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Children constantly change – in size, eating habits and physical abilities. Height and weight gains can reassure parents that a child is healthy and has enough to eat. It can be very challenging to know how much weight gain in childhood and adolescence is too much! Thankfully, there are tools that help tell the difference between a child growing normally and one whose weight indicates a risk of health problems.
One such tool is the body mass index (BMI). The BMI compares the weight and height of an individual child, and is calculated as follows:
| BMI = | weight(kg) |
| height (m)2 |
Once the BMI is calculated, it can be plotted on a BMI growth chart. As with familiar weight and height charts, the chart provides a BMI percentile. The growth of the individual child can be compared to the range of normal BMI for that age group. For instance, a BMI at the fifth percentile indicates only five per cent of children have a BMI less than that value. A BMI at the 85th percentile indicates that 85 per cent of children have a lower BMI.
Children growing normally tend to stay on a similar percentile line throughout childhood. In general, values between the fifth and 85th percentiles are considered to be within the normal range. When a BMI value is between the 85th and 95th percentiles, the child is at risk of being overweight. A value above the 95th percentile indicates too much weight. If a BMI percentile continually moves upward, that child’s eating and physical activity habits may lead to excess weight even if the range is below the 85th percentile.
Using the BMI as a guide, we can compare children from the last several decades to today’s children.
The graph here shows the percentage of children at risk of excess weight (with a BMI in the 85th to 95th percentile) and overweight (greater than 95th percentile). Over a 30-year period, the at-risk group rose from about 15 to about 23 per cent, while the overweight group rose from five to 10 per cent. In 2004, 30 to 40 per cent of children are estimated to be at risk while 15 per cent are overweight. This is a significant increase from 1991. While it took over 30 years for the rate of overweight to double from five to ten percent, the increase from 10 to 15 per cent took less than 15 years. This data leaves no doubt that the number of overweight children is increasing quickly!
For anyone, adult or child, weight is the result of an energy balance equation:
Calories |
- |
Calories |
= |
Body |
In |
Out |
Weight |
All of our calorie intake comes from food and can be changed by eating more or less. Calorie output maintains body functions including breathing, digesting food, growth, and physical activity. Since calorie output needed for body functions and growth remains fairly constant, the only way to change energy output is by changing physical activity.
Modern society has had a major impact on both the amount we are eating and the physical activity we do. High-calorie foods are readily available, convenient and fairly inexpensive. We are able to live comfortably without doing as much. TV, computers and other inactive pursuits have replaced leisure-time physical activity. The result is a society of adults and children who are gaining too much weight.
Yes, excess weight affects children in many ways. Diseases previously seen only in adults are showing up in astonishing numbers in our children.
Heart disease: Overweight children are more at risk of coronary (heart) artery disease that can lead to heart attacks. High blood pressure is 2.4 to seven times more common among overweight children, while high cholesterol levels are three times more common. A study was done of overweight adolescent boys (15 to 19 years) who died of causes not related to being overweight. It showed that some had developed advanced coronary artery disease before reaching their 20th birthday.
Diabetes: In 1982, only four per cent of children newly diagnosed with diabetes had type 2 diabetes. This type develops with excess weight as the body becomes resistant to its own insulin. Today, some clinics have found that up to 45 per cent of kids newly diagnosed with diabetes have type 2 diabetes; many of these boys and girls are overweight. Overweight children have a high risk of developing the insulin resistance that can lead to diabetes. The risk can be 12.5 times more than that of a normal-weight child.
Sleep apnea: Sleep apnea, where breathing stops during sleep due to obstruction of the airways, may occur in 25 to 30 per cent of overweight children. It can lead to physical problems as well as difficulty with behaviour and school due to lack of sleep.
Bone problems: The bones and joints of an overweight child undergo extra stress and wear. Several bone and joint problems happen only (or much more frequently) in overweight children.
Liver disease: In recent years, a condition known as non-alcoholic steatohepatitis (NASH) has been recognized among overweight people. In NASH, an accumulation of fat leads to inflammation in the liver. This uncommon problem has been increasingly seen in overweight children, and can lead to permanent liver damage.
Quality of life: Convincing evidence shows that overweight kids feel that they have a poorer quality of life compared to their peers of normal weight. If the child has medical complications, the difference is even greater.
The solution begins at home. Diet and physical activity are key to body weight, and patterns of eating and activity are usually established within in the family. Since many overweight children have at least one overweight parent, developing a healthier lifestyle is good for everyone in the family!
Canada’s Food Guide to Healthy Eating (www.hc-sc.gc.ca/hpfb-dgpsa/onppbppn/food_guide_
rainbow_e.html) is an excellent tool to help on the road to healthier eating. Since eating habits are established over a lifetime, be patient in making changes. Making a small change that becomes a permanent habit is more valuable than a complete dietary overhaul that only lasts a week. Look for ways to make change easier, such as planning meals and buying and preparing foods ahead of time. Work together as a family. Here are a few ways to work toward healthier eating.
Increase fruits and vegetables. Most people – adults and children alike – don’t consistently meet the recommendations for this food group. Rather than focusing on what you or your child can’t eat, try to increase the amount of fruits and vegetables.
Check on dairy. As children get older, dairy intake often decreases. It is the most important source of calcium in the diet, so growing children should eat (but not exceed) the recommended intake. This may be another area where intake can be increased.
Check portion sizes. The food guide shows the amount of food that counts as a portion. It is often much less than you think! It is easy to underestimate how many portions you are eating unless you actually measure, especially with the grains food group.
Dine in. It can be hard to make healthy choices when dining out. Food prepared at home is often healthier and served in more reasonable portions than restaurant fare.
Treats – what to do? Most of us enjoy a special treat now and then. High-calorie treats tend to be low in nutrients and often take the place of healthier foods. Start by gradually decreasing the size and frequency of treats. Consider replacing food treats with rewarding or special activities.
Everyone thinks that kids are always on the go – and for some this is true. However, many kids spend free time watching TV or playing video games, often for hours at a time. Increasing physical activity also requires a gradual approach.
Decrease screen time. The Canadian Pediatric Society recommends that kids spend no more than two hours a day watching TV or playing a video game. Gradually reducing the time spent at these activities will not decrease weight on its own, but it will give kids a chance to become more active.
Make it fun. A child who is bored walking on a treadmill or pedalling a stationary bike will stick with activities that are fun. Although organized sports activities are one option, a short but intense game of tag can have the same effect as a soccer game spent mostly on the sidelines.
Be a role model. Your kids take their cues from you. By concentrating on getting more active, you send a powerful message about the value of physical activity. Do it together and cheer each other on. It is not easy to change habits. Let your child support you as much as you support your child. Any challenge is more manageable when you face it together.
Habits usually develop because they make a situation easier. It is worth looking not only at what you do about diet and physical activity, but also why you do things that way. Finding a way to make healthy choices easy will increase your chances of success. Each new healthy habit is a success in itself and should be celebrated! The reward is a lifetime of good health for you and your child.
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