By Joy Dubost, PhD, RD, CSSD
Intermittent fasting — a diet approach that restricts food and calorie-containing beverages, typically for at least 16 hours — is gaining attention for its purported weight-loss benefits. Animal studies and preliminary human studies indicate that this method might positively impact our health, possibly reducing risk factors related to diabetes, cancer and heart disease.
However, additional human studies are needed to determine any health benefits and especially comparing intermittent fasting to other calorie-restricted diets. Regardless, intermittent fasting has gained momentum and some dieters have jumped on the bandwagon.
Elite Athlete or Fitness Enthusiast
In general, prolonged fasting can be harmful to health and may negatively impact athletic abilities or exercise stamina. Yet, this is not always the case in elite athletes and is still a matter of debate. A limited number of studies have investigated the impact of athletic performance on elite athletes who observe fasting for religious purposes, such as Ramadan, during which observers abstain from food and drink from sunrise to sunset.
It's not clear to what degree intermittent fasting impacts our physical performance, or whether it impacts it at all. It also may impact everyone differently, as some people likely adapt more quickly to fasting than others. Athletes are less likely to suffer a negative impact on their performance if they maintain their total caloric and nutrient intake during non-fasting periods, training regimen, body composition and sleep schedule. Regardless, coordination of exercise and training with a coach, athletic trainer and registered dietitian nutritionist is critical for competitive athletes.
For the everyday active person, intermittent fasting may present some challenges and may not be the best approach for managing your weight. People practicing intermittent fasting may feel light-headed, dizzy, tired and nauseated, and their workouts may suffer. Consuming too few calories will make it harder to get through a tough workout. Staying well-fueled with a balanced diet of fruits, vegetables, low-fat dairy, whole grains and lean protein can optimize your performance when exercising. Making lifelong, well-balanced dietary choices also will help you get all the nutrients you need and maintain a healthy weight. Meeting with a registered dietitian nutritionist can assist in developing a personalized, dietary approach to keep you healthy and active.
Joy Dubost, PhD, RD, CSSD, is a spokesperson for the Academy of Nutrition and Dietetics.
Reviewed March 2014