Myth Busting The Most Popular Fad Diets
By Page Love, MS, RDN, LD, CSSD, USPTA and Avery Lusk, MS, Dietetic Intern
As we kick off the new year, weight loss often becomes a focal point for many of us. Promises of “quick fixes” lure us with bold claims, catchy names, and the prospect of rapid results. We’ve seen firsthand how these diets can compromise health and performance. In this article, we’ll debunk popular fad diets using insights from sports science research, and we’ll provide practical, science-based nutrition strategies to help you fuel your performance.
Keto diet
The goal of the keto diet (low-carbohydrate, high-fat) is to achieve ketosis. Carbohydrates are the body’s primary energy source, so as blood glucose, the simple energy breakdown source of carbohydrates, gets critically low, the body starts to break down stored energy, or body fat stores into ketones, leading to ketosis. The process takes two to four days and can only be achieved by eating less than 50g of carbohydrates per day. This low-carb, high-fat diet results in low energy and slower movement on the court — and “hitting the wall” in longer matches!
Additionally, with the keto diet, people tend to overeat protein and consume poor-quality fats with almost no fruits and vegetables. With weight loss being the primary goal for this diet, it does show quicker results, but research also shows that most people do not maintain their weight loss. However, the diet is hard to follow and is heavy on red meat and fatty, processed foods.
The keto diet also increases risk for heat illness as higher protein intake causes increased urine production to rid the body of the excess protein it cannot use, thus causing increased water losses and less ability to cool down in the hotter months.
Intermittent fasting
To lose weight, the basic principle is to consume fewer calories than you burn. Intermittent fasting supports this by limiting the time frame in which you can eat, often to an eight-hour window, followed by 16 hours of fasting. While this is less restrictive in terms of food choices, it can result in an imbalanced intake if nutrient-dense options aren’t prioritized. This is particularly concerning for players, as energy deficits can negatively impact performance, recovery, and overall health. For example, a research trial found that endurance athletes practicing intermittent fasting experienced declines in time trial performance.
Restricting eating also poses practical challenges, such as interfering with social meal patterns and limiting opportunities to fuel for morning practices, games, or matches. The adjustment period for intermittent fasting, which lasts up to 4 weeks, often comes with side effects like hunger, low energy, and irritability. Prolonged fasting may lead to carbohydrate depletion, hyperthermia, dehydration, and a decline in endurance performance. For racquet sports, these risks are especially pronounced, as insufficient calorie intake during fasting periods can hinder both training outcomes and pre-match preparation.
Carnivore diet
The carnivore diet promotes eating only animal products while eliminating all plant-based foods. This diet claims to improve everything from weight loss to autoimmune conditions and has been endorsed by celebrities, making it hard to ignore. However, its extreme restrictions raise significant health and performance concerns. The diet eliminates essential nutrients in fruits, vegetables, and whole grains, which leads to deficiencies in fiber, vitamins, and antioxidants (carotenoids and polyphenols, which are key nutrients that help an athlete’s body heal). Over time, the carnivore diets’ high reliance on saturated fats and cholesterol increases the risk of unfavorable lipid profiles, thus increasing heart disease, digestive issues, and nutritional deficiencies. A healthier, more balanced approach includes both lean proteins and healthy carbohydrates from grains, fruits, and vegetables.
As tempting as fad diets may seem, the truth is that sustainable health, weight management, and peak athletic performance rarely come from quick fixes or extreme restrictions. An optimal sports nutrition diet emphasizes balance, variety, and timing. It includes carbohydrates for energy, protein for muscle repair and recovery, healthy fats for endurance and nutrient absorption, and plenty of fruits and vegetables for essential vitamins, minerals, and antioxidants. This approach ensures athletes have the fuel they need for training, peak performance, and recovery — benefits that fad diets often fail to deliver.
Page Love is an avid ALTA participant and sport dietitian/nutrition advisor for the WTA and ATP professional tours, serves on the USTA sport science commission, and has a private practice in Atlanta. You can reach her at nutrifitga.com. Avery Lusk holds a master’s in Nutrition from UGA and is completing her dietetic internship. She plans to become a sport dietitian.
