Teen gym culture is booming—here’s what’s healthy, what’s not, and when to worry

As more teenagers are hitting the weights rooms, a leading physiologist explains what’s healthy, what’s safe, and what parents should watch out for.

Young boys lifting kettlebells at gym

Published: January 2, 2026 at 9:12 AM

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What is it with teenage boys and the gym? With an over-saturation of muscly men to look up to on social media, in films, and in adverts, there seems to be a new beauty standard for men, and teenage boys are feeling the pressure. And with more and more women showing up in the weights room too, teen girls are also turning to strength training to get those 'gains.'

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Whether they want to get ‘jacked,’ ‘swole,’ or just ‘huge,’ more teens than ever are opting to work out in gyms in their free time. According to a poll by UK gym group PureGym, 89% of their customers aged 18 to 24 did some kind of strength-training exercise each week, and in 2024, 29% of new gym joiners are Gen Z according to US fitness software company ABC Fitness.

If you have a teen spending hours in the gym, you might be worried about their wellbeing. Is weightlifting healthy for teens, or should they wait until they are older? Should they be eating mountains of protein to build muscle? And what about that rumour that lifting too heavy, too young can stunt your growth?

We put these questions and more to Professor Craig Williams, a physiologist and director of the Children's Health and Exercise Research Centre at the University of Exeter.

Is it healthy for teenagers to weight lift/strength train?

One of the main benefits to teens weightlifting is the same benefit as for older weightlifters: hypertrophy, meaning the growth of muscle.

“If you stress the musculature of the human body by lifting weights that progressively get heavier over time, you will see an increase in the size of the actual muscle. Not only will someone know that they're stronger because they're able to lift heavier weights, but visually they will see that they are, too,” Williams says.

And the stronger you are, the easier any ‘work’ that you have to do will be, he says. “Because you’re now stronger, you’re more likely to have greater power — you can throw further or run faster,” he says. “Exercise is going to feel much, much easier, and you won’t be as affected by fatigue or stresses and strains.”

The strain that lifting weights puts on your muscles and tendons can actually be beneficial for bone health — and better bone health means higher bone density and a lower chance of fractures from osteoporosis, especially in older age.

Strength training can also help to decrease your risk of developing type 2 diabetes, improve your cholesterol, and generally improve your cardiovascular health.

A teenage girl is practicing weights for good posture in gym centre

Williams also points out that strength training, along with eating a well-balanced diet, can create healthy changes in body composition.

“As you continue to train, you might lose fat and see an increase in muscle mass. That is advantageous because we know generally it's better for the human body to carry more lean muscle than a lot of fat,” he says.

“Excess body fat can be inflammatory, which has some associations with cancers, and if you carry that excess body fat for a long period of time, that's going to have consequences on your joints and things,” he says.

In children specifically, excess body fat can affect puberty — obese children tend to mature faster and have more bone aging than their leaner counterparts.

Obese boys also tend to have lower testosterone levels, which can affect genital development, according to a 2021 study by researchers at the University of Milan. And a 2011 study published in the journal Reproduction found that obesity in pre-pubertal girls has been linked to higher chances of having polycystic ovary syndrome later in life.

How to know if they’re old enough

There isn’t one age at which children are ‘old enough’ to start weight training, Williams says.

“If the training programmes are correct and done appropriately, at the right age and sex and maturational status, all kids can benefit from a strength training programme,” he says.

However, it’s important to take their age and ‘maturational status’ into account, he says.

All children develop differently, and so two children of the same age won’t necessarily be at the same stage of physical development as each other — for example, if we take two thirteen-year-old boys, one could not have started puberty yet and have the ‘biological age’ of an 11-year-old, while the other could have put on much more muscle, started having surges in testosterone, and have the ‘biological age’ of a 15-year-old. These two boys shouldn’t, then, be doing the same training programme or lifting the same weights, because one is more advanced in his maturity

So, if you have a teenager who isn’t as far along in their adult development, they shouldn’t be training like a fully grown adult, or even their peers who perhaps have a few more beard hairs.

If we’re talking generally, Williams says that 15 is a good age to get started with weights.

“By 15, many youngsters growth is slowing down because they’re almost reaching their adult height,” he says. “So, 15 plus, in the right environment with good technical training on how to lift, is a good broad-brush age to start.”

Is it safe for teens to lift weights?

“The epidemiological studies on strength training have shown that it is, from an injury point of view, just as safe as any other sport for young people. In fact, they're probably slightly safer” if people have the right training, Williams says.

And the thought that lifting too heavy, too young can stunt growth?

“Yeah, that's a myth. If the training is done appropriately, if it's made relevant to the particular age, and particularly the biological age of the child, it’s safe,” he says. The study that fuelled this rumour was based on excessive weight training at a very young age, he says, which can “potentially damage the epithelial plates at the end of the long bones” — “but actually as soon as the weight training was done appropriately, at the right time and under supervised conditions, all the injuries went down.”

Young athlete exercising with barbell in gym

How much is too much? What’s appropriate?

There are general recommendations for what types of strength training is appropriate for different ages, Williams says.

“For example, for the ages of around 10 and 11, it’s not recommended to lift weights above your head. And then as you are going through your big growth spurts, which for boys is typically around 14 years of age, you can slowly increase the weight over time,” he says.

This is with the caveat that young people should have adequate rest and recovery time, and to make sure they aren’t increasing the weight that they are lifting too fast, so that their muscles aren’t over-trained.

“You shouldn’t change your training programme to increase the weights by more than 10% from one training period to the next,” Williams says. “This depends on how many repetitions you’re doing, too.”

He gives the example of barbell curls: if you can easily complete three sets of eight reps, you can increase the number of reps with the same weight — but not by more than 10%, so you might do three sets of 10 reps instead.

Teens should also be trained to lift weights correctly and be supervised.

“This also stops tomfoolery and messing around with the weights — most of weights accidents occur where the weight is dropped on somebody's foot or something,” he says.

How parents can support their teens in the gym

As Williams stresses, the most important way to support teens in the gym is to get them proper training, to avoid injury and make sure they aren’t damaging their bodies as they work out.

If your teen is going to a gym to work out, making sure that they are working with someone with the right qualifications and who understands that their needs are different from an adult’s is also key.

Another common training mistake is to believe that “more is better,” he says. But teens often miss out a key part of training: rest and recovery.

“It's important to have rest in between the sets when you're weight training, so you allow a bit of recovery of the muscles to be able to get ready for the next set. If you make that time period too short, then you'll just overload the muscles too quickly, and your ability to actually lift the weights will be compromised,” he says.

“That's a common mistake that many athletes make is thinking, ‘I don't need rest — if I'm resting, I'm not exercising. And if I'm not exercising, I'm not going to improve.’ When actually, the rest part allows the body to recover from the stress that you've imparted.”

This, combined with inadequate sleep and nutrition, can lead to ‘overtraining syndrome,’ where the body can’t cope with the amount of exercise it’s being pushed to do. Symptoms include anxiety, depression, and mood changes; fatigue and insomnia; unexpected weight loss or gain; and heart issues. Overtraining syndrome can take weeks or months to recover from — so it’s best to take enough time to rest!

Mom and daughter training together weightlifting

What should teens who lift weights be eating?

Teens usually need a little more protein than adults since they are growing. They need 0.8g per kilogram of bodyweight per day, as opposed to the 0.75g per kg of bodyweight that is recommended for adults.

Lots of people who lift weights will massively increase the amount of protein they eat in order to build muscle. But most often we don’t actually need to be eating as much protein as the shake companies and social media videos suggest.

If you’re looking to put on muscle, eating more protein can be helpful, as long as it’s no more than double the recommendation. But it’s important to note that any extra protein is just excreted out of the body via urine, so just because you’re eating more protein doesn’t mean you’ll automatically put on more muscle.

Creatine is a popular supplement taken by people who are looking to build muscle or increase exercise capabilities — but Williams says that it isn’t recommended for children and adolescents under 18. This is because we don’t know what the long-term effects are in young people, even though it’s considered safe for adults.

“You get creatine from your diet anyway, especially if you eat meat,” he says.

Almost 22% of young men report that they eat more or differently to build muscle, according to an article in the journal Current Opinion in Pediatrics, but Williams says that they probably don’t need to be doing that.

“You want a broad range of protein, carbohydrates, and fats. And you want to make sure that your plate is as colourful as possible and you’re getting enough vegetables and fruits. Stay hydrated with water and other fluids throughout the day, and you really don't really need anything over and above that,” he says.

Signs that it’s no longer healthy

Williams shared the following signs that a teen’s fitness routines are bordering on the unhealthy:

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Authors

Serafina Kenny journalist headshot

Serafina KennyDigital Journalist

Serafina Kenny is a Digital Journalist at MadeForMums. She writes news and features and has expertise in health, nutrition, relationships, and history. She has previously written for Business Insider, Women's Health, Stylist, Men's Health US, The i Paper, Dazed, and more. You can contact her with tips and story ideas (or compliments!) at serafina.kenny@immediate.co.uk.

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