You could write a blog post twice a day about dietary pseudoscience and never come close to keeping up with the flood of bad reporting. This post is not about the study rather it will be a primer for a Dietary BS Detector. Teach you to fish rather than give you a fish yaada yaada. Plastic residue causing obesity was widely and credulously reported from multiple news media outlets this week. Skeptoid Episode #60 is a good example of this type of BS. There are variations on the story but one common theme emerges. Plastic residue is making children obese. My favorite example from the Daily Mail “Are chemicals in food packaging making children fat? Experts warn they expand waistlines and increase the risk of diabetes” So take out your skeptical tools (logic/science) and we will work through this pile of bad reporting together.
The first question you must ask about any dietary claim. Does it violate any laws of physics? I find this question weeds out a lot of useless claims immediately and allows you to move on. This article claims that eating plastic encapsulated food makes children obese. Basic laws of physics conservation of mass. You cannot gain a pound of weight without consuming at least that much weight in food or fluid. Since our bodies are not 100% efficient we have to consume much more than a pound to gain a pound. Calorie dense items translate a higher % of mass but it still cannot come close to 100% of mass or exceed it. There is no way that you could become obese by eating plastic since we have no real ability to metabolize it. If it was slowly impacted in our intestines without killing us you might gain a little weight. You would die from intestinal obstruction long before you would gain any real weight. It is physically impossible to gain significant weight by ingesting food packaging residue without killing yourself. Dietary pseudoscience often overplays the effects of nutrients/additives and how much it affects your body weight. You cannot gain 5lbs because you consumed an 12oz slice of cake no matter how calorie laden it is. You are not a plant you cannot absorb light and make more carbohydrates. Humans are not 100% efficient you will always eat or drink much more than you will gain. Simple equation burn more mass than you ingest you will lose, eat more than you burn you will gain. So plastic residue cannot affect your weight directly. This reporter’s claim fails to abide physics. That said, could it affect you indirectly by metabolism or satiety?
The plausible question is, does plastic residue affect metabolism? This article claims a link between insulin resistance and the chemical phthalate in the urine. It assumes that insulin resistance results in obesity(chicken or egg argument). Possibly true but not probable. This research is correlational not causal. Lets put on our logical fallacy caps here. What do we know about correlational studies? “Correlation does not imply causation. It is a phrase used in science and statistics to emphasize that a correlation between two variables does not necessarily imply that one causes the other Many statistical tests calculate correlation between variables. A few go further and calculate the likelihood of a true causal relationship. Correlation proves causation is considered a questionable cause logical fallacy in that two events occurring together are taken to have a cause-and-effect relationship. This fallacy is also known as cum hoc ergo propter hoc, Latin for “with this, therefore because of this”, and “false cause”. A similar fallacy, that an event that follows another was necessarily a consequence of the first event, is sometimes described as post hoc ergo propter hoc (Latin for “after this, therefore because of this”). Causation requires multiple independent lines of differing correlation research to draw any conclusion. A single correlational study says nothing about causation. The reporter and the researchers are drawing conclusions. The researcher’s are tentative and the reporter’s are definitive.
In this case, it is equally plausible to say that insulin resistance in children elevates phthalate in the urine. I don’t think that is true either, but given the findings it is just as plausible.
Question one-fail, question two singular correlation research. You could stop here. It is prudent to use one more skeptical tool. I use Occam’s razor. Is there a simple much more likely reason for obese children to have phthalate in their urine? Obese children have high rates of insulin resistance. How did they get high rates? Current consensus in pediatrics is there may be a genetic component, but obesity is the predisposing factor. How do children get to be obese? Conservation of mass again, they eat a lot of calorie dense food.
Pre-packaged food like cupcakes and snack cakes are wrapped in plastic. Prepared food such as bologna, processed cheese, even minimally processed meat and dairy have relatively high levels of phthalate. Obese children do not favor lean meat fresh fruits or vegetables.
Soooo if an obese kid has phthalate in his urine what is more likely as the cause of the obesity? Is it the food or the packaging? The food no question. The food doesn’t violate any law of physics. Doesn’t conflict with the findings of the study. It is the simplest best answer. Bing! BS detected. Three strikes and you are out in my book.
See you didn’t even have to critically review the study to figure this one out. Nailing dietary pseudoscience is as easy as 1 2 3.
What is implied by the reporter is that pizza doesn’t make you fat, the pizza box does.
FYI the researchers did not draw the same conclusions that the reporters did.
“The researchers said their findings don’t prove that eating food packaged with phthalates causes insulin resistance.
For example, it’s possible children who are already insulin-resistant have unhealthier eating habits and eat and drink more packaged products – thus the higher phthalate levels in their urine.”