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Six reasons diets don’t work

Why diets can be harmful for triathletes and other endurance athletes

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Dieting and weight manipulation is heightened when it comes to sport. Diet culture is especially prevalent in sports where athletes have a strong desire for leanness: aesthetic sports, weight-class or weight-sensitive sports, or where a certain body weight or type is believed to improve performance. Many studies have also shown that athletes have higher variability in their weight, body dissatisfaction and prevalence of eating disorders compared to a non-athlete population.

The combination of pressure from media, peers, coaches and others to maintain a specific body type and weight for a sport, being immersed in a highly competitive culture and the appealing claims of dieting creates a perfect storm for chronic dieting and developing an unhealthy relationship with food. This can be extremely detrimental to an athlete’s short-term and long-term health and athletic career.

The diet industry is a multi-billion-dollar industry that thrives off peoples’ insecurities. Fad diets make false promises and unrealistic claims for rapid weight loss. Although some degree of weight loss is often seen in the short-term, these restrictive diets are not sustainable and can actually lead to more weight gain long-term. Within a few weeks of restricting your body of important nutrients (fats, carbohydrates or protein), your body will be in a state of mental and physical deprivation. When deprived, you will likely end up over-eating the “unhealthy” foods you tried to avoid in the first place. This is not because of a lack of willpower- it is because the diet was impossible to maintain in the first place.

It is important to note that some diets are necessary and recommended for various health conditions (For example: A ketogenic diet for epilepsy in children, Gluten Free diet for Celiac Disease, etc.).

Related: Gluten-free diets may lead to compromised performance


Six reasons why diets don’t work:  

Diets can take on many different forms. Many restrict overall calories and energy, while others also manipulate and demonize (making you feel like they are “bad”) certain macronutrients- fat, carbohydrate and protein. 

If you are currently following a diet, I want you to ask yourself these questions: Why are you following this diet? How have diets in the past made you feel? Were they sustainable?

  1. Diets can be very restrictive and rigid. Athletes tend to thrive with structure, regimented planning and an increased focus on numbers and tracking. However, too much rigidity and structure can be detrimental as our eating patterns are not designed to be perfect. It is important to stay flexible, include a wide variety of foods and move away from creating strict rules that control and limit the foods we eat.
  2. Diets tend to limit, or completely eliminate, a major food group from your diet. Every food group provides unique and important nutrients for your body. When a diet is demonizing a food group or type of food, it is a good indicator that it is a fad diet.
  3. Diets are not sustainable or realistic. Remember that 99.9 per cent of diets fail. You do not fail the diet- the diet fails you.
  4. Diets are marketed to peoples’ insecurities. Our society and sport culture are constantly reinforcing body ideals. Whether we believe we need to look a certain way in order to be accepted, perform optimally in your sport, or obtain health and happiness, diet culture is taking advantage of these insecurities and selling you false promises.
  5. The majority of diets lead to more weight gain in the long run. They also increase the risk of developing disordered eating habits over time. Diets give people false hope for losing weight quickly, easily, and permanently. When we deem certain foods as “bad” or avoid them completely, we associate them as being forbidden and put them on a pedestal. When we do find ourselves around these foods (at a social gathering, holiday or birthday celebration), they become extremely tempting and easy to over-consume.
  6. Diet culture encourages us to restrict calories, over-exercise, skip meals and ignore our hunger cues. Instead, we should be fueling our bodies, taking rest days when we need them, eating frequent balanced meals and snacks, and honouring our hunger.
photo: Getty Images

Related: The pros and cons of Vegan diets for performance and the planet

Do you follow food rules?  

Food beliefs and rules evolve are learned over time. We are not born counting calories, or thinking “I can’t eat past 8 pm,” or believing “I can’t eat bread because it makes me gain weight.” Strict rules around food become problematic when foods are completely avoided, as it can provoke feelings of guilt and shame and anxiety when these rules are broken.

Do calories determine how much you eat? Do you weigh your food? Do you only eat at certain times during the day? Do you completely avoid certain foods? Why?  

Here are some examples of food rules and beliefs: 

  • I only eat 1,500 calories a day.  
  • I can only eat half a banana because there are too many carbohydrates. 
  • I avoid any foods with added sugar. 
  • If I eat cake, then I have to go to the gym for an hour. 
  • I stop eating after 7 pm. 

I challenge you to ask yourself why you follow these rules and for what purpose? Do these cause more stress in your life?  

I want you to picture yourself heating up leftovers for the third time this week. This meal is very familiar to you, you may even be feeling like you are “sick of eating the same thing.” This is the concept of habituation. Now think about your birthday and how it is the one day of the year that you get to enjoy your favourite cake. This is exciting, and you may tend to overeat a little, but this is also part of normal eating. The more deprived, restricted and forbidden the food becomes, they greater the tendency to overconsume them.  

It is also very common to think “Once I start eating chips or cake, I can’t stop.” This indicates that you have been deprived of this food for a long time, and that there is a lack of habituation. Without habituation and unconditional permission to eat them, these foods will continue to feel “scary” and “forbidden.”  

Characteristics of Disordered Eating: 

  • Restricting many foods or eliminating food groups 
  • Anxiety or feelings of guilt associated with specific foods 
  • Strict rules and routines surrounding eating and exercise 
  • Increased preoccupation of food and weight 
  • An impaired quality of life due to a preoccupation around food, exercise, and body image 
  • Feelings of lack of control around eating 
  • Large focus on body shape or weight 
  • Weight is heavily associated with self-worth 

Notice how many of the characteristics of disordered eating are being reinforced and supported through diet culture? 

Photo: Getty Images

How can dieting negatively affect athletic performance? 

Dieting and/or restricting energy can cause many short-term and long-term physiological consequences to your body, also known as “Relative Energy Deficiency in Sport” or RED-S. When you are not consuming enough calories to support all physiological functions needed to maintain optimal health, whether unintentionally or not, you are in a state of low energy availability.  

Your body undergoes many physiological changes and adaptations as it is biologically designed to survive. These include a decrease in your metabolism, increased body fat storage, increased hunger and decreased leptin (a hormone that tells you when you’re full), an increased preoccupation with food and more. Your ability to adapt to training, glycogen storage and muscle tissue repair are also all impaired with low energy availability. 

Various long-term consequences include reproductive and growth hormone suppression, detrimental impact on bone health, increased susceptibility for developing eating disorders and disordered eating, impaired immunity, increased psychological stress, increased risk for nutrient deficiencies and much more.  

(Please don’t hesitate to contact a health professional or registered dietitian for more information or help with any disordered eating/ eating disorder related behaviours.) 

A few reminders: 

  • Your body image doesn’t change when you change your body, it changes when you change your mindset. 
  • Start rejecting the idea that weight or fat is something that you constantly need to lose. 
  • I challenge you to reframe the way you view foods that you feel guilty for eating. They can exist as part of a healthy and normal diet. 
  • Remember that diet culture sets you up for failure, it is not your fault. 

Heather Noble. RD, is a triathlete and a sports nutritionist for CL Performance Training.

This story originally appeared in the September, 2021 issue of Triathlon Magazine Canada.