Growth and weight changes in teenagers

The move from child to adult triggers a significant growth spurt, and the average teenager may eat large amounts of food as their body builds bone and muscle. There are several ways to assess this growth.

Peer pressure and media images can influence how your child relates to food. Eating problems, such as overeating (which may lead to obesity) or crash dieting (which may lead to being underweight), can develop during the teenage years.

Parents are still the main role model#

Despite what many parents think, even the most defiant teenagers still look to their parents for guidance. Parents remain a teenager’s main role model, even alongside the powerful influence of peers and the media. If you encourage healthy eating habits for the whole family, your teenage children are likely to follow your example.

The way you respond to your child’s body image concerns can shape their attitudes and behaviors. Suggestions include:

• Be a good role model and don’t crash diet or skip meals.
• Educate your child about the pitfalls of unhealthy eating habits, but don’t react harshly against their choices.
• Respect that teenagers like to experiment with food. For example, some may want to try being vegetarian. Try to respect the choice and help them plan a vegetarian diet that includes all the essential nutrients.
• Boost your child’s self-esteem. Encourage physical activities that help them appreciate what their body can do, rather than what it looks like. Studies show that high self-esteem can protect a teenager against harmful behaviors such as crash dieting.
• Educate your child about the persuasive methods used in advertising and marketing, and encourage them to learn about health issues and take responsibility for their own attitudes and behaviors.

A stubborn teenager may dismiss your advice about nutrition, but they may respond with more enthusiasm if you give them access to independent and reliable sources such as your doctor or a dietitian.

Don’t assume that your child is eating less because they are trying to lose weight. The end of a growth spurt often triggers a drop in appetite.

How growth is measured#

Doctors, nurses and other health professionals use a variety of methods to assess growth in teenagers, sometimes using one approach and sometimes a combination. The most common include:

• Growth charts. Standard growth references or growth charts help interpret a teenager’s height and weight measurements. They are drawn from population studies and reflect the normal range of height and weight from birth up to adulthood.
• Body mass index (BMI). Age-specific BMI percentile charts give an indication of the weight-for-height ratio.
• Body composition analysis. The “skin fold test”, for example, gently pinches the skin with callipers (a two-pronged measuring tool) to assess the amount of fat below the skin. Underwater weighing is a more accurate body composition test, but it is expensive and mainly used for research.

Understanding BMI#

The body mass index (BMI) is the most common way to assess whether a person is underweight, a healthy weight or overweight. It is a single number that interprets a person’s weight in relation to their height, calculated by dividing weight in kilograms by height in meters, squared.

BMI percentile charts are available for children over the age of two to assess weight and obesity. The charts use percentile cut-offs as a guide only:

• The 85th percentile and above indicates a child is overweight.
• The 95th percentile and above indicates obesity.

As children grow, their amount of body fat changes and so does their BMI. That is why a BMI calculation for a teenager must be compared against growth charts that are appropriate for their age.

When to seek advice#

Always see your doctor if you are concerned about your child’s growth. Your doctor can use a range of charts to help assess whether your child’s growth is a cause for concern.

Puberty can have a major impact on growth. Because puberty can begin any time between the ages of nine and 13 years in girls, and 11 and 15 years in boys, assessing a teenager’s development can be more complicated. For this reason, it is a good idea to seek professional advice if you are concerned.

Key points#

• Parents remain a teenager’s main role model, even alongside the powerful influence of peers and the media.
• Respect your child’s food choices, such as choosing to be vegetarian, and help them plan a balanced diet with all the essential nutrients.
• Don’t assume your child is eating less to lose weight, as appetite often drops at the end of a growth spurt.
• BMI is the most common way to assess whether a person is underweight, a healthy weight or overweight, but for teenagers it must be compared against age-appropriate growth charts.

Where to get help#