Intermittent Fasting (IF) is the practice of cycling through periods of not eating and eating or “feasting.” Fasts may last anywhere from hours to days. IF is thought to decrease the body’s reliance on carbohydrates and increase the use of fatty acids as fuel, thus promoting the breakdown of stored fat. The buzz around this pattern of eating is rapidly increasing, but consider the big picture before heeding the hype when deciding whether or not IF is right for you . . .

Hype: Health claims associated with IF include improved glucose control, increased energy levels, decreased inflammation, enhanced brain function, reduced risk of cancer and other chronic diseases, and more.

Big Picture: Many claims are based on animal studies (specifically mice), and even those studies have mixed results with no clear conclusions. The American Journal of Clinical Nutrition states that while a “few randomized controlled trials and observational clinical outcomes studies support the existence of a health benefit from fasting, substantial further research in humans is needed before the use of fasting as a health intervention can be recommended.”

Hype: Weight loss is possible with intermittent fasting.

Big Picture: With weight loss, individuals may also experience loss of muscle. Furthermore, when the body is inadequately nourished, physiological adaptations can occur leading to slower metabolism, which creates the potential for weight gain. On the flip side, eating regularly may help with maintenance of lean body mass and a healthy metabolism.

Hype: Intermittent Fasting does not require purposeful calorie counting or restriction.

Big Picture: Going long periods without eating can lead to feeling ravenously hungry, which may result in overeating or binging during “feasting” periods. The opposite may also happen as excessive fasting or restriction can lead to nutrient deficiencies and electrolyte abnormalities. Eating every 3-5 hours throughout the day tends to stabilize insulin and blood glucose, preventing overeating at the end of the day or during feasting periods.

Hype: Intermittent Fasting is easy to implement.

Big Picture: What about those times it interferes with social aspects of eating (i.e. everyone is going out to lunch and you’re not)? Though IF may sound simple, it may not be so easy to function during fasts due to low energy, changes in mood, and decreased productivity. 

Do Not Try Intermittent Fasting If . . .

  • You are not eating a balanced diet, getting adequate sleep, and managing chronic stress. Take time to assess and adjust your current habits before proceeding. Even promoters of IF recommend dialing in food quality and balance for several weeks before fasting. Ironically, they also recommend listening to your body (though “Intermittent Fasting” and “listening to your body” sounds like an oxymoron to me). 
  • You’re training most days of the week. Consistent, adequate fuel is needed to support workouts and to prevent illness or injury.
  • You have diabetes, irritable bowel syndrome (IBS), or other chronic health conditions that may be of concern. IF has been linked to women’s health issues including reproductive health, bone formation, and metabolic activity. Speak to a Registered Dietitian and physician before starting any new diet.
  • You have a personal or family history of disordered eating. Sadly, many of the articles about managing side effects of IF could be titled “How to Have an Eating Disorder.”
  • It would add stress (which would likely compound the original problem).
  • You do not feel well going long periods without eating.

To Sum It Up . . .

Any eating plan that encourages people to work against their own internal cues of hunger and satiety is likely to be unsustainable. For that reason, the associated risks and lack of conclusive research, IF is not a practice I’d recommend to my clients.

Blair Mize, MS, RDN, CSSD, LDN is co-owner of Memphis Nutrition Group, a nutrition & lifestyle counseling practice operated by registered & licensed dietitians/nutritionists. Memphis Nutrition Group believes in a non-diet approach that promotes overall health and optimal performance without compromising the enjoyment of food. For more information call Memphis Nutrition Group at 901.343.6146 or visit