The 5 Biggest Myths in Nutrition: Debunking Common Misconceptions

Nutrition is a field plagued by misinformation, fad diets, and outdated beliefs. Despite advances in nutritional science, myths persist, often driven by anecdotal evidence, marketing campaigns, or a misunderstanding of complex biological processes. These myths can lead to suboptimal food choices, unnecessary dietary restrictions, and general confusion.

Here, I tackle five of the most pervasive nutrition myths, separating fact from fiction. These myths are necessary to debunk because of the effect they can have on your wellbeing:

Myth 1: Carbs make you fat

Myth 2: High protein diets damage your kidneys

Myth 3: Dietary fat is bad for you

Myth 4: You must fast to lose fat

Myth 5: Detox cleanses make you healthier

Ready to go? Let’s jump in.

Myth 1: Carbs make you fat

The belief that carbohydrates are inherently fattening is one of the most widespread misconceptions in nutrition. This myth gained traction during the low-carb diet craze of the early 2000s, driven by books such as The Atkins Diet and, later, the ketogenic diet trend. Today, hating on carbs and insulin still remains popular.

The belief goes something like this: it’s not just the calories in carbohydrates that are the problem but also the inherent fattening effect it has via insulin. The theory goes that increasing insulin via carbs blunts the use of fatty acids for fuel. Therefore, by dropping carbs, you drop insulin and gain an advantage in fat loss.  

However, high-quality peer-reviewed research does not currently support this theory. For example, a metabolic ward study (think: tightly controlled) examined whether going keto had a “metabolic advantage” over a higher-carb diet matched for calories and found no fat-loss advantage in overweight subjects (Hall, Chen et al. 2016).

In other words, when you match calories like-for-like, an overall caloric deficit matters more than dropping nearly all carbohydrates. Weight loss and gain are primarily influenced by total energy balance, not insulin spikes (Hall 2008). 

This is not the only study that found that calorie intake matters more than carbohydrate intake when the goal is fat loss. A meta-analysis of randomised controlled trials (at the top of the evidence-based hierarchy) comparing low-carb to low-fat diets found the same outcome (Bueno, de Melo et al. 2013).

. The takeaway is that there is no metabolic advantage in eliminating carbs to improve body composition. Complex carbohydrates like beans, legumes and pulses are also excellent sources of dietary fibre and nutrients, helping to support overall gut health (Oniszczuk, Oniszczuk et al. 2021).

Please note that this does not mean eating low carb is “wrong”. If getting more of your daily calorie intake from protein, fibre, and healthy fats helps you to control calories and appetite, that’s great. Focus on a calorie deficit first and reverse-engineer your diet from there.

Established bodies like the International Society of Sports Nutrition recommend a few valuable takeaways when improving body composition: find the diet that works for you, enables a sustained caloric deficit, helps you exercise frequently, and maintains lean muscle mass (Aragon, Schoenfeld et al. 2017). These are valuable criteria to think about in your life if you want to become leaner.

Myth 2: High protein diets damage your kidneys

Carbs are not the only macronutrients that are criticised. Protein can also get a bad rap. A common myth is that high-protein diets damage kidneys. Where does this myth come from, and what is the evidence for it?

The idea began in the 1980s when research suggested that high-protein diets increased glomerular filtration rate (GFR), a marker for kidney waste filtration (von Herrath, Saupe et al. 1988).

However, modern research contradicts the hypothesis that high-protein diets inherently damage the kidneys. A 2018 meta-analysis assessed 28 studies and nearly 1400 participants and showed that whilst GFR can go up with a higher protein diet, this is a normal process and does not lead to the pathophysiology or issues of the kidney (Devries, Sithamparapillai et al. 2018).

So, what is an ideal level of daily protein? The answer (like many things in nutrition) is that it depends. How much protein you eat daily depends on your goals, activity levels and preferences. Whilst the recommended daily allowance is 0.8g per kg of body weight per day, modern research suggests a higher starting point for health and longevity: 1.2-1.6g per kg of body weight (Phillips, Chevalier et al. 2016).

If you are an athlete training hard in a calorie deficit, that range can shift upwards, with research pointing towards 1.6-2.4g per kilo of body weight (Hector and Phillips 2018). To put these numbers into context, if you weigh 90kg and want to get leaner, the RDA is 72 grams of protein per day. However, the recommended amount is anywhere from 144 to 216 grams daily.

Myth 3: Dietary fat is bad for you.

A third myth that still impacts food choices for many is that eating fat is bad for you. This belief is perhaps borne out of the 1960s dietary shift when we were told to avoid fat to lose fat. One study, in particular, is commonly cited in driving the push against eating dietary fats (McGandy, Hegsted et al. 1967). Sadly, many years later, it was revealed that this study was sponsored by a group now known as the Sugar Association.

So, what’s the deal?

Current research points to vital new insights which are mind-blowing to many: saturated fat is not the only driver of increased LDL cholesterol, lowering LDL does not always improve health outcomes, certain dietary fats (such as omega-3 fatty acids) are vital for human health, and removing saturated fat does not always reduce the risk of heart disease because it depends on what you eat in its place (Tall and Yvan-Charvet 2015, Tall, Thomas et al. 2022, Yu, Qi et al. 2022, Kip, Diamond et al. 2024, Lane, Gamage et al. 2024).

For example, one recent review looked at ultra-processed food and found the following: “Overall, direct associations were found between exposure to ultra-processed foods and 32 (71%) health parameters spanning mortality, cancer, and mental, respiratory, cardiovascular, gastrointestinal, and metabolic health outcomes.” (Lane, Gamage et al. 2024). In other words, understanding the risks brought by our overall diet is more important than one element, like dietary fat.

Another systematic review compared saturated fat to trans-fat (the artificial fats found in processed foods) and concluded the following: “Saturated fats are not associated with all-cause mortality, CVD, CHD, ischemic stroke, or type 2 diabetes, but the evidence is heterogeneous with methodological limitations. Trans fats are associated with all-cause mortality, total CHD, and CHD mortality.” (de Souza, Mente et al. 2015).

This nuance matters. It shows that blanket statements about “dietary fats” are unhelpful. The first and most crucial step to improving health outcomes is to shift towards a whole-food diet that reduces exposure to processed foods and artificial trans fats.

Myth 4: You must fast to lose fat

In recent years, it has become popular for social media influencers to promote intermittent fasting as the best way to lose weight. Intermittent fasting involves cycling between periods of eating and fasting, with various approaches catering to different preferences and goals.

There are many types of intermittent fasting, including the 16:8 Method (fasting for 16 hours and eating during an 8-hour window), Alternate-Day Fasting (ADF), the 5:2 Diet (eating normally for five days of the week and significantly restricting calories (approximately 500-600 calories) on two non-consecutive days), OMAD (One Meal a Day), and more.

While fasting can be an effective tool for some and an easy way to approach fat loss mentally, it is not a universal requirement. The fundamental principle of fat loss is achieving a caloric deficit—burning more energy than you consume (Hall 2008). This can be accomplished through various dietary approaches, not just fasting (Aragon, Schoenfeld et al. 2017).

Moreover, fasting is not suitable for everyone. It may lead to overeating during eating periods, reduced energy levels, or impaired performance in physical or cognitive tasks, particularly in individuals who train hard and have high energy demands (Kerksick, Arent et al. 2017).

There is also the hormonal component to consider. Fasting has been shown to increase the stress hormone cortisol and reduce restorative parasympathetic activity (Mazurak, Gunther et al. 2013, Kim, Joo et al. 2021). In other words, intermittent fasting can be a stressor for some individuals' systems. This matters because if you are already stressed, busy, and depleted, intermittent fasting might help you lose fat in the short term but compromise your underlying health in the longer term.

Myth 5: Detox cleanses make you healthier

Detox cleanses often promise quick weight loss and work on the assumption that you need to remove toxins if you are going to lose body fat. Many books have been published offering you a 7-day, 10-day or 21-day reset, and they can often involve you living only on juices for the duration.

Let’s create a steel-man argument for detox cleanses rather than dismiss them entirely out of hand. We are exposed to countless toxicants in our air, water and food. For example, air particulates increase oxidative stress in our bodies (Jiřík, Machaczka et al. 2024). In the US, more than 10,000 chemicals are approved for use in food. Exposure to mould from food can also have adverse health outcomes (Harding, Pytte et al. 2020). So, our overall toxic burden can be high, depending upon where and how we live.

The problem with detox cleanses is the approach they take. You are often put on such a deeply restricted diet that you can inadvertently compromise detoxification rather than help it.

Detoxification in the body primarily occurs through two key phases in the liver, which processes toxins into forms that can be safely eliminated. Each phase has distinct roles and nutrient requirements (Cline 2015).

Phase 1: Activation (Biotransformation)

This phase involves converting toxins (lipid-soluble substances) into more reactive, water-soluble intermediates using enzymes from the cytochrome P450 family. Many nutrients are needed here, such as vitamins B2, B3, B6, B9, B12, Vitamin C, Vitamin E, flavonoids, glutathione, and Zinc, Magnesium, Selenium, and Copper.

Phase 2: Conjugation

In this phase, reactive intermediates are bound to specific molecules to neutralise their toxicity and make them water-soluble for excretion via bile or urine. We need a ton of nutrients here, too, including many amino acids such as Cysteine, Methionine, Glycine, Taurine, Glutamine, sulphur-rich foods such as garlic, onions and cruciferous vegetables), Choline and Betaine are used for methylation, and magnesium is used for enzymatic reactions.

In other words, to support these processes, we need a nutrient-rich, whole-food diet sufficient in protein. Healthy detoxification is best achieved by supporting cells and systems with a nutrient-dense, balanced diet, hydration, and regular physical activity to sweat out toxicants (Panda, Komarnytsky et al. 2023).

Conclusion

Nutrition myths can send our health sideways, even when we are trying our best to do the right thing. In this post, you learned that carbs do not inherently make you fat, a high-protein diet is not dangerous for your kidneys, the right dietary fats are not bad for you, intermittent fasting is not required for fat loss, and detox diets can be disastrous for your health when lacking in particular nutrients. By focusing on evidence-based practices, embracing a balanced diet, and tailoring your nutrition to your needs, you can achieve sustainable health and wellbeing without falling prey to myths and misconceptions.