Key takeaways
- Adult equations leave out growth, and teenagers of the same age can be years apart in development.
- Typical needs are about 1,800 to 2,400 kcal for girls aged 14 to 18 and 2,000 to 3,200 kcal for boys, depending on age and activity.
- Paediatricians advise against dieting in adolescence because it is linked to later weight gain and to eating disorders.
- Teen athletes need enough food for growth and training; missed periods, frequent injuries and constant tiredness are warning signs.
On this page
- Why adult calculators don’t fit teenagers
- How many calories do teenagers need?
- Growth spurts and appetite
- Why dieting is risky while you’re still growing
- Teen athletes: eat enough to grow and train
- Building muscle as a teenager
- If you’re worried about your weight
- Healthy habits at any size
- Advice for parents and carers
- When can a TDEE calculator be used?
- Questions about TDEE for teenagers
Why adult calculators don’t fit teenagers
The Mifflin-St Jeor equation that most TDEE calculators use was developed from measurements of adults aged 19 to 78. It predicts resting metabolism from weight, height, age and sex, on the assumption that your body has stopped growing. Teenagers break that assumption in several ways:
- Growth costs energy. Building bone, muscle and other tissue during puberty needs energy and nutrients on top of normal daily needs.
- Bodies change quickly. Height, muscle and fat can change a lot within a year, so a number that fits today may not fit in six months.
- Development varies hugely. Two 14-year-olds can be several years apart in puberty, with very different needs.
- Activity swings widely. A teenager who trains for a sport most days can burn far more than a classmate who doesn’t, and seasons change it again.
An adult equation can therefore be badly wrong for a teenager, in either direction. A number that is too low is the bigger risk, because it can push a growing body towards eating too little. That is why our calculators ask for an age of 18 or over.
How many calories do teenagers need?
The 2020 to 2025 US Dietary Guidelines give estimated calorie needs for young people of average size by age, sex and activity level:
| Age and sex | Sedentary | Moderately active | Active |
|---|---|---|---|
| Girls, 14 to 18 | 1,800 | 2,000 | 2,400 |
| Boys, 14 | 2,000 | 2,400 | 2,800 |
| Boys, 15 | 2,200 | 2,600 | 3,000 |
| Boys, 16 to 18 | 2,400 | 2,800 | 3,200 |
In these guidelines, sedentary means only the light activity of everyday life, moderately active adds the equivalent of walking about 2.4 to 4.8 km (1.5 to 3 miles) a day at a brisk pace, and active means more than that. Teenagers who train hard for a sport most days may need more than the top of the table.
These are averages for planning meals, not targets to hit. A growing teenager’s appetite is usually a better day-to-day guide than any number, as long as meals are regular and mostly made of nourishing food.
Growth spurts and appetite
Many parents notice that their teenager suddenly seems hungry all the time. That is normal. Growth spurts, which usually come earlier for girls than for boys, raise energy needs, and appetite rises to match. Some teenagers also put on a little weight before a growth spurt and then grow into it. Short-term changes like these are part of normal development and are best discussed with a doctor before anyone reacts to them.
Why dieting is risky while you’re still growing
The American Academy of Pediatrics (AAP) has looked closely at how to prevent both obesity and eating disorders in teenagers, and its advice is the same for both: don’t diet. Its clinical report advises paediatricians to discourage dieting, skipping meals and diet pills, and points out that dieting in adolescence is associated with later weight gain as well as with eating disorders. The focus, it says, should be on a healthy lifestyle rather than on weight.
There are other reasons to be careful. The teenage years are when a large share of the body’s bone strength is built, which takes enough energy, protein, calcium and vitamin D. Eating too little can delay growth and puberty, disrupt periods and leave a teenager tired and struggling to concentrate.
Teen athletes: eat enough to grow and train
Teenagers who play sport have to fuel two things at once: growth and training. When they don’t eat enough for both, the result is low energy availability. The International Olympic Committee’s consensus statement on Relative Energy Deficiency in Sport (REDs) describes how it can affect periods, bone health, growth, mood, immunity and performance, in boys as well as girls. Warning signs include:
- missed, irregular or delayed periods;
- repeated injuries or a stress fracture;
- constant tiredness, frequent illness or falling performance;
- weight loss, or not growing as expected;
- anxiety about food or a need to exercise to “earn” meals.
If you notice these, speak to a doctor. In the meantime, regular meals and snacks around training, with carbohydrate for energy and a protein food at each meal, cover most of what a young athlete needs. Weight-class and appearance-focused sports deserve extra care, and any attempt to make weight should be supervised by a professional.
Building muscle as a teenager
Strength training with good coaching is a healthy part of growing up and can start well before 18. Growth itself already raises energy needs, so there is no need for “bulking” with very large amounts of food. Three to four regular meals that each include a protein food, such as eggs, milk, yoghurt, meat, fish, beans or lentils, plus snacks around training, usually provide plenty. Protein powders and other supplements are rarely needed and are best discussed with a doctor or sports dietitian.
If you’re worried about your weight
If you are a teenager who is unhappy with your weight, talk to a parent, carer or another adult you trust, and see your doctor. Please don’t set yourself a calorie target or follow an adult diet plan. A doctor can look at your growth over time, which tells them far more than one weight or one BMI, and can check for health problems.
For teenagers who do have obesity, the AAP’s 2023 clinical practice guideline recommends treatment led by health professionals, built on family-based changes to eating, activity and daily habits, rather than self-directed dieting. Doctors may also discuss other options for some older teenagers. The point is that this is done with support and monitoring, not alone.
Healthy habits at any size
- Regular meals, including breakfast, rather than skipping meals and making up for it later.
- A protein food and some fruit or vegetables at most meals.
- Water as the main drink, with sugary drinks kept for occasionally.
- About an hour of activity a day, the World Health Organization’s guidance for young people, ideally including things they enjoy.
- Eight to ten hours of sleep, as recommended for 13- to 18-year-olds, with screens put away before bed.
- Family meals where possible, which the AAP encourages.
Advice for parents and carers
The AAP’s advice for families is practical:
- Talk about health, not weight. Encourage eating well and being active for strength, energy and mood. Avoid comments about your teenager’s weight or body, and try not to criticise your own body in front of them.
- Eat together as often as you can, and keep nourishing food easy to reach at home.
- Be a role model for regular meals, activity and sleep.
- Don’t encourage dieting, even with good intentions.
- Watch for warning signs of an eating disorder: skipping meals, strict food rules, cutting out whole food groups, secretive eating, excessive exercise, rapid weight change or missed periods.
If you are worried, act early. Speak to your GP or family doctor. In the UK, the eating disorder charity Beat offers support for families; in the US, the National Alliance for Eating Disorders runs a helpline.
When can a TDEE calculator be used?
From 18, adult equations apply, and our calculators can be used. Some young adults are still filling out into their early twenties, so treat the result as a starting point, eat well rather than restrictively, and check it against real-life weight trends.
Questions about TDEE for teenagers
Can teenagers use a TDEE calculator?
Adult TDEE calculators aren’t designed for teenagers because they leave out the energy needed for growth. Our calculators only accept ages 18 and over. A doctor or registered dietitian can advise on a teenager’s needs.
How many calories does a teenager need a day?
US guidelines estimate about 1,800 to 2,400 kcal for girls aged 14 to 18 and about 2,000 to 3,200 kcal for boys, depending on age and activity. Teen athletes may need more.
Should teenagers count calories?
Generally no. Paediatricians advise against dieting in adolescence. Regular meals, a protein food and fruit or vegetables at most meals, activity and sleep are a better focus.
Is it safe for teenagers to lift weights?
Yes, with good coaching and sensible progression. Strength training is a healthy activity for teenagers and doesn’t need special diets or supplements.
Do teenage athletes need protein shakes?
Rarely. Regular meals that each include a protein food usually provide enough. Talk to a doctor or sports dietitian before using supplements.
How can I tell if my teenager is eating enough?
Steady growth, regular energy and normal periods in girls are good signs. Tiredness, frequent injuries, weight loss or missed periods are reasons to see a doctor.
My teenager wants to lose weight. What should I do?
Listen, avoid comments about their body, and book an appointment with your doctor together. Focus at home on family meals, activity and sleep rather than a diet.
Sources
- Golden NH, Schneider M, Wood C; Committee on Nutrition, Committee on Adolescence, Section on Obesity. Preventing obesity and eating disorders in adolescents. Pediatrics. 2016;138(3):e20161649. doi.org/10.1542/peds.2016-1649
- Hampl SE, Hassink SG, Skinner AC, et al. Clinical practice guideline for the evaluation and treatment of children and adolescents with obesity. Pediatrics. 2023;151(2):e2022060640. pubmed.ncbi.nlm.nih.gov/36622115/
- US Department of Agriculture and US Department of Health and Human Services. Dietary Guidelines for Americans, 2020 to 2025. 9th edition. December 2020. www.dietaryguidelines.gov/
- Mountjoy M, Ackerman KE, Bailey DM, et al. 2023 International Olympic Committee’s (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). Br J Sports Med. 2023;57(17):1073-1097. pubmed.ncbi.nlm.nih.gov/37752011/
- Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-1462. doi.org/10.1136/bjsports-2020-102955
- Paruthi S, Brooks LJ, D’Ambrosio C, et al. Recommended amount of sleep for pediatric populations: a consensus statement of the American Academy of Sleep Medicine. J Clin Sleep Med. 2016;12(6):785-786. doi.org/10.5664/jcsm.5866
- Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247. doi.org/10.1093/ajcn/51.2.241