This page is for parents wondering whether intermittent fasting is safe for teenagers. The short answer: it is not recommended. Structured fasting for weight loss or “health” is not appropriate for adolescents except under specialist medical care. Teenagers see a lot of fasting content online, however, and some may already be trying it, so it helps to understand why.
This guide explains why fasting is not recommended for teens, the specific risks (especially for eating disorders), what to do if your teenager wants to fast, the difference between normal flexible eating and structured fasting, and warning signs to take seriously.
Table of Contents
Why Fasting Is Not Recommended for Teens
Paediatric and dietetic guidance generally discourages dieting and meal-skipping in adolescents, and fasting protocols are designed and studied for adults. The main reasons:
- Teenagers need plenty of energy and nutrients to support growth and development
- Dieting and meal-skipping in adolescence have been linked with a higher risk of disordered eating
- Rigid food rules learned in the teenage years can be hard to shake later
- There is very little research on fasting in teenagers, and no evidence that healthy teens benefit from it
- The potential harms outweigh any likely benefit
The Growth and Development Issue
The adolescent body is doing significant developmental work:
- Growth in height (continues into the mid-to-late teens for most)
- Building bone: a large share of adult bone mass is laid down during adolescence, with peak bone mass reached in early adulthood
- Muscle mass development
- Brain development continues into the mid-20s
- Sexual maturation and reproductive system development
- Metabolic system maturation
All of this depends on consistent energy and nutrient intake. Shorter eating windows often reduce overall intake, even when that is not the intention. Under-eating during these years can have lasting effects, particularly on bone, because bone built in adolescence helps protect against fractures later in life.
The Eating Disorder Risk
This is the most important section. Eating disorders most often begin in adolescence and early adulthood. Several factors can combine:
- Body image pressure
- Social media exposure to diet/wellness content
- The rigid structure of fasting protocols
- The reward of feeling “in control” of eating
- A stage of life when habits and self-image are still forming
Together these create real risk. Research has linked dieting and meal-skipping in adolescents with a higher likelihood of later disordered eating, and intermittent fasting can make food restriction look like a healthy lifestyle choice rather than a warning sign.
For a teenager already struggling with body image or showing signs of disordered eating, fasting rules can become the structure within which an eating disorder develops. See our page on the psychology of fasting for more on unhealthy patterns.
The Few Exceptions
A few situations may involve fasting or structured eating patterns in teenagers:
- Weight management for severe obesity with related health problems, only as part of a specialist programme
- Type 2 diabetes, where any change to eating pattern must be managed with the teen’s diabetes team
- Religious fasting traditions, which often include accommodations for young people
- Fasting before surgery or medical procedures, as instructed by the care team
None of these are a basis for self-directed fasting based on internet content. Any medical use involves specialist supervision precisely because the risks in adolescents are higher.
What to Do If Your Teenager Wants to Fast
The conversation matters more than the rule.
Listen first
Why does your teenager want to fast? Common reasons include weight concerns, social media, friends, curiosity about a trend, sports performance, or, more worryingly, early disordered eating thoughts.
The reason behind the request shapes the response. Curiosity about a trend is different from active body-image distress.
Don’t make food the battleground
Strict prohibitions can backfire by creating secret eating patterns. The goal is open conversation about why fasting isn’t the right tool for this stage of life.
Address the underlying concern
If body image is the issue, that is the conversation to have, possibly with professional support. If sports performance is the goal, nutrition advice designed for young athletes is a better path. If it is general health curiosity, age-appropriate information about balanced eating, sleep, and activity helps.
Discuss with your paediatrician
This is especially important if your teenager is persistent about fasting, has lost weight recently, or shows other concerning eating patterns. A paediatrician or family doctor can check growth and health, screen for eating disorders, and refer for specialist help if needed.
Watch for warning signs
(See the section below.) Eating disorders are generally easier to treat when caught early, so do not dismiss early signs as “just being a teenager.”
Sensible Meal Patterns vs Structured Fasting
It’s reasonable for a teenager not to eat snacks late at night, to skip a snack they’re not hungry for, or to have a 12-hour overnight gap between dinner and breakfast. None of this is “intermittent fasting” in the structured sense.
The difference between healthy meal patterns and structured fasting:
- Healthy: “I’m not hungry for breakfast today, I’ll have a bigger lunch.”
- Healthy: “I don’t feel like a snack right now.”
- Concerning: “I’m doing 16:8, I can’t eat until noon.”
- Concerning: “I’m skipping breakfast every day to lose weight.”
- Concerning: Tracking fasting hours, using fasting apps, having strict rules about when food is allowed
The structure is the issue. Flexible eating patterns are healthy; rigid eating rules in adolescents are warning signs.
Warning Signs to Take Seriously
- Increasing rigidity around food choices
- Skipping family meals
- New focus on calorie counting or food tracking apps
- Weight loss in a teen who shouldn’t be losing weight
- Loss of menstrual periods (in girls)
- Excessive exercise alongside reduced eating
- Distress when eating patterns are disrupted
- Hiding eating or hiding not-eating
- Body image preoccupation
- Mood changes alongside food changes
- Loss of social activities involving food
Any of these is worth discussing with your paediatrician or family doctor. Several together call for prompt action. Fainting, dizziness, a very slow or irregular heartbeat, rapid weight loss, or refusing food and fluids need urgent medical attention.
Frequently Asked Questions
My teenager just wants to skip breakfast. Is that fasting?
Not usually. Many teenagers are not hungry in the morning. Skipping breakfast occasionally because of low appetite is different from structured fasting. Watch the pattern: if it is flexible and they eat well at other times, it is probably fine, although a quick breakfast or a snack to take to school is still a good idea. If it is rule-based and motivated by weight loss, it is more concerning.
What about a teen athlete using intermittent fasting?
Young athletes have particularly high energy and nutrient needs. Fasting makes it easy to under-eat without meaning to, which can impair performance and recovery and raise the risk of injury and bone problems. Nutrition for young athletes is a specialist area; adult fasting advice is not appropriate.
My teen has type 2 diabetes. Should they fast?
Only if their diabetes team recommends and supervises it. Fasting can cause dangerous low blood sugar with some diabetes medications, and eating patterns for teens with type 2 diabetes should be planned with their care team.
What about religious fasting?
Religious fasting traditions vary, and many have accommodations for young people, such as shorter fasts, partial fasts, or exemptions for illness. It is generally manageable for healthy teens when approached thoughtfully, with good hydration and nutrition outside fasting hours. If your teen has a health condition or a history of disordered eating, talk to their doctor and, if helpful, a religious leader about exemptions.
I fast and my teen is asking about it. What do I say?
An honest explanation might be: “Adult bodies have finished growing; teenage bodies are still building bone, muscle, and brain. Fasting can interfere with that. As an adult, it could be an option to discuss with a doctor. Right now, eating regularly supports the growth that is happening.” It also helps to avoid talking about your own fasting in terms of weight or body shape in front of them.
What if my teen has already started fasting?
Stay calm and open the conversation. Ask why, listen carefully, and watch for warning signs of disordered eating. Talk to your paediatrician or family doctor if the pattern continues or if any concerning signs are present. If you see clear eating disorder behaviour, do not wait: early help makes a real difference. National eating disorder charities and helplines can also offer support and advice for parents.
The Bottom Line
Intermittent fasting is not recommended for teenagers. Growth and development needs and the risk of eating disorders both argue against it, and there is no evidence of benefits that would offset those risks. If your teenager wants to fast, listen for the underlying reason, address it directly (body image, sports nutrition, or general health information), watch for warning signs of disordered eating, and involve your paediatrician or family doctor if concerning patterns develop. Regular, flexible eating, typically three meals plus snacks as needed, best supports healthy development.