Intermittent fasting: Researchers debunk 4 common myths

For this study, Varady and her team analyzed the findings from previous studies to disprove four common myths about intermittent fasting and found that intermittent fasting:

• does not lead to a poor diet
• does not cause eating disorders
• does not cause excessive loss of lean muscle mass
• does not affect sex hormones

“I’ve been studying intermittent fasting for 20 years, and I’m constantly asked if the diets are safe,” Varady said. “I’ve noticed that there is a lot of misinformation out there (on social media, websites, etc). We wrote this article to point out that those ideas are not based on science; they’re just based on personal opinion.”

“I wasn’t surprised by the findings,” she continued. “Since I’ve been studying intermittent fasting for so long, I knew that these common misconceptions were untrue. We wrote this paper to show the scientific data to support that these myths are not true.”

Varady said she thinks these findings will help doctors and dietitians feel more secure about prescribing intermittent fasting to their patients.

“They can use this paper to understand that a lot of the common myths around the safety of intermittent fasting are not based on scientific research,” she noted. “Intermittent fasting is overall a safe diet therapy for weight loss in a variety of patient groups.”

A person following an intermittent fasting diet has periods during the day or the week where they completely fast or eat a very small amount of calories.

For example, a person following the 16:8 method fasts for 16 hours and eats for 8 hours each day. If following the 12:12 plan, they would abstain from eating for 12 hours — basically overnight — and have a 12-hour eating window during the day. The 5:2 intermittent fasting plan calls for eating normal amounts of food five days a week and then only eating up to 500–600 calories two days a week.

After reviewing this study, Mir Ali, MD, a board certified bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA, told MNT he was not surprised by its findings.

“What I found with people who are doing intermittent fasting and it’s working for them (is) that they don’t seem to have a lot of problems — they’re not worried about malnutrition, not worried about muscle loss,” Ali explained. “As long as they’re doing the right things and that’s true with any kind of diet or exercise plan – you still need to get the nutrition your body needs to maintain muscle and prevent vitamin losses and other things.”

“For some people, it works really well and you have to try different methods. [For] some people the 10 or 12-hour daily fast is what works for them, other people would see every other day fasting. So not one thing works for every person — it’s more trying out what fits their needs and their lifestyle.”

— Mir Ali, MD, bariatric surgeon

Monique Richard, a registered dietitian nutritionist and owner of Nutrition-In-Sight, noted that research studies are limited in their ability to be able to take the results and provide blanket generalizations to every single person. Richard was not involved in this study.

“We are each singular and while many observations can be made for the general masses, or majority, there will always be outliers to whom the information does not apply, or applies differently,” Richard explained to MNT. “The point here is to understand the nuance of what is being said, to what is being tested, to what is being applied to a sample of one — you.

“Therefore the most beneficial recommendation to figure out if intermittent fasting would be safe, beneficial, and conducive to overall health would be to work with a registered dietitian nutritionist (RDN) or other qualified nutrition professional and your healthcare team,” she continued.

“An RDN takes into account an individual’s goals but also digs deeper to understand how the individual’s current health, activity level, genetics, nutritional and energy needs and lifestyle factors may play into the overall picture.”

“For many people, for many reasons — blood sugar regulation, mental clarity, energy, nutrient need adequacy being met, satisfaction, fulfillment, enjoyment, social connection — the intermittent fasting, time-restricted dietary pattern works well. However, the quality, composition, and frequency of what is being consumed still needs to be assessed appropriately and prioritized. Variations of intermittent fasting are not a ‘cheat-day-free-for-all’ since that can be counterproductive to health, optimal digestion, absorption, and organ function, including psychological and cognitive health.”

— Monique Richard, registered dietitian nutritionist