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Writer's pictureAmanda Turner, RD

Fad Diets: Proceed with Caution

Updated: Sep 17

Amanda Turner, RD

There are a lot of trendy diets out there that come with the promise of quick results. They’re advertised as simple tools you can use to take control of your health, feel better and look better. Health food companies and restaurants have even started catering to these fads. We have all seen the keto friendly menu options, the grain-free tortilla chips and the paleo snack bars. We’ve all listened to colleagues and friends talk about their intermittent fasting schedules. Certainly, these extreme diets can be effective in some specific circumstances when followed correctly. But for the vast majority of the population, they simply don’t work. In fact, they can be counterproductive, even dangerous.


Let’s use the Ketogenic Diet, or as it is most commonly known, the “Keto” Diet, as an example. The premise behind this diet is essentially to mimic starvation. Glucose, (mainly produced by carbohydrates), is our body’s preferred source of energy. When there is not enough glucose available (like during starvation), most of our body tissues can use fat and protein for fuel instead. Our brain, however, has a more difficult time adapting. For our brain to continue functioning effectively, it needs an alternative energy source. So, our body starts to break down stored fat to produce chemical compounds called ketones, which our brain is able to use for fuel. This process is called ketosis. The goal of the Keto Diet is to get the body into this starvation mode (ketosis) so that it breaks down stored fat, resulting in fat reduction and weight loss. It sounds simple enough, but there are some red flags to consider. 


The diet itself is high fat, moderate protein and low carbohydrate and can be very challenging to stick to because it is so restrictive. It isn’t possible to kind of follow a keto diet because if you consume more than the recommended amount of carbohydrates, your body will switch back to using glucose as its main energy source, therefore defeating the purpose of the diet all together. Because protein can also produce some glucose, the same can be said for eating more than the allotted amount of protein. In either case, you will simply be eating a high fat, low fibre diet, which comes with common side effects of constipation, fatigue and social isolation and puts you at risk for nutritional deficiencies, disordered eating and health conditions such as heart disease and diabetes. Not to mention, it is hard to lose weight eating high fat foods when your body is no longer breaking down stored fat. It is also important to consider that, if not followed correctly, this diet can be dangerous. There is a risk that the body could produce excessive amounts of ketones, leading to a condition called ketoacidosis which can cause damage to body tissues and in extreme cases can even result in coma or death. Similarly, it can be harmful for the body to be rapidly pulled out of active ketosis. Meaning, if you have followed the diet correctly and your body is actively using ketones for fuel and then you suddenly have a “cheat day” and eat a bunch of carbohydrates, there could be serious consequences as your body tries to quickly adapt to the sudden influx of glucose. It is really an all or nothing diet. 


There is some promising evidence when it comes to using the Ketogenic Diet to manage certain conditions, such as epilepsy and, in some cases, diabetes. Epilepsy treatment was where the idea of intentionally inducing ketosis originated and where most of the research has been focused. This diet has more recently had some success with regards to rapid weight loss as well, which is the main reason it has gained so much popularity.  However, we must keep in mind that these patients are being guided, and closely monitored, by professionals. Further, speaking specifically to weight loss, the Keto Diet is meant to be used short-term as research has shown harmful effects when used long-term (such as decreased bone density and muscle loss). Which means, if used correctly (ideally under the guidance of a professional for safety purposes) for a short period of time, it can be an effective tool for kick starting lifestyle changes and weight loss. But the weight loss is challenging to sustain long term, and can result in more weight gain once the Keto Diet is no longer being followed. Intermittent fasting is another fad that is gaining some traction and is similar to the Keto Diet in that it also seeks to mimic starvation and is challenging to stick to. Therefore, in addition to its own specific red flags, some of this keto discussion can be applied to fasting as well.


All fad diets come with their own list of safety concerns, potential harmful long term consequences and sustainability issues. For instance, many of the current fad diets have a common theme of declaring war on carbohydrates; allowing for minimal carbohydrate intake. This one aspect alone can be harmful as carbohydrates come in MANY different forms, several of which provide us with important nutrients. Think about it this way: you would never group broccoli in with fast-food donuts, but that is exactly what some of these diets are doing. Broccoli and donuts are both carbohydrate sources, but they have VERY different nutritional profiles. One is packed with fibre, vitamin C and antioxidants, while the other is full of processed sugar and saturated fat. Yet, these fad diets are telling us they belong in the same category. Similarly, a bowl of steel cut oats is a source of iron and fibre, while a bowl of white pasta offers very little nutritional benefit. Again, both are carbohydrate sources and are treated the same by these diets. Before embarking on a trendy diet, it is important to consider these things. It is also highly recommended that you consult a professional; not a life coach or a health food store employee, but a qualified clinician such as a physician who specializes in nutrition and/or metabolic conditions or a registered dietitian who specializes in these extreme diets. 


Bottom line, for the majority of the population, fad diets are not the answer. Healthy eating doesn’t have to be so complicated. There are less restrictive, safer and more sustainable options. As a registered dietitian, I provide trusted, evidence-based nutrition guidance to help you meet your goals.




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