Popular Diets and Athletes – Promises, Premises, Pros and Cons!


Athletes young and old like diets that promise improved sport performance, reduced body fat, increased muscle mass and improved health. Training mates, social media, TV documentaries and the popular press are abuzz with the latest diet fads or lifestyle plan and what they can do for us as athletes. A recent review by a Professor of Nutrition from the USA examined the premise, promises, pros and cons of four popular diets currently doing the rounds – the Raw Food Diet, the Gluten-Free Diet, the Fast Diet and the Paleo Diet. Here is what she came up.

How do they Rank as Diets?

For the last four years, US News and World Report ranks the best diets from best (ranking 1) to worst (ranking 32) using a nationally recognised panel of experts and specific criteria. Table 1 below shows how the Raw Food Diet, the Fast Diet and the Paleo Diet rank in the eight categories examined.

Table 1: Ranking of the popular diets 2014 (1 = best diet; 32 = worst diet). The gluten-free diet was not ranked but information is available here.


Raw Food Diet

Fast Diet

Paleo Diet

Best overall diet




Best weight-loss diet




Best diabetes diet




Best heart-healthy diet




Best healthy eating diet




Easiest diet to follow




Best plant-based diet


Not ranked

Not ranked

Let’s take a look at the four diets in turn and see what the science says about these diest when it comes to athletes and sport performance.

  1.  Raw Food Diet. These diets are frequently vegan diets but can include raw meats, cheeses and milk. Raw foods are defined as never having been heated to greater than 115 degrees F (46 degrees C), never processed, microwaved, irradiated, genetically-modified, or treated with herbicides or pesticides. Premise: Proponents say raw foods are healthier because cooking destroys most of the vitamins and minerals and phytonutrients in foods. Cooking also destroys the enzymes in raw foods which the proponents say are important for good health. Promises: The marketers of this diet say it promotes weight loss, ‘detoxifies’ the body (what does that really mean?), prevents and reverses diabetes, and improves energy levels. Pros: The Raw Diet is rich in fruit and vegetables and thus high in vitamins and minerals. It’s also high in fibre and phytonutrients, low in sugar, salt and fat. It’s great for losing weight as those who use it eat about half their normal energy intake but feel full. Cons: It’s hard to follow and meal preparation can take a long time. Eating out can be hard as even vegetarian meals are usually cooked. Contrary to the proponents who say cooking can destroy vitamin, minerals and other nutrients some foods are more bioavaliable when cooked. These include lycopene in tomatoes. Other vegetables that deliver more nutrients when cooked include kale, carrots, spinach, mushrooms, asparagus, cabbage and peppers. Cooking meat improves digestibility and destroys some pathogens. What about Raw Foods and Athletes? The biggest concern with raw food diets is getting enough energy to train and recover. The other major issue is how to get enough protein so important for muscle repair and growth. Finally, for female athletes, especially older female athletes, raw food diets have been shown to compromise bone mineral density. Research has shown that athletes who consume raw food diest may have shortfall of calcium, iron and vitamin B12 so supplementation may be needed.
  2. Gluten-Free Diet. When current number 1 tennis player Novak Djokovic claimed his ranking was due to this diet, athletes jumped on board. This diet is critical for for the health of people with celiac disease, an autoimmune disease that damages the small bowel and is triggered when gluten is eaten. Gluten is a protein found in wheat, barley, rye and oats and their associated products. This condition effects 1 in 133 americans and 1 in 70 Australians. Recently, researchers have shown some people suffer from nonceliac gluten insensitivity may also benefit from this diet. The food industry has jumped onto this desire to eat gluten-free foods even though people these people don’t have celiac disease or nonceliac gluten sensitivity! Premise: Gluten cannot be digested by a small percentage of the population and thus be eliminated from the diet for good health in those people. Promises: For people with celiac disease or nonceliac gluten sensitivity the diet promises weight loss and good health. Pros: Eliminating gluten found in wheat, rye, barley, oats and semolina and spelt improves symptoms (diarrhoea, constipation, nausea, vomiting, flatulence, cramping, bloating, abdominal pain and others) in these people. Alternative carbohydrate and thus energy-providing alternatives for these individuals include rice, corn, quinoa, millet, potatoes and tapioca. Cons: Athletes without gluten intolerance may be restricting variety and energy-rich options in their diet. Their is NO evidence that a gluten-free diet will enhance weight loss, indeed it may lead to weight gaingiven many gluten-free products coantain higher amounts of fat, sugar and energy than gluten-containing foods. Are we being conned is the question with research from suggesting the biggest market in gluten-free products is in those without celiac disease or nonceliac gluten sensitivity? What about the Gluten-Free Diet and Athletes? Athletes on this diet may not get enough of the important energy-producing carbohydrates to fuel training and competition. Gluten-free products may often contain a lot of sugar and fat not suited to performance in training and racing. Athletes who suffer from celiac disease or nonceliac gluten sensitivity should work with a sports dietitian. Gluten-free does not mean healthier athletes.
  3. The Fast Diet: Doctor and journalist Michael Mosley recently introduced this diet that suggests intermittent fasting two days a week when males should eat 600 calories on those days and females 500 calories. Premise: This 5:2 diet (5 days normal diet, 2 fasting) can lead to weight loss and reduce the risk of chronic disease. Promises: Weight loss and protection against cardiovascular disease and cancer. Pros: The reduction in calories on the fasting days (usually spread over the week) does lead to weight loss if energy intake is held constant on the other 5 days. Some research also suggests mood enhancement on the fasting days as well as reduction in rheumatoid arthritis sysmptoms. Cons: Research is yet to show weight loss or reduction in disease symptoms with intermittent fasting. This diet is also not recommended for pregnant or lactating women or people with diabetes. For athletes, the biggest issue is not getting enough energy for training. What about the Fast Diet and Athletes? Athletes in training need carbohydrate, protein and fat to meet training demands, especially hard training. If wanting to use this diet, fast on rest or low volume/intensity days.
  4. The Paleo Diet. This was the most ‘googled’ diet search term in 2013! The paleo diet is ‘cross-promoted’ by CrossFit, one of the many new crazes to hit the fitness industry! The basis of the diet is to eat meat and vegetables, nuts and seeds, some fruit, little starch and no sugar. Premise: Modern consumerism has seen us move towards processed foods. Returning to the diet of our caveman ancsetors will restore health and reduce the incodence of chronic disease. Promises: The diet promises weight loss, improved health, preventaion of modern chronic diseases, and an eating plan better matched to our biology. Pros: It encourages the eating of lean protein-rich foods such as wild game, grass-fed beef and fish. These foods are loer in saturated fats than most farm-raised protein-rich foods. The diet also encourages the eating of greeh and non-starchy vegetables, fruit, nuts and the plant-based oils from olives, coconut and grapeseed. The diet is also high in dietary fibre and low in sugar and salt. Cons: It’s not asy to find totally organic foods including wild game. These foods are also relatively expensive. The diet also criticizes the use of foods that come from modern agriculture including wheat, oats and barley, legumes and nuts. Some of these foods are also enriched or fortified with nutrients such as iron, niacin, thiamin and riboflavin that are needed for energy production pathways and thus important for athletes. What about the Paleo Diet and Athletes? Avoiding grains, dairy foods and starchy vegetables make it hard for athletes, especially endurance and team sport or internmittent sport athletes (tennis, squash) to get the all-important carbohydrates and nutrients they need for energy production. Female athletes may also miss out on their calcium needs, especially if pregnant or lactating.


All weight loss diets such as these four will help you lose weight, especially in the short term. However, like all fad diets like these, research has shown that longer term people almost invariably return to their normal or slightly modified diet. If you are an athlete who trains regularly, my advice is to ensure you work with an accredited sports dietitian to ensure you are getting the energy and nutrients you need to train and perform. They can also advise you as to the ‘ideal’ weight for you and your sport or event. Finally, I’d like to finish with a quote from a recent article on diet fad that appeared in the Journal of the American Medical Association. For me it says it all: “the ongoing diet debate exposes the public to mixed messages…..that heavily reinforces a fad diet industry that derives billions of dollars from a nation that is not getting healthier”. The solution is not the latest and greatest fad diet but a well-balanced diet that focuses on your training needs, your body weight, your gender and your age. For the most-detailed discussion on nutritional needs of the masters athlete, see Chapter 16 of my book The Masters Athlete. Chapter 17 of the same book also presents the only scientifically-based chapter I have seen on Weight Control and the Masters Athlete.

Sources: 1. Rosenbloom, C. (2014). Popular diets and athletes. Nutrition Today, 49(5): 244-248. 2. Pagoto, S. and Applehans, B. (2013). A call for an end to the diet debates. Journal of the American Medical Association, 310(7): 8687-8688.


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