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Dudley Dowell
Sat, Jun 20, 2015 - 03:00 PM

Why do so many people follow fad diets?

1 Answer



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Bo Bennett, PhD
Host, Doctor of Social Psychology


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Bo Bennett, PhD

Host, Doctor of Social Psychology


About Bo Bennett, PhD

I am the host of this show :) For my complete bio, please see
PrintSat, Jun 20, 2015 - 03:00 PM
According to a 2014 Marketdata report, the weight-loss market in the United States was about $60 billion, with an estimated annual revenue of about $20 billion. To put this in perspective, that is about $63 per US citizen (infants included) spent each year on products and services that offer hope to those looking to lose weight. It's a huge market built on a complicate science that few people really understand—a breeding ground for pseudoscientific fads.

A "fad" is defined as an intense and widely shared enthusiasm for something, especially one that is short-lived and without basis in the object's qualities; a craze. Fads only become fads in retrospect. When diet fads are new, they are marketed as, and believed by their followers to be a "revolution" in health science. One could argue that the first and last health science revolution was the introduction of the calorie back in the early 17th century (Hargrove, 2006). Since then, our understanding of diet and nutrition has increased incrementally and modestly with the golden rule of dieting remaining strong: burn more calories than you take in. If we are wise enough to take a lesson from history, we can look back on the fad diets of past and see how support for these diets have waxed and waned, many of which only exist today as the remnants of "foolish and anti-scientific" previous generations, when in reality, as far as scientific support is concerned, they were on the same level as the popular diets today. If we can understand why we are so drawn to the fads, then we can have more control over our reason and not let our emotions guide our health behaviors.

Here are 7 reasons why we find diet fads irresistible.

They work—for the short term. Losing weight is not difficult; it's keeping the weight off that is the challenge. Any diet that lowers your overall calorie intake will lead to weight loss. This short term success provides layman's "evidence" that the diet works, and leads to more buzz and excitement about the diet. One can avoid breathing in dangerous fumes by holding one's breath, but this is only a short-term solution that eventually fails due to strong physiological needs. While you can probably maintain a very restrictive diet for longer than you can hold your breath, the more restrictive the diet, the less likely it is to be a long-term strategy for reaching and maintaining a healthy weight.

People like to hear what they want to hear, not what they need to hear. People want to hear that their weight problem is due to the big bad food industry poisoning us all with "toxins," some demonic ingredient commonly found in foods, failure to eat the right combinations of foods, not eating enough delicious red meat and bacon, not eating according to their blood type, or many other problems that offer an easy solution or shift the blame away from the individual. What people need to hear is that they are taking in too many calories for their level of activity. This means cutting back on calories or becoming more physically active.

People have a poor understanding of complex causality. Establishing causality in science is extremely difficult and can only be done under the most strict experimental conditions, and even then causality claims are probability-based. The problem is, people make many erroneous causal attributions based on a simplistic understanding of causality. If a person on a fad diet loses weight in the first week of the diet, he might attribute the weight loss to the veracity of the claims made by the proponents of the diet (e.g., he ate the right foods for his blood type) where the loss of weight is almost certainly due to simply taking in fewer calories or exercising more. This is why all weight-loss supplements work great when combined with "diet and exercise". We should be asking, what clinical trials have been done that show support for the claims of the diet? And more importantly, what clinical trials have been done that do not support the claims of the diet? Research the claims using a neutral source (like

People have a poor understanding of science. Tim Crowe, Associate Professor in Nutrition in the School of Exercise and Nutrition Sciences at Deakin University in Melbourne, Australia, recently wrote an article beautifully illustrating how simple it is to irrationally demonize virtually any food, food group, nutrient, or chemical by drawing unscientific and irrational conclusions from actual scientific facts. Crowe (satirically) writes, "Broccoli is loaded with formaldehyde, a natural by-product of oxidation and which is known to cause cancer in rats. Formaldehyde is used in the manufacturing of plastics, foam insulation, fungicides, mirrors, insecticides, petroleum, resins and industrial chemicals. No one in their right mind would eat any of these things so when you see this list, just add broccoli to it as well." If you don't understand the basics of science (e.g., how the toxicity of something depends on the amount, not on the mere presence of it; how the convergence of evidence of all published studies is more important than a few cherry-picked studies; how the presence of an ingredient in non-edible item does not make that ingredient non-edible; etc.), then it is easy to buy into the irrational conclusions made by those trying to sell you the diet.

We want simple solutions to complex problems. The majority of people experience adverse effects by eating some kinds of foods. Figuring out what the actual causes are of the adverse reaction can be a long and frustrating process, even when done under the guidance of a certified nutritionist or a licensed medical professional. Worse, our body changes over time as do the adverse effects we experience, making solutions that are found temporary or just partial. Fad diets often offer up simplistic solutions to a myriad of health problems, including obesity, that are claimed to benefit most people or even "everybody."

The appeal to authority. We tend to take an intellectual shortcut when it comes to evaluating scientific claims by blindly trusting people in positions of authority rather than testing their claims against the body of available scientific evidence. While this heuristic might be harmless when the claims being made are in line with traditional scientific thinking, radical new ideas proposed warrant going beyond the claims of a single or even handful of experts. Remember that roughly 50% of all doctors graduated at the bottom of their class, and even some of the brightest doctors violate the Hippocratic Oath they have taken in the interest of power, fame, and/or money.

The placebo effect. Virtually all fad diets claim that their diet will make you feel better by suggesting generic feeling-based improvements such as "more energy," easily enhanced by the mere belief in the diet's claims and the excitement about the program. The initial and temporary weight loss one is likely to experience further enhances this effect.

Once we are drawn into the fad, it becomes very difficult to get out. The initial excitement converts us into evangelists for the fad (i.e., those really annoying people who won't shut up about the idea they are pushing, trying to get others to be part of it). Once we start this evangelical path, we essentially "double down" on the diet and become a victim to the sunk cost fallacy. We are no longer just defending the fad; we are defending our own judgment, and in some cases, our reputation. Eventually, our rotund figure returns, and at the very least, we end up admitting that the diet doesn't work for everybody. But not to worry—there's this new diet out...

Perhaps the best way to resist a fad diet is to realize that the reason you are being drawn to it has nothing to do with the effectiveness of the diet. Fad diets only remain alluring when the fruits of the diet is something desired rather than something already possessed. If you want to lose weight, follow the advice given for over a hundred years: burn more calories than you take in. It's not rocket science, but it is science.

Hargrove, J. L. (2006). History of the Calorie in Nutrition. The Journal of Nutrition, 136(12), 2957–2961.

Bo Bennett, PhD
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Podcast Episode: Seven Reasons Why We Find Fad Diets Irresistible

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