New research debunks myths about intermittent fasting
Despite its popularity and a large body of research supporting its safety, several myths about fasting persist.
Intermittent fasting is a popular weight loss method that doesn't require counting calories. Despite its popularity and a large body of research supporting its safety, several myths about fasting persist.
These myths suggest that intermittent fasting can lead to poor diet choices, loss of lean muscle mass, eating disorders, and decreased sex hormones. Researchers at the University of Illinois Chicago (UIC) have addressed these concerns in a new commentary published in Nature Reviews Endocrinology.
Lead author Krista Varady, a professor of kinesiology and nutrition at UIC, has been studying intermittent fasting for two decades. "I’ve been studying intermittent fasting for 20 years, and I’m constantly asked if the diets are safe," Varady said. "There is a lot of misinformation out there. However, those ideas are not based on science; they’re just based on personal opinion.”
Types of Intermittent Fasting
There are two main types of intermittent fasting:
Alternate-Day Fasting: People alternate between days of eating a very small number of calories and days of eating freely.
Time-Restricted Eating: People eat what they want within a four- to ten-hour window each day and fast for the remaining hours.
The researchers concluded that both methods are safe, debunking several myths.
Myth 1: Intermittent Fasting Leads to a Poor Diet
Some believe that intermittent fasting leads to poor diet choices. However, studies show that the intake of sugar, saturated fat, cholesterol, fiber, sodium, and caffeine does not change during fasting periods.
Additionally, the percentage of energy consumed from carbohydrates, protein, and fat remains consistent. This evidence suggests that intermittent fasting does not negatively impact diet quality.
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Myth 2: Intermittent Fasting Causes Eating Disorders
Concerns have been raised that intermittent fasting might trigger eating disorders. The researchers found no evidence to support this claim. None of the studies reviewed indicated that participants developed eating disorders due to fasting.
However, it is important to note that all studies screened out individuals with a history of eating disorders. The researchers caution that those with such a history should avoid intermittent fasting. They also advise pediatricians to closely monitor obese adolescents who may be at higher risk of developing eating disorders if they start fasting.
Myth 3: Intermittent Fasting Causes Loss of Lean Muscle Mass
Another common myth is that intermittent fasting leads to an excessive loss of lean muscle mass. The research shows that people lose the same amount of lean muscle mass whether they lose weight through fasting or other diets.
In both scenarios, resistance training and increased protein intake can help counteract the loss of lean muscle. This indicates that intermittent fasting does not uniquely contribute to muscle loss.
Myth 4: Intermittent Fasting Affects Sex Hormones
There are concerns that intermittent fasting might impact sex hormones, affecting fertility and libido. However, the researchers found no evidence to support this. Studies show that fasting does not affect levels of estrogen, testosterone, or other related hormones. This suggests that intermittent fasting does not negatively impact reproductive health or sexual function.
The UIC researchers' commentary provides a thorough review of the myths surrounding intermittent fasting. Their conclusions, based on a combination of their own clinical studies and those conducted by others, offer reassurance about the safety of intermittent fasting.
Krista Varady and her colleagues, Vanessa Oddo, Sofia Cienfuegos at UIC, and Shuhao Lin, now at the Mayo Clinic, have contributed to clarifying the misconceptions about this popular dietary practice. As Varady noted, "There is a lot of misinformation out there. However, those ideas are not based on science; they’re just based on personal opinion.”
The evidence supports that intermittent fasting is a safe and effective method for weight loss without the risks suggested by common myths. With proper guidance and consideration of individual health histories, intermittent fasting can be a beneficial approach to achieving and maintaining a healthy weight.
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