A Philosopher's Blog

Gluten, Celebrity Diets and Critical Thinking

Posted in Medicine/Health, Reasoning/Logic by Michael LaBossiere on December 5, 2011
Oat grains in their husks

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Having been around a while, I have seen celebrity endorsed fad diets come and go. One of the most recent trends is the gluten-free diet. This diet has been presented as a way of losing weight and some have even suggested that it can help with autism. While various celebrities have promoted this diet, health advice from celebrities should be subject to proper critical assessment.

As might be imagined, people have a tendency to confuse celebrity status with expertise. That is, people often believe what a celebrity claims is true because the celebrity is famous. However, while reputation is a factor in assessing expertise, the reputation has to be within the field in which the person is making the claim. So, for example, a person’s fame as an actor has no relevance to her ability to make credible claims about diets. There is also the fact that a person’s expertise depends primarily not on their fame but on such factors as education, experience, and  accomplishments within the field. A lack of excessive bias is also an important factor in assessing the claims of an expert.  Accepting claims based on unwarranted authority (such as buying into a diet simply because a celebrity endorses it) would be to fall victim to a fallacious argument from authority.

Relying on experts is not, of course, a fallacy. However, one has to be careful to turn to the right experts-that is, people who have the knowledge and experience to be be able to make informed claims and who have the objectivity and lack of bias to be trustworthy. As might be imagined, celebrities who are pushing specific products would tend to be lacking in both areas.

As a specific example, consider the fad of gluten free diets. Like some fad diets, there is some truth behind the fad.  In the case of gluten, there is a condition called Celiac Disease. People with this disease need to have a gluten free diet in order to avoid various health problems.  While this is a real condition, only about 1% of the US population has Celiac Disease. As such, 99% of the population does not need a gluten free diet.

However, those pushing a gluten free diet claim that it has health benefits for people who do not have this disease. If so, then the diet would be worth considering. However, there seems to be no objective scientific data supporting these claims-thus there would seem to be no reason for people who lack the disease to go on such a diet.

But, one of the main reasons for going on a diet is weight loss and the gluten free diet has been pushed as a means of losing weight.  However, the evidence is that the gluten free diet has no special capacity to cause weight loss. See, for example,  Wendy Marcason’s “Is the Evidence to Support the Claim that a Gluten-Free Diet Should Be Used for Weight Loss”, page 1786 in in the November 2011 Journal of the American Dietetic Association.

As has long been known, weight loss is primarily a matter of expending more calories that you take in. While gluten products do have calories, gluten calories are simply calories-as are non-gluten calories. In fact, as Marcason points out, some gluten free products have more calories and fat than their gluten containing counterparts. Eating such products in favor of the lower calorie versions will, obviously enough, not promote weight loss.

From the standpoint of thinking well about these matters, there are three main points to take away from this. First, celebrities are not (unless they are also health experts) experts on dieting and health. Second, advice about dieting should be sought from the actual experts-who are generally not celebrities and who tend to give mundane advice like “eat less, eat better and exercise more”. Third, losing weight is a matter of expending more calories than one takes in and there is obviously no fad diet that can change this basic equation. Naturally, a good diet is also more than just a matter of calories-there is also the rather critical matter of nutrients (ironically, there are people who are both obese and malnourished at the same time).  But, do not take my word for it-listen to the experts.

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5 Responses

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  1. T. J. Babson said, on December 5, 2011 at 4:24 pm

    “Relying on experts is not, of course, a fallacy. However, one has to be careful to turn to the right experts-that is, people who have the knowledge and experience to be be able to make informed claims and who have the objectivity and lack of bias to be trustworthy.”

    This is not easy when it comes to nutrition, because a lot of the science is of very poor quality. For example, I don’t believe there is any truly reliable information about how many carbohydrates per day one should consume.

    • Michael LaBossiere said, on December 5, 2011 at 9:38 pm

      Diet science (like all sciences) seems to be in an endless state of revision. There is also the fact that the diet guidelines that are issued by the state are influenced by lobbyists and by other non-scientific factors.

      However, I’ll tend to go with the best science of the day, tempered by my experience and some critical thinking.

  2. magus71 said, on December 5, 2011 at 6:07 pm

    Mike, what is an expert? I’ve looked at tons of studies and read a lot on the subject but have no certificates to prove it. I do believe I have some insights that are better than Dr. Oz’s.

    Diet for weight control comes down to these factors:

    1) Calories
    2) Macronutrients (fat, carbs, protein)
    3) Micronutrients (vitamins, minerals etc)

    Calories are still king but are not a perfect measure of a diet’s effectiveness. The importance of calories have been massively understated in the new diet age. The trick is to find diets that make us want to consume less calories. This is usually accomplished via two vectors: 1) Volume: Our stomachs want to feel full. Eat foods that are voluminous. 2) Eat foods that minimize insulin spike. More insulin equals more hunger.

    The gluten free diet has become quite a rage.

    TJ, the most sensible diet I’ve ever seen is called the “S Diet”. I have never had a problem with weight control, but I do think that as we age, how we control calorie intake becomes more and more important. The S Diet is on Amazon and comes down to this:

    1) Three meals a day, no seconds, no deserts and little to no refined sugar on weekdays.

    2) On weekends eat what you want.

    The effects of carb consumption is heavily influenced by physical activity. The more activity and the more intense the more carbs can be tolerated without weight gain. Sugar is the enemy. Carbs, if consumed in a natural state ie whole fruit, not juice, are not too bad.

    Mark Sisson has a degree in biology, and is a medical physician who’s in outstanding shape. He recommends the following for carb intake:


    • Michael LaBossiere said, on December 5, 2011 at 9:41 pm

      Description of Appeal to Authority

      An Appeal to Authority is a fallacy with the following form:

      Person A is (claimed to be) an authority on subject S.
      Person A makes claim C about subject S.
      Therefore, C is true.

      This fallacy is committed when the person in question is not a legitimate authority on the subject. More formally, if person A is not qualified to make reliable claims in subject S, then the argument will be fallacious.

      This sort of reasoning is fallacious when the person in question is not an expert. In such cases the reasoning is flawed because the fact that an unqualified person makes a claim does not provide any justification for the claim. The claim could be true, but the fact that an unqualified person made the claim does not provide any rational reason to accept the claim as true.

      When a person falls prey to this fallacy, they are accepting a claim as true without there being adequate evidence to do so. More specifically, the person is accepting the claim because they erroneously believe that the person making the claim is a legitimate expert and hence that the claim is reasonable to accept. Since people have a tendency to believe authorities (and there are, in fact, good reasons to accept some claims made by authorities) this fallacy is a fairly common one.

      Since this sort of reasoning is fallacious only when the person is not a legitimate authority in a particular context, it is necessary to provide some acceptable standards of assessment. The following standards are widely accepted:

      The person has sufficient expertise in the subject matter in question.

      Claims made by a person who lacks the needed degree of expertise to make a reliable claim will, obviously, not be well supported. In contrast, claims made by a person with the needed degree of expertise will be supported by the person’s reliability in the area.

      Determining whether or not a person has the needed degree of expertise can often be very difficult. In academic fields (such as philosophy, engineering, history, etc.), the person’s formal education, academic performance, publications, membership in professional societies, papers presented, awards won and so forth can all be reliable indicators of expertise. Outside of academic fields, other standards will apply. For example, having sufficient expertise to make a reliable claim about how to tie a shoe lace only requires the ability to tie the shoe lace and impart that information to others. It should be noted that being an expert does not always require having a university degree. Many people have high degrees of expertise in sophisticated subjects without having ever attended a university. Further, it should not be simply assumed that a person with a degree is an expert.

      Of course, what is required to be an expert is often a matter of great debate. For example, some people have (and do) claim expertise in certain (even all) areas because of a divine inspiration or a special gift. The followers of such people accept such credentials as establishing the person’s expertise while others often see these self-proclaimed experts as deluded or even as charlatans. In other situations, people debate over what sort of education and experience is needed to be an expert. Thus, what one person may take to be a fallacious appeal another person might take to be a well supported line of reasoning. Fortunately, many cases do not involve such debate.

      The claim being made by the person is within her area(s) of expertise.

      If a person makes a claim about some subject outside of his area(s) of expertise, then the person is not an expert in that context. Hence, the claim in question is not backed by the required degree of expertise and is not reliable.

      It is very important to remember that because of the vast scope of human knowledge and skill it is simply not possible for one person to be an expert on everything. Hence, experts will only be true experts in respect to certain subject areas. In most other areas they will have little or no expertise. Thus, it is important to determine what subject area a claim falls under.

      It is also very important to note that expertise in one area does not automatically confer expertise in another. For example, being an expert physicist does not automatically make a person an expert on morality or politics. Unfortunately, this is often overlooked or intentionally ignored. In fact, a great deal of advertising rests on a violation of this condition. As anyone who watches television knows, it is extremely common to get famous actors and sports heroes to endorse products that they are not qualified to assess. For example, a person may be a great actor, but that does not automatically make him an expert on cars or shaving or underwear or diets or politics.

      There is an adequate degree of agreement among the other experts in the subject in question.

      If there is a significant amount of legitimate dispute among the experts within a subject, then it will fallacious to make an Appeal to Authority using the disputing experts. This is because for almost any claim being made and “supported” by one expert there will be a counterclaim that is made and “supported” by another expert. In such cases an Appeal to Authority would tend to be futile. In such cases, the dispute has to be settled by consideration of the actual issues under dispute. Since either side in such a dispute can invoke experts, the dispute cannot be rationally settled by Appeals to Authority.

      There are many fields in which there is a significant amount of legitimate dispute. Economics is a good example of such a disputed field. Anyone who is familiar with economics knows that there are many plausible theories that are incompatible with one another. Because of this, one expert economist could sincerely claim that the deficit is the key factor while another equally qualified individual could assert the exact opposite. Another area where dispute is very common (and well known) is in the area of psychology and psychiatry. As has been demonstrated in various trials, it is possible to find one expert that will assert that an individual is insane and not competent to stand trial and to find another equally qualified expert who will testify, under oath, that the same individual is both sane and competent to stand trial. Obviously, one cannot rely on an Appeal to Authority in such a situation without making a fallacious argument. Such an argument would be fallacious since the evidence would not warrant accepting the conclusion.

      It is important to keep in mind that no field has complete agreement, so some degree of dispute is acceptable. How much is acceptable is, of course, a matter of serious debate. It is also important to keep in mind that even a field with a great deal of internal dispute might contain areas of significant agreement. In such cases, an Appeal to Authority could be legitimate.

      The person in question is not significantly biased.

      If an expert is significantly biased then the claims he makes within his are of bias will be less reliable. Since a biased expert will not be reliable, an Argument from Authority based on a biased expert will be fallacious. This is because the evidence will not justify accepting the claim.

      Experts, being people, are vulnerable to biases and predjudices. If there is evidence that a person is biased in some manner that would affect the reliability of her claims, then an Argument from Authority based on that person is likely to be fallacious. Even if the claim is actually true, the fact that the expert is biased weakens the argument. This is because there would be reason to believe that the expert might not be making the claim because he has carefully considered it using his expertise. Rather, there would be reason to believe that the claim is being made because of the expert’s bias or prejudice.

      It is important to remember that no person is completely objective. At the very least, a person will be favorable towards her own views (otherwise she would probably not hold them). Because of this, some degree of bias must be accepted, provided that the bias is not significant. What counts as a significant degree of bias is open to dispute and can vary a great deal from case to case. For example, many people would probably suspect that doctors who were paid by tobacco companies to research the effects of smoking would be biased while other people might believe (or claim) that they would be able to remain objective.

      The area of expertise is a legitimate area or discipline.

      Certain areas in which a person may claim expertise may have no legitimacy or validity as areas of knowledge or study. Obviously, claims made in such areas will not be very reliable.

      What counts as a legitimate area of expertise is sometimes difficult to determine. However, there are cases which are fairly clear cut. For example, if a person claimed to be an expert at something he called “chromabullet therapy” and asserted that firing painted rifle bullets at a person would cure cancer it would not be very reasonable to accept his claim based on his “expertise.” After all, his expertise is in an area which is devoid of legitimate content. The general idea is that to be a legitimate expert a person must have mastery over a real field or area of knowledge.

      As noted above, determining the legitimacy of a field can often be difficult. In European history, various scientists had to struggle with the Church and established traditions to establish the validity of their discliplines. For example, experts on evolution faced an uphill battle in getting the legitimacy of their area accepted.

      A modern example involves psychic phenomenon. Some people claim that they are certified “master psychics” and that they are actually experts in the field. Other people contend that their claims of being certified “master psychics” are simply absurd since there is no real content to such an area of expertise. If these people are right, then anyone who accepts the claims of these “master psychics” as true are victims of a fallacious appeal to authority.

      The authority in question must be identified.

      A common variation of the typical Appeal to Authority fallacy is an Appeal to an Unnamed Authority. This fallacy is also known as an Appeal to an Unidentified Authority.

      This fallacy is committed when a person asserts that a claim is true because an expert or authority makes the claim and the person does not actually identify the expert. Since the expert is not named or identified, there is no way to tell if the person is actually an expert. Unless the person is identified and has his expertise established, there is no reason to accept the claim.

      This sort of reasoning is not unusual. Typically, the person making the argument will say things like “I have a book that says…”, or “they say…”, or “the experts say…”, or “scientists believe that…”, or “I read in the paper..” or “I saw on TV…” or some similar statement. in such cases the person is often hoping that the listener(s) will simply accept the unidentified source as a legitimate authority and believe the claim being made. If a person accepts the claim simply because they accept the unidentified source as an expert (without good reason to do so), he has fallen prey to this fallacy.

      As suggested above, not all Appeals to Authority are fallacious. This is fortunate since people have to rely on experts. This is because no one person can be an expert on everything and people do not have the time or ability to investigate every single claim themselves.

      In many cases, Arguments from Authority will be good arguments. For example, when a person goes to a skilled doctor and the doctor tells him that he has a cold, then the the patient has good reason to accept the doctor’s conclusion. As another example, if a person’s computer is acting odd and his friend, who is a computer expert, tells him it is probably his hard drive then he has good reason to believe her.

      What distinguishes a fallacious Appeal to Authority from a good Appeal to Authority is that the argument meets the six conditions discussed above.

      In a good Appeal to Authority, there is reason to believe the claim because the expert says the claim is true. This is because a person who is a legitimate expert is more likely to be right than wrong when making considered claims within her area of expertise. In a sense, the claim is being accepted because it is reasonable to believe that the expert has tested the claim and found it to be reliable. So, if the expert has found it to be reliable, then it is reasonable to accept it as being true. Thus, the listener is accepting a claim based on the testimony of the expert.

      It should be noted that even a good Appeal to Authority is not an exceptionally strong argument. After all, in such cases a claim is being accepted as true simply because a person is asserting that it is true. The person may be an expert, but her expertise does not really bear on the truth of the claim. This is because the expertise of a person does not actually determine whether the claim is true or false. Hence, arguments that deal directly with evidence relating to the claim itself will tend to be stronger.

    • T. J. Babson said, on December 6, 2011 at 7:12 am

      Thanks, Magus. I just bought Sisson’s book.

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