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Three Nutrition Myths Debunked

To round out the year, let’s finish with something fun: debunking three pesky nutrition myths that just will not die.


Nutrition myths: we love to hate them. On the one hand, it’s quite satisfying to debunk them. On the other hand, they can cause serious harm to people, which is upsetting, and makes it all the more important to tackle them head on. In this article, we address three common myths and explain why they're misleading. Let’s dig in!

Fake news, misinformation.

#1 ‘Carbs Make You Fat’

Needless to say, carbohydrates are not inherently fattening. In fact, multiple large-scale studies have reported similar reductions in weight for those eating weight loss diets either lower or higher in carbohydrates (1,2), and at least in the very short-term, high-carbohydrate diets may lead to more fat loss than low-carbohydrate diets when calories are reduced (3).

While it’s true that certain high-carbohydrate foods like sugar-sweetened beverages (e.g., Coke) are strongly associated with weight gain (4), not all carbohydrate-rich foods are fattening. In fact, people who eat diets richer in healthy carbohydrate-rich foods like fruits, vegetables, whole grains, and legumes have lower levels of body weight (5,6). Now, this doesn’t mean that it is the carbohydrates within these foods that leads to a lower body weight, but it clearly shows that if carbohydrates are fattening, they’re not doing a great job!

Muesli, healthy breakfast, carbohydrates.

Muesli: an example of a healthy carbohydrate-rich breakfast.

#2 ‘Coffee is Dehydrating’

Despite the fact that caffeine—one of the main substances in coffee—is a diuretic—or a substance that makes us pee—evidence shows that coffee is not dehydrating (7). I know, it seems unbelievable, right? But when you consider that coffee grounds are only 1–2% caffeine (7), and thus the vast majority of a brewed cup of coffee is water, it’s not super surprising. This myth highlights the importance of scrutinising a claim, despite its apparently rational underpinning. If you want to dive a little deeper on this topic, see our previous article all about it.

#3 ‘Ultra-Processed Foods Are Inherently Unhealthy’

While ultra-processed foods as an entire food group are associated with poor health outcomes, this doesn’t mean that all ultra-processed foods are necessarily unhealthy. Because the definition states that any food containing an ‘unnatural’ ingredient is an ultra-processed food (8), this can lead to healthy foods (e.g., calcium-set tofu, commercial wholemeal bread) considered within this overall group of foods that are often not so healthy (e.g., cakes, doughnuts). As an analogy, this would be akin to stating water is unhealthy because it is an ingredient in Coke! If you would like to learn more about this, we have covered this topic in detail in a previous article.

Are processed foods healthy?

Check out our previous article on processed foods.


I hope you enjoyed this article and learned something from it. Thank you to our regular readers for reading along each week here at the Training121 Blog. This is our last article of the year, so I want to extend my well wishes to you all over the Christmas period—enjoy it! We all need a break.

Merry Christmas! We look forward to providing you with more science-based content in 2024.

Patrick Elliott, BSc, MPH

Health and Nutrition Science Communication Officer at Training121

Twitter/X: @PatrickElliott0


(1) Gardner CD, Trepanowski JF, Del Gobbo LC, et al. Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion: The DIETFITS Randomized Clinical Trial. JAMA. 2018;319(7):667–79. Available at:

(2) Höchsmann C, Yang S, Ordovás JM, et al. The Personalized Nutrition Study (POINTS): evaluation of a genetically informed weight loss approach, a Randomized Clinical Trial. Nat Commun. 2023;14(1):6321. Available at:

(3) Hall KD, Bemis T, Brychta R, et al. Calorie for Calorie, Dietary Fat Restriction Results in More Body Fat Loss than Carbohydrate Restriction in People with Obesity. Cell Metab. 2015;22(3):427–36. Available at:

(4) Malik VS, Hu FB. The role of sugar-sweetened beverages in the global epidemics of obesity and chronic diseases. Nat Rev Endocrinol. 2022 Apr;18(4):205–18. Available at:

(5) Termannsen AD, Clemmensen KKB, Thomsen JM, Nørgaard O, Díaz LJ, Torekov SS, Quist JS, Faerch K. Effects of vegan diets on cardiometabolic health: A systematic review and meta-analysis of randomized controlled trials. Obes Rev. 2022 Sep;23(9):e13462. Available at:

(6) Jarvis SE, Nguyen M, Malik VS. Association between adherence to plant-based dietary patterns and obesity risk: a systematic review of prospective cohort studies. Appl Physiol Nutr Metab. 2022 Dec 1;47(12):1115–33. Available at:

(7) Lowery LM, Anderson DE, Scanlon KF, et al. International society of sports nutrition position stand: coffee and sports performance. J Int Soc Sports Nutr. 2023;20(1):2237952. Available at:

(8) Monteiro CA, Cannon G, Levy RB, et al. Ultra-processed foods: what they are and how to identify them. Public Health Nutr. 2019;22(5):936–41. Available at:

Technical Terms

Caffeine: A substance found in coffee that is a central nervous system stimulant, meaning that it improves attention and cognitive performance, and also improves a range of exercise performance outcomes.

Diuretic: Any substance that promotes the increased production of urine (diuresis).

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