. Could you elaborate on why, under these specific conditions, you believe temperature to be unsuitable as a metric?
I would never dispute the benefits of exercise with you. I think the vast majority of people should exercise unless they have a medical contraindication.
I believe I misspoke at the end of my last post when I said that exercise has the certain biochemical effect of energizing an individual as opposed to relaxing them. It was an oversimplification and I should know better than to make those; it can do either or both of these things depending on the individual and the circumstances of the exercise.
I wonder about your theory. It also seems like an oversimplification, but it’s also intriguing the way you compare the neurochemical effects of nutrient saturation with exercise. Have you done much research into the specific chemical mechanisms involved, or are you just generally speculating based on experience? (Not that there’s anything wrong with general speculation based on experience. Just curious.)
