What Pediatricians Say About Intermittent Fasting and Other Diet Trends for Teens

Dieting trends have been around for decades. From keto to the carnivore diet, anything seems to go when it comes to losing weight. Intermittent fasting is the newest trend circulating on social media, and it's garnering mixed reactions. While fad diets come and go, it seems that fasting is forever, and not in a good way.

Intermittent fasting may have some health benefits for full-grown adults, but unfortunately, they're not the ones scrolling TikTok all the time. Few doctors recommend fasting for kids and teens who are still developing, but that hasn't kept them from cutting out meals. To get the full scope of the issue, we speak with Dr. Annie DePasquale, Board-Certified Family Medicine Physician and Founder/CEO of Collaborating Docs.

The “Eat, Fast, and Live Longer” Movement

Fasting has been around far longer than many social media platforms. It gained worldwide attention after British journalist Michael Mosley premiered his documentary “Eat, Fast, and Live Longer.” His method, known as the 5:2 diet, is still followed by many people today.

The diet requires two days of low-calorie, or “low energy” intake of 600 calories or less, followed by five days of no restrictions. At the time, there was little research on the diet or its health benefits, particularly for teens. By 2017, that began to change. Natalie Lister, who worked with obese teens at her clinic in Sydney, decided to test out a theory.

The study began with 141 kids and teens following the 5:2 diet. Instead of 600 calories, some were restricted to 800 calories for 2 days per week, while others were limited to 600-700 calories, with four unrestricted days. Their control group was permitted the recommended 1,400-1,700 calories per day.

The study revolved around kids and teens with obesity-related health problems, with Lister's goal to determine if fasting could be beneficial. By the end of the study, the results were inconclusive. Both groups had minimal weight fluctuations, minor improvements in liver function, and reduced insulin resistance. However, one study member needed their gallbladder removed, an issue that was potentially related to intermittent fasting.

Intermittent Fasting on Social Media

Today, fasting is all over the internet. There are thousands of TikToks encouraging meal-skipping and low-calorie intake, and numerous Facebook posts boasting the benefits of smaller portions. While fasting has shown some benefit for full-grown adults, for kids and teens, it's a different story.

“Intermittent fasting usually means cycling between periods of eating and not eating for a set number of hours. While adults may benefit from structured fasting under proper supervision, it’s not appropriate for children or teens who are still growing,” Dr. DePasquale shares with us.

“Kids and adolescents need steady nutrition to support brain development, hormonal balance, and healthy metabolism. Restricting meals or calories at that age can lead to fatigue, poor concentration, mood swings, and even disordered eating patterns later on.”

In her practice, Dr. DePasquale has even seen firsthand the effects that social media's fasting recommendations can have on children. Teens are especially prone to try it, due to added pressure from the media and those they follow.

When asked if she's seen the uptick in the trend, Dr. DePasquale says, “Yes, absolutely. Intermittent fasting has become trendy thanks to influencers and celebrity wellness routines, and I’ve noticed more parents asking whether it’s safe for their teens.” She adds that data on fasting for adults is still emerging, and what's available right now oversimplifies complex nutrition science.

Fasting Can Cause More Health Issues For Teens

When it comes to fasting, there are two things to consider: mental and physical health. Depriving oneself of food also means nutritional deprivation. Without these essential nutrients, teens, whose bodies are still growing, may find themselves deficient. Over time, this can lead to serious health issues, especially combined with weight loss.

Mental health is another thing that suffers when fasting is left unchecked. Kids and teens are vulnerable as they grow and learn, and often compare themselves to others. As they lower their calorie intake, they may also feel low self-esteem, lower confidence, and, in severe cases, anxiety and depression. Often, what we see on social media is instant gratification — not the long process it took for the person posting the video to reach their goals.

Dr. DePasquale echoes this, underscoring how detrimental fasting can be for anyone still developing. “There’s no proven health benefit for children or adolescents to fast, and plenty of potential downsides. Frequent fasting can disrupt metabolism, delay puberty, and trigger nutrient deficiencies,” she says.

“It can also create an unhealthy relationship with food, especially for teens exposed to diet culture online. Instead, families can emphasize mindful eating: paying attention to hunger cues, portion balance, and reducing sugary drinks or processed foods.”

Fasting for Adults vs. Fasting for Teens

A recent study by researchers from Helmholtz Munich, the Technical University of Munich, and LMU Hospital Munich found that fasting can have profound effects in both adults and adolescents. They tested chronic fasting in adult and young mice to determine the overall impact after a trial period. The results, published in February 2025, painted a clear picture.

The adult and elderly mice in the test group experienced positive benefits from fasting. This included increased insulin sensitivity, which is crucial in regulating blood sugar levels. However, the young mice in the test group showed a decline in their beta function, leading to reduced insulin production and long-term adverse effects on metabolism.

Dr. Pasquale emphasizes that there are few, if any, cases where fasting would be recommended for this reason. “In medicine, fasting is rarely used as a treatment for minors. The few exceptions, such as short fasts under medical supervision for certain metabolic conditions or lab testing, are very specific and guided closely by a physician,” she says.

“Outside of those rare cases, fasting usually causes more harm than good for kids and teens. The focus should be on balanced, nutrient-dense meals and consistent eating habits.”

Age Has Everything to Do With Fasting Effectiveness

Although the study showed promising results for adults, the effects of fasting require further testing. After further analysis, researchers discovered that beta cell impairment in young mice led to failure to mature. These results are deeply concerning and could have devastating consequences for young children, not just the mice in the study.

This analysis also led researchers to conclude that the impaired beta cells showed similarities to type 1 diabetes, further raising concerns from experts. This, combined with the binge eating that sometimes results from chronic fasting, can lead to further health complications. This puts strain on anyone's body, especially an adolescent who is still maturing.

“Our study confirms that intermittent fasting is beneficial for adults, but it might come with risks for children and teenagers. The next step is digging deeper into the molecular mechanisms underlying these observations. If we better understand how to promote healthy beta cell development, it will open new avenues for treating diabetes by restoring insulin production,” says Stephan Herzig, Director of the Institute for Diabetes and Cancer at Helmholtz Munich and a professor at TUM.

While this study shows that fasting has adverse physical effects on adolescents, there are also mental ramifications to consider. Fasting breeds an unhealthy relationship with food, and can also cause headaches, mood changes, and contribute to eating disorders further down the line.

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