Researchers debunk myths about intermittent fasting, confirming its safety and effectiveness in not altering diets, causing eating disorders, losing muscle mass, or affecting sex hormones through rigorous clinical studies.
In a recent article, researchers from the University of Illinois Chicago have debunked four common misconceptions regarding the safety of intermittent fasting.
Intermittent fasting has become an increasingly popular way to lose weight without counting calories. A large body of research has shown it’s safe, yet several myths about fasting have gained traction among clinicians, journalists, and the general public: that fasting can lead to a poor diet or loss of lean muscle mass, cause eating disorders, or decrease sex hormones.
In a new commentary in Nature Reviews Endocrinology, UIC researchers debunk each of these misconceptions, basing their conclusions on clinical studies, some of which they conducted and some done by others.
“I’ve been studying intermittent fasting for 20 years, and I’m constantly asked if the diets are safe,” said lead author Krista Varady, professor of kinesiology and nutrition at UIC. “There is a lot of misinformation out there. However, those ideas are not based on science; they’re just based on personal opinion.”
Types and Safety of Intermittent Fasting
There are two main types of intermittent fasting:
- Alternate-Day Eating: People alternate between days of consuming a very small number of calories and days of eating what they want.
- Time-Restricted Eating: People eat what they want within a four- to 10-hour window each day and refrain from eating for the rest of the day.
The researchers conclude that both types are safe despite popular myths. Here are their conclusions:
- Intermittent fasting does not lead to a poor diet: Studies show that the intake of sugar, saturated fat, cholesterol, fiber, sodium, and caffeine does not change during fasting compared to before a fast. The percentage of energy consumed from carbohydrates, protein, and fat remains consistent as well.
- Intermittent fasting does not cause eating disorders: None of the studies indicate that fasting caused participants to develop an eating disorder. However, all the studies excluded participants with a history of eating disorders. Researchers advise that those with such a history should not attempt intermittent fasting. Additionally, they urge pediatricians to monitor obese adolescents carefully if they begin fasting, as this group has a high risk of developing eating disorders.
- Intermittent fasting does not cause excessive loss of lean muscle mass: Studies indicate that people lose the same amount of lean muscle mass whether they lose weight by fasting or with a different diet. In both cases, resistance training and increased protein intake can counteract the loss of lean muscle.
- Intermittent fasting does not affect sex hormones: Despite concerns about fertility and libido, neither estrogen, testosterone, nor other related hormones are affected by fasting, according to the researchers.
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