The fitness industry is chock full of experts. There are gurus of all sorts doling out advice on exercise, weight loss, nutrition and other topics through books, websites, fitness facilities and various other products and services. There is no shortage of advice on any fitness topic, but there is a shortage of evidence to support much of this advice.

Many experts in the field feel their credentials (degrees, certifications, etc.) and their experience are enough to support any claim they make to their customers. We disagree. We feel that no matter an expert’s educational background or number of years in the industry, evidence must be provided to support every piece of advice that is given.

One of our goals when writing SPEED was to help set a better standard of quality in the weight loss and fitness industries. The majority of our time was spent researching what has really proven to be true about effective weight loss techniques. Admittedly, we were surprised by the evidence we found regarding some topics and we were forced to change our minds! We hope you appreciate the effort we put into supporting our recommendations.

We were pleased to see John Barban include a section regarding logical fallacies on his website. In fact, he has a rule set for participating in discussions which includes never using any fallacious arguments. We included a chapter regarding evidence in SPEED which also discusses some fallacious arguments that we see far too often in the weight loss industry. We feel it’s important for you to understand these fallacies in order to weed out the good information from the bad – and trust us, there’s a lot of bad. Below is our short section on  logical fallacies from SPEED. If you recognize one of these fallacies being used by someone, back away slowly and call for help as soon as possible.


Ad Hominem

Ad hominem is described as an argument that attacks a person, rather than the argument the person is making. This often happens when an opponent has no way to attack the argument, and resorts to ad hominem to try to win favor with the audience.

Example: We see ad hominem frequently in political campaigns. One candidate might say “My opponent is a godless liberal and can’t be trusted because she lacks moral structure.” It’s easy to see how this is an attack on the opponents personal character, rather than on her policies.

Appeal to Authority

Appeal to authority refers to the act of blindly following advice or accepting the argument of an entity based on that entity’s position of authority. For example, people often follow the advice of their doctor without researching their situation at all. In this case, the patient is appealing to the authority of the doctor, rather than asking for proof or evidence to support the doctor’s advice.

Appeal to Tradition

Appeal to tradition occurs when a person or group of people use the following thought process; “it’s always been done this way.” Well, just because something has always been done a certain way doesn’t make it the best course of action. It should be said that just because something is new doesn’t make it the best course of action either. We see the appeal to tradition fallacy in religious cultures where thousands-of-years-old scriptures dictate the earth is still flat.

Self-fulfilling Prophecy

A self-fulfilling prophecy appears when we have an outcome in mind and so we act as if the outcome were already true, which leads us to the outcome. For example, if a child believes they don’t do well with school work, they may act as if they’re no good and end up performing poorly in school. Self-fulfilling prophecies can be initiated by thoughts we have about ourselves or by the opinions of others thrust upon us.

Confirmation Bias

Confirmation bias is related to the self-fulfilling prophecy in that the result of our outcome is in mind before an experiment is conducted. The experimenter then favors evidence which shows the desired result or outcome and ignores evidence against it. This happens far too often in medical literature and is one of the main reasons that reading research thoroughly is so important.

Logical Fallacies in the Weight Loss Industry