Debunking myths: the safety of intermittent fasting

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Intermittent fasting, a popular approach to weight loss that avoids the hassle of counting calories, has been the subject of many health debates.

Despite its growing popularity and substantial research backing its safety, some widespread misconceptions persist.

Researchers from the University of Illinois Chicago have addressed these myths in a detailed commentary published in Nature Reviews Endocrinology, aiming to clear the air about the safety of this dietary strategy.

Krista Varady, a professor of kinesiology and nutrition at the University of Illinois Chicago and the lead author of the study, has spent two decades researching intermittent fasting.

“I’m often asked about the safety of these diets,” she notes. “There’s a lot of incorrect information floating around that isn’t supported by scientific evidence but rather by personal opinion.”

Intermittent fasting typically comes in two forms: alternate-day eating and time-restricted eating. In alternate-day eating, individuals alternate between days of consuming very few calories and days of eating normally.

Time-restricted eating limits food intake to a specific window of 4 to 10 hours each day, followed by fasting for the remaining hours. The University of Illinois Chicago team confidently supports the safety of both methods, countering several common concerns.

Addressing the Myths

One of the main myths is that intermittent fasting leads to poor nutrition. However, the research team points to studies indicating that people’s intake of sugar, saturated fats, cholesterol, fiber, sodium, and caffeine remains stable during fasting periods compared to their normal eating days.

Similarly, the proportion of calories derived from carbohydrates, proteins, and fats does not significantly change while fasting.

Another concern is the potential for fasting to trigger eating disorders. The researchers clarify that their studies do not support this claim. Importantly, all study participants were screened to exclude those with a history of eating disorders.

The researchers recommend that intermittent fasting should be avoided by individuals with such a history and advise medical professionals to monitor closely if obese adolescents begin fasting, as they are at a higher risk for developing eating disorders.

The fear that intermittent fasting might cause excessive loss of muscle mass is also unfounded. Studies reviewed by the team show that the amount of muscle mass lost during weight loss is comparable between those who fast and those who follow other diets.

They suggest that resistance training and increasing protein intake can help mitigate muscle loss in any weight loss regimen.

Lastly, the impact of fasting on sex hormones has been a topic of concern, particularly regarding fertility and libido. The findings from the University of Illinois Chicago indicate that key hormones like estrogen and testosterone remain unaffected by fasting.


This comprehensive review by Krista Varady and her colleagues, including Vanessa Oddo, Sofia Cienfuegos, and Shuhao Lin (now at the Mayo Clinic), effectively challenges the myths surrounding intermittent fasting.

By backing their conclusions with data from clinical studies, the team provides reassurance about the safety of these dietary practices, emphasizing that when done correctly, intermittent fasting poses no significant risks to nutritional intake, mental health, muscle mass, or hormonal balance.

This clarity is essential for both the general public and healthcare providers to understand the real impacts of intermittent fasting, ensuring that individuals can make informed decisions about their health and diet.

If you care about weight, please read studies about diet that can treat fatty liver disease, obesity, and hop extract could reduce belly fat in overweight people.

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The research findings can be found in Nature Reviews Endocrinology.

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