Body mass index (BMI) in children

Body mass indices and weight curves for children and adolescents

When calculating BMI for children and young people, the effects of age and gender must be taken into account. “Estonian Nutrition and Exercise Recommendations” The appendixes of the publication contain growth curves for height and weight of children of different ages, compiled by Estonian pediatricians. Although it is most appropriate to base the assessment of normal weight of children on the weight curves compiled by Estonian pediatricians, graphs of children's body mass indices according to age and gender have also been compiled.

What are the normal values for body mass index in children and young people?

In children and young people, the same values as in adults cannot be used to assess body mass index. When assessing a child's weight based on body mass index values, the growth stages of children, which affect body composition and proportions, as well as individual differences and development, must be taken into account. It is important to assess the weight dynamics or average weight gain of growing children: from the age of 3 to puberty, it is 2 kg per year and for 11–14 year olds, it is 5–6 kg per year. Stagnation in weight or greater than average weight gain requires attention and identification of the causes.

Considering the above, the World Health Organization has created separate body mass index charts. for girls and for boysIn addition, the Sports Medicine and Rehabilitation Clinic of the Tartu University Hospital has prepared a simplified children's body mass index table, where you can see the underweight and overweight values according to age:

Child's age (years)	BMI indicating overweight	BMI indicating underweight
7-9	>19	<14
10-12	>22	<15
13-15	>24	<16
16-18	>25	<17

 

What other tools are used to assess a child's weight?

In addition to body mass index and weight curves prepared by pediatricians, additional tools are used to assess underweight, normal weight, and overweight in children aged 2–18, such as measuring skinfold thickness and administering questionnaires if necessary. If a child's weight, body image, and daily eating habits may indicate an eating disorder, the following questionnaires are used:

• from the age of 15, the emotional well-being questionnaire and the eating disorder assessment scale are used to assess emotional state;
• The Children's Eating Attitudes Scale is used for children aged 8–14.

 

Body mass index (BMI) studies among Estonian children

Most studies only cover a few age groups and are based on students' self-reported weight and height, making it difficult to say exactly how many Estonian children are obese or overweight. However, it is clear that the number of overweight children and young people has been increasing over time.

Estonian School Children Health Behavior Survey (HBSC) is part of an international study and one part also addresses the topic of nutrition, exercise and weight. The study interviews students in grades 5, 7 and 9, or generally children aged 11, 13 and 15. According to the results of this study in 2021/2022, 15% of girls and 25% of boys are overweight or obese. The number of young people with excess weight has increased among both girls and boys, but the biggest change is among boys.

Estonian Student Growth Survey (COSI) is an initiative of the WHO Regional Office for Europe and is conducted among 6-9 year olds. The results of this survey in 2018/2019 revealed:

• the proportion of overweight students increases with age;
• In the first grade, every fourth student is overweight;
• in the fourth grade, every third student is already overweight;
• In fourth grade, there are twice as many obese boys (16%) as girls (8%).

According to various studies, the prevalence of anorexia is 0.5-3.7% and the prevalence of bulimia is 1.1-4.2%. Anorexia and bulimia are among the most common mental health problems among adolescents.

Calculating BMI for children and its importance

Calculating a child's body mass index according to age and gender is a simple and useful way to assess underweight or overweight. However, if possible, it is worth using the growth and weight curves compiled by pediatricians in Estonia as a basis for assessing a child's weight. It is also worth remembering that it is not possible to assess a child's health status comprehensively by assessing a child's weight alone. If health risks are suspected, additional examinations are possible and necessary.

A healthy and balanced diet and adequate exercise help children maintain a normal weight. Avoiding overweight or underweight and getting enough energy and nutrients results in:

• many diseases can be prevented;
• good feeling and mood;
• better thinking ability, which also has a positive effect on academic and work performance.

Problems related to obesity

A body weight significantly different from normal weight is also a health risk for children. 

Overweight and obesity are associated with several health risks and comorbidities, including:

• Type 2 diabetes, 
• insulin resistance, 
• dyslipidemia, 
• metabolic syndrome, 
• cardiovascular diseases, 
• respiratory diseases (including asthma, sleep apnea), 
• osteoarthritis, 
• some malignant tumors (e.g. digestive system tumors, endometrial, cervical or ovarian cancer in women, breast cancer after menopause, prostate cancer in men), 
• digestive system diseases (gallbladder, pancreas, gastroesophageal reflux), 
• urinary and genital tract disorders (chronic kidney disease, kidney stones, stress incontinence, infertility problems, menstrual cycle disorders in women).

Childhood obesity is linked to also:

• with psychological problems such as anxiety and depression;
• with low self-esteem and quality of life;
• social problems such as bullying and stigma;
• overweight as an adult.

Problems related to being underweight

In children and young people, it is important to be especially vigilant to notice unusual changes in the child's weight and investigate whether there is cause for concern. In addition to excess weight, serious eating disorders are increasingly common. Eating disorders are illnesses in which the perception of one's own body and daily eating are severely disrupted.Eating disorders include:

1. anorexia;
2. bulimia;
3. malnutrition;
4. overeating;
5. orthorexia.

When it comes to children and young people, one must be attentive and take a holistic approach, taking into account all areas of life. It is good to support in a patient, informed, compassionate, encouraging, non-judgmental and realistic way.It is important to emphasize positive body image and encourage children and young people to focus on health, not just their weight. Self-love and confidence should be promoted and they should be taught to appreciate the versatility and capabilities of their bodies.

How to achieve a normal body weight and a healthy body mass index in children?

The physical activity and eating habits of the whole family have a significant impact on the achievement of a normal weight in children and young people. The smaller the child, the easier it is to influence their eating habits. For example, adolescence is a period of high nutritional risk, because although the need for nutrients increases, poor food choices, unhealthy eating habits, and deficiencies of energy and proteins and many vitamins and minerals may occur. It is difficult to influence teenagers towards a healthier diet. However, it is possible to guide them indirectly: by the food choices offered, by your own example, by increasing or reducing the availability of certain foods.

The Estonian Institute for Health Development has compiled an exercise pyramid, which outlines the main recommendations to follow when developing physical activity habits. It is important to reduce sedentary activities, be as mobile as possible, and find enough time for aerobic activities and stretching, balance, and strength exercises.

In addition to an active lifestyle, it is important to pay attention to your dietary habits. Evidence-based recommendations are in the guide. "Estonian Nutrition and Physical Activity Recommendations 2015". 

General dietary recommendations are also given In the food pyramid created by the Estonian Institute for Health Development. It has also been created sugar calculator, which allows you to find out how much sugar we actually consume. In addition to the body mass index calculator, the Nutridata website also energy recommendation calculatorIn addition to calculators, Nutridata's free nutrition program allows you to keep a food and exercise diary, analyze eating habits, and test sample menus.

In addition to such general information materials, it is also possible to find information specifically aimed at children and young people. Several publications have been prepared specifically for children and young people. In print “Nutritional recommendations for children and young people” Nutrition recommendations for children and young people aged 3-18 are introduced. Print “Nutrition and food recommendations for young people” The goal is to help young people aged 18-26 make healthier choices, taking into account financial constraints and limited opportunities.

From the information portal tarkvanem.ee, created for parents You can find nutritional recommendations by age group. A portal has been created for children and young people Fiidi Bear, where examples of meal choices are shared in a simple and playful way, you can test your knowledge of myths and nutritional recommendations during the game, and watch videos on the topic.