Skip to main content

I’ve said it before but it bears repeating – the internet is both the saviour and the thorn in the foot of the fitness industry. On one had it cannot be denied that trainees now have access to more information about nutrition, advice about programming and even virtual coaching (which I wholly recommend, by the way) than the iron brethren of old could even dream about.

Just think about it – what if rugby players, boxers and even Olympians of the 50’s and 60’s knew what the average 17 year old gym-goer of today knows about nutrition?

(This is actually a fun discussion to have – COULD the greats have been greater? I’ll leave that one there for now).

But there’s a flip-side. The internet is packed with gurus, profiteers and even worse – followers of these figures who will defend their idol’s position at all costs in the face of any evidence you are able to provide which goes against their zealous beliefs. These people have an emotional (or monetary, or other) investment in the information they ‘know’ and this means that changing their mind is like trying to change the direction of the wind. For example, if someone has routinely eaten chicken breast and asparagus 8 times per day in order to get lean and you tell them that they can diet in a much easier fashion, they are unlikely to want to hear that they have been suffering so much unnecessarily. Any discussions these individuals are involved in tend to go down the road of what is known as ‘logical fallacies’.

A logical fallacy is a flaw in the human thought process which is not apparent to the person that makes it. We like to think ourselves rational beings and we often assume that the way in which we think is flawless and infallible but – well – we aren’t (bear in mind that over 90% of drivers think they are ‘above average’ at driving and you’ll understand just how much of an inflated ego just about everyone in the world has, myself included). No, we are prone to lapses in the way our mind works, and being able to identify these lapses – both in yourself and in someone you are debating with or listening to the advice of – is one of the most fundamental things required for the development of critical thinking skills. Spotting logical fallacies or ‘bad arguments’ will help you to identify situations where you are potentially being given incomplete or straight up wrong information and THAT is very important given the amount of crap you can read about fitness, nutrition, health and ANYTHING on the internet.

Remember, to understand a subject fully one must truly understand one’s own view but also wholly understand the opposing view, and the same goes for debating logically. To be good at it, you need to know how to do it wrong.

Critical thinking is, in my opinion, the single most important skill you can learn in order to progress in your self-education. Disseminating information into 'useful' and 'bogus' is an art form that many people take years to master. I won’t profess to be all knowing in this field, honestly I don’t know anyone who can, but I’d like to think I can help you smell bullshit even when it’s been covered in roses.

Below I’ll list the most common logical fallacies you are likely to encounter alongside some very popular examples. For each I’ll explain why the information is incorrect and then explain why the arguer has come to this conclusion so you are able to identify similar mistakes in others.

I’ll start with the big one…

A Straw Man Argument

This is probably the most common logical fallacy you will encounter in the realm of nutrition as it lends itself quite well to the field. The basic premise here is that someone is unable to disprove a position (knock down the ‘man’) so they will construct something else which is similar (the ‘straw man’) and disprove (knock down) that instead.

A prime example here is when a person states that Flexible dieting is a poor approach to nutrition because although you can improve body composition with suboptimal foods, the focus should also be on health. This statement is true, but the claimant has not actually argued against flexible dieting, they have argued against something which they made up and appears similar – a dieting practice which does not take health into account.

Flexible dieting proponents do, indeed, recommend a large intake of whole foods and advise a great range of micronutrients which will result in improvement in health markers. They advise against consuming foods which make someone react poorly (either physically or psychologically) and they understand that varying degrees of flexibility are appropriate for different people and the same person at different times. The focus IS always on health – but by representing flexible dieting in a different and far more negative light than what is actually true a person who disagrees with the practice is able to convince others to do the same.

If someone makes a claim which represents something very negatively, it’s always important to ensure that what the person has said is actually true before you agree with them. You may be shocked at how rare this will be…

An Appeal to (Irrelevant) Authority

This is the practice of making or defending a claim because someone you respect said it was so.*

*This one needs some clarification before I go on. An appeal to authority is not ALWAYS a logical fallacy – Academics and scholars will often cite things which have been claimed by respected experts in a field and this is fine. If someone states that their university lecturer who holds a PhD in human biomechanics stated that women have a larger Q angle than men, that is a perfectly good argument – the issue here is when someone cites an ‘authority’ who isn’t an expert.

I’ll give two examples here. Firstly the most common one is when someone makes a claim based upon information handed down by someone who has had success doing something themselves such as a pro bodybuilder.

"Don’t eat carbs at breakfast because Ben Pakulski says…" was probably the most prominent one at the time of writing so I’ll dissect that one. Now, as I’ve explained in a few other articles over the years which you’ll find dotted around the internet, the timing of your carbohydrates matters very little from a physiological standpoint, but because Ben has positioned himself as an expert and because he is - well - somewhat well developed, people will take his word as gospel. Unfortunately when you look at his credentials, B-Pak is no expert in nutrition and the claims he makes are largely made with a deeply rooted financial bias towards selling his programs and coaching services, so debating subjects based upon what he said amounts to a logical fallacy. Whilst what B-Pak says has obviously ‘worked for him’ this does not make it true (this ties into another fallacy, but I’ll move on to that in a moment).

A second example of the appeal to false authority is when people who are fans of Dr. Oz, Gary Taubes, Dave Asprey, the Food Babe or other industry figures back up their claims with the work of these people. While each is very intelligent and each backs what they say with what looks on the surface like legitimate science and reasoning, they are not experts and therefore the things they claim have no actual weight when it comes to debating (much like nothing *I* say actually matters when debating).

Evidence needs to come from either published data or the interpretations thereof of a respected and well-educated expert in that SPECIFIC field. An irrelevant authority CAN make legitimate claims – Dr. Spencer Nadolsky is an osteopath but is very well-read when it comes to nutrition and supplementation, so is in fact someone who’s word holds weight - but as always, regardless of who says something it is imperative that you look back at the primary evidence before accepting that something which has been said is true.

A False Dichotomy

The false dichotomy (sometimes known as a false dilemma) is the mistake of thinking that things fall into either one camp or another and there is no middle ground. The common example in our industry is the idea that HIIT and LISS cardio are mutually exclusive and one must be good whilst the other is bad. The truth is that both have their applications and depending on context both could be applied to almost any individual.

Another example is the ‘low carbs vs. low fat’ (or high carbs/fat) argument of nutrition which often presents itself thusly: "if I eat a huge bowl of pasta I feel really sluggish therefore I am going to go on a low carb diet". Clearly the person doesn’t do well with a very high carb intake, but this does not necessarily mean that a moderate, midline approach would be unsuitable.

Mistaking correlation for causation

Ah, the darling of the media industry and the pain in the ass of every fitness professional with a slight understanding of the scientific method. The examples for this are almost innumerable as they have been selling newspapers for decades, but I’ll start by using a slightly more interesting one to illustrate my point.

The book ‘The China Study’ is a very popular read and is often cited by proponents of a low fat/protein and high carb plant based diet. In it, the authors spend a great deal of time creating and defending the position that animal matter is the scourge of the modern diet and that be eliminating meat, fish, dairy and eggs one can reduce or even eliminate one’s risk of chronic illnesses such as coronary heart disease, diabetes, and cancers of the breast, prostate and bowel. They even conclude at one point that "Eating foods that contain cholesterol over 0mg is unhealthy".

Their reasoning for this?

The information in the book is based upon a project known in some circles as the ‘Grand Prix of Epidemiology’ – The China-Cornell-Oxford Project which was a comprehensive study of dietary and lifestyle factors which are considered possibly related to disease mortality rates in China.

Researchers chose two villages from each of the rural counties in china (so 130 villages total) and then selected 50 families from each (meaning 6500 families). They examined the dietary habits and blood markers of one adult male and one adult female from each family in order to estimate what the typical scores were for each village. They then took the death rates in each county over a 2 year period which could be related to various diseases and compared the two sets of data.

This was repeated 10 years later in order to spot patterns.

They concluded that over the 10 year period blood cholesterol rose at around the same rate as ‘western disease’ rates did. They noted that those who experienced the worst increases were those who consumed the most animal flesh, and therefore concluded that "the lower the percentage of animal-based foods that are consumed, the greater the health benefits – even when the percentage decreases from 10%-0% calories".

However, there’s a fly in the ointment.

This was not a causal study, it was an epidemiological study. Epidemiology seeks only to spot correlations between things and it is a mistake to assume that two things happening together are actually linked.

For example, did you know that the number of ice creams which sell during any given year is VERY closely correlated to the amount of people who will be murdered during that year? These two things cannot possibly be related, but the numbers are uncannily similar.

Another more relevant example is when someone claims that they have started to introduce BCAA to their intra-workout drink and now they feel that they recover better - therefore BCAA help recovery. The two things happened at the same time but it’s vital that we look at other factors:

  • BCAA have calories. Has the person simply increased their calorie intake? Or has their protein intake now become adequate?
  • The person has been training for the entire time. As you train, your body becomes more efficient at recovery on its own due to the repeated bound effect – would the reduced soreness have happened without the supplement?
  • The person started taking BCAA in order to reduce soreness – have they been experiencing the placebo effect?

Unless a mechanism is demonstrated, it’s very difficult to draw conclusions from correlation (though correlation can often hold clues to possible causation, so don’t discount it entirely unless you are aware of mechanisms such as the above regarding BCAA that explain the phenomenon better).

Similar to the above, the actions of professional bodybuilders are often considered to be a good idea for other gym goers as it ‘worked for them’. Likewise it’s common to hear someone advising someone else to do something a certain way because they did it that way themselves and it ‘worked’. This is fallacious as it potentially falsely assumes that what was done by the claimant directly caused the outcome, when it’s perfectly possible that what happened, happened alongside the actions of the claimant by chance or indeed in spite of what they did.

One other example is the recent newspaper story stating that red meat gives you cancer, because a study showed that those who consumed red meat were more likely to get cancer. This is easily explained when you consider that often those who consume red meat are consuming it as burgers, ribs, kebabs and pepperoni pizzas to compliment a sedentary lifestyle which also involves smoking and alcohol. Those who DON’T consume red meat tend to be somewhat more health conscious – exercising and consuming more vegetables and fibre.

A final example would be that those who skip breakfast tend to be more overweight. This doesn’t necessarily mean that skipping breakfast makes you fat, rather breakfast skippers are often those with high stress lifestyles (meaning they rush in the morning) or altogether blasé approaches to their nutrition.

A false slippery slope

This is the assumption that one event will inevitably end up in a resultant event or sequence of events which are unpleasant or undesirable.

You will often see it, again, in arguments over Flexible Dieting whereby proponents of FD make the claim that ‘clean eating’ will inevitably lead people to episodes of binging when this simply is not the case. Yes, some folks who adopt a restrictive diet have enormous ‘cheat meals’ or simply eat their weight in ice cream occasionally when they can’t take it any more – but an equal if not larger proportion of those who adopt a ‘clean eating’ lifestyle genuinely enjoy what they eat and suffer no such tendencies.

On the other side of the coin there are those who make the claim that someone counting their macronutrients in order to eat flexibly is a behaviour which will result in disordered eating practices and a fear of ‘unknown’ foods which they cannot track.

Both arguments are false and those who use them tend to do so deliberately to make a point or sell something. I would personally be very cautious when you see either one crop up.

Bold Generalisations

This one is a little trickier to spot, but it’s pretty important. In essence what we are looking at here is when a person extrapolates information about a very select or specific group to make recommendations or claims to a larger and potentially unrelated population. I say it’s tricky to spot because it’s not always apparent – you may need to check someone’s sources.

Let’s look at the claim that ‘’Sugar is making us fat’’. This can be defended by offering a study in which rats fed a high sugar diet gained more weight than rats fed another diet. This cannot be extrapolated to humans as the pathway which allows carbohydrates to be converted into fat (de novo lipogenesis) is incredibly efficient in rats but not in humans. It’s also worthy of note that sugar consumption hasn’t actually gone up all that much as a percentage of total calories, rather we are eating more of EVERYTHING in recent years - so the generalisation is flawed and there is something else going on to cause the obesity crisis.

Another would be to make the claim that consuming gluten is terribly bad for you. For those with Celiac disease gluten consumption can be life threatening, and although there is a lot of debate about the legitimacy of it, non celiac gluten sensitivity is a subject which is gaining much more exposure. This DOES NOT, however, mean that gluten should be avoided by everyone any more than the fact that nut allergies are common means that I shouldn’t eat PB from the jar (the fact I haven’t seen my abs in years is what says that…).

Gluten is perfectly fine for consumption in anyone who doesn’t have specific symptoms which are exacerbated by it and generalising recommendations for what is a very small minority is a big mistake to make.

Appeal to tradition

I do it like that because that’s how it’s always been done.

In the modern world of physique competition it’s pretty well known that performing high rep training with low loads and eating almost no food whilst doing a TON of cardio, then peaking for a show by manipulating sodium and then drinking alcohol to ‘dry out’ is a bad idea...yet a lot of folks still do it.

Explain why this is a bad idea and you will get the above argument, which is a logical fallacy. It is wrong to assume that the way things have always been done is the best way to do something, and this counts EVEN IF THE OLD SYSTEM WORKED.

Take, for example, the idea that eating 6 meals per day is needed to get lean – we now know that it isn’t but people managed to get lean by using the method. It worked, but that didn’t make it right.

This is also used often in alternative medicine. Reflexology is an ancient Chinese practice involving massaging specific areas of the feet in order to heal corresponding areas of the body. The old explanation for this was that it helped to channel Qi (sometimes spelled chi) which is your body’s energy field. A slightly more updated version is that nerves running around various areas in the body are also found in the feet and manipulation from these nerves by proxy will aid in the healing process. Unfortunately all have been able to determine is that reflexology makes your feet feel better (1) and may be helpful when you’re stressed… because foot rubs are kinda nice.

Just because something has been around for a long time – it doesn’t make it right. Gay marriage has been illegal for centuries and slavery used to be quite popular… certainly not traditions I would like to see upheld.

Affirming the Consequent

OK, bear with me on this one because it’s a lot more common than a lot of folks realise but it’s a little harder to explain.

When arguing it is perfectly acceptable to make certain assumptions based upon what we know. For example if we know that every time you drink a lot of gin you get drunk, we can state with confidence that because you are drinking a lot of gin, you are going to get drunk. That’s fine.

The fallacy comes in when you reverse it, using the example above it would be false to claim that you are drunk, therefore you have definitely been drinking gin (you could have been drinking anything).

Bringing this back to fitness and nutrition I think this is a very important example: Those who are lazy, greedy and gluttonous usually end up overweight, this is true. That does NOT make it true to say that those who are overweight are always lazy, greedy and gluttonous. There is a lot more at play when it comes to obesity regarding psychological and even physical issues and THIS is why fat-shaming is such a terrible thing in my opinion. It doesn’t often help anybody and can often lead to things becoming worse for those being shamed.

Be very careful when making assumptions based upon affirming the consequent.

To be good at it, you need to know how to do it wrong

Onus Probandi

The burden of proof lies with he who makes a claim.

What this means is that a person who makes a claim must back it up with something if it is requested of them, otherwise the claim can be considered to be false and we must accept the other viewpoint. The fallacy comes in when a claimant demands someone proves him or her wrong.

In order to explain this fallacy we will consider health effects of low carb dieting for healthy individuals.

When we consider this point, there are three potential broad outcomes. The outcomes are:

  • Low carb diets are indeed universally beneficial for health
  • Low carb diets are neutral for health and the decision one makes regarding macronutrient ratio should be made based upon preference and context
  • Low carb diets are actually deleterious to health.

As you can see the three outcomes represent a spectrum with two extreme ends and a neutral middle ground. When arguing it is considered that the middle ground is the default position and the two extreme ends as just that – extreme. The truth lies somewhere on the spectrum and any debating exists to find exactly where it does lie.

This is where we need to consider the burden of proof.

If I make the claim that low carb dieting is healthy I am adopting a position which is away from the neutral middle ground and I must therefore be prepared to give evidence to back my claim. I CANNOT make the claim that low carb dieting is healthy and then when contested ask someone to prove me wrong.

This fallacy occurs a lot when alternative medicine is brought up. The claim is that a certain supplement or procedure (which usually comes at a high price) can heal people. This is an extreme end of the spectrum and the burden of proof therefore lay with the claimant. Unfortunately the claimant is unable to provide evidence so will, typically, state that those they are debating with cannot prove it doesn’t work.

That’s not how it works, sorry.

Ad Hominem Attack

Finally we have the ad hominem, translating as ‘to the person’. This is a fallacy which involves an individual discrediting an argument based upon an unrelated characteristic of the claimant. It’s often seen on internet forums whereby the views of someone are discredited because they typically have inferior physiques or sporting achievements to those whom they are arguing against.

A frequent victim of this is Dr Brad. Schoenfeld who is probably the leading expert in the world on muscular hypertrophy. He has written and published countless papers and performed numerous important clinical trials and systematic reviews. Put simply – his work has been invaluable and a lot of what we know about hypertrophy in some way relates to the work of this guy.

Problem is the dude ain’t especially jacked. He’s in shape, sure, but he’s no Phil Heath.

Funnily enough, when one spends the majority of one’s time in a lab learning about hypertrophy you don’t get a great deal of time to spend on training and eating in order to cause said hypertrophy in yourself.

Similarly another true expert in the field of nutrition, Lyle McDonald is well known both for being a respected and incredibly intelligent/valuable source of information on all things nutrition and fat loss, but his online persona is awful.

I mean, truly awful.

Lyle is a full-blown internet troll who uses foul language and throws around insults when he feels like it. He will relentlessly ‘go after’ people who he disagrees with and overall acts like an ass on Facebook.

Problem is, it’s difficult to discredit him or ignore him because of it because he is pretty much always right and can always defend his position with data.

Closing thoughts

This is not an exhaustive list but I think I’ve covered the majority of what you will see online. I hope it’s been interesting if not useful, and I hope that you can use some of what you’ve read here – if not to argue yourself – to spot when someone is giving out false information and backing it with what seems at first like a credible argument but may in reality not be so well grounded.


  1. Ernst et al (2011). Reflexology: an update of a systematic review of randomised clinical trials. Maturitas.

Post last updated on