Interview conducted by April Cashin-Garbutt, BA Hons (Cantab) on 26th July 2012
What defines obesity in children?
This is a very important question, primarily because we need to use one definition in order to be able to compare the prevalence of obesity in different countries. It is also important to have a single definition in order to evaluate whether interventions are successful or not.
The most widely used tool for defining obesity is the body mass index (BMI). For adults it is very clear what the cut offs are:
- Overweight is defined as a BMI between 25 and 30
- Obesity is defined as a BMI between 30 and 35
- Severe obesity is defined as a BMI above 35
Children have a different body composition and they are smaller and they grow. In 2000, the International Obesity Task Force, IOTF, developed cut off points for overweight (equivalent of adult BMI 25), obesity (BMI 30) and very recently new cut off points for severe obesity (BMI 35) (Cole BMJ 2000 and Cole and Lobstein 2012 Paediatric Obesity). This is the most used system.
The cut off points in children are age and gender specific and they are equivalent to the cut offs in adults.
How many children are affected by obesity?
This varies by country. The highest prevalence of obesity in children in Europe is around the Mediterranean. For example, in Greece and Spain 35 to 40% of 7-11 year old boys are overweight and around 12% are obese.
The statistics are very similar for the United States, where 35% are classed as overweight and 13% are classed as obese.
In other countries in Europe, particularly to the North and the East, the prevalence is lower. For example, in the Netherlands 14% of children are overweight and 2% are obese.
In the UK, the percentage of overweight boys is just above 25% and around 5% are obese.
What are the main causes of obesity in children?
I think many people know the two main reasons. Too much unhealthy food (like snacks with lots of carbohydrates and fat) and sodas containing a lot of sugar are bad for you. Also, too little physical exercise is bad for you, especially when in combination with too much unhealthy food.
The sad thing is that obesity is seen more often in low income and low educated families, so socio-economic factors play an important role as well.
Why do you think obesity in children is on the rise?
Although I think a lot of people by now know what they should do to prevent obesity, that is eat to healthy food and spend less time sedentary and exercise more and incorporate this healthy lifestyle into daily life; unfortunately, in daily practice it is quite difficult to change your lifestyle.
How much should we blame the increase of “junk food” for the obesity epidemic in children?
That is difficult to answer. There is a clear link between junk food and the obesity epidemic, but this is only one factor as there are a lot of risk factors for obesity.
Sedentary life is an important one in childhood, spending hours and hours passively watching television and munching high calorie snacks is important too.
But, if we want children to move around more they need access to places in the neighborhood where children can play outside, run around, or play tag or soccer. We should also encourage children to walk or cycle to school instead of taking the bus.
How much should we blame the increasing popularity of video games for the obesity epidemic in children?
A sedentary life, such as watching lots of television, is a very important risk factor for obesity. But, watching television may be even worse than playing video games. This is probably because while playing video games children tend to move a little bit. This makes it a little less passive past time.
Why is obesity in children such a problem?
There are short term problems like bullying and depression but also there are very nasty long term effects and complications such as hypertension, cardiovascular disease, fatty liver disease and diabetes. There is a long list of complications that stem from being obese.
Your recent research reported that two out of three severely obese children have at least one risk factor for heart disease. What types of risk factor did your research find?
That is correct - two thirds of severely obese children, even young children, have cardiovascular risk factors. This should really be none.
The most predominant risk factor we found was hypertension: more than half of the severely obese children had hypertension. In the normal population this would be less than a few percent. The striking thing was that this also applied to really young children under 12 years of age.
Furthermore, half of the severely obese children have abnormal lipids like high cholesterol and 14% has high blood glucose which is a precursor of diabetes
Please could you tell us a little bit about heart disease and who does it normally affect?
Heart disease normally affects middle aged age and older people. However, and this is what we as pediatricians find really shocking, young children that are severely obese already have risk factors for heart disease like hypertension and high cholesterol.
We know that hypertension leads to atherosclerosis, which in turn leads to heart, kidney disease and cerebrovascular disease.
At what age would you expect an obese child to develop heart disease?
That is a difficult question to answer and it will also depend on the condition of these severely obese children later in life: if they become normal weight, the risk for cardiovascular disease will probably subside; however, if they continue to be obese as adults, they may well develop heart disease, kidney disease and diabetes at an early age.
How do you see the future of obesity in children progressing?
The obesity epidemic is still progressing. In the Netherlands, the last growth study was in 2009. In this they found that 14% of children were overweight. The last study before that was in 1980, when they found that it was only 9 or 10%.
We need a community based effort involving everyone to stop the obesity epidemic. We need local government to supply enough playgrounds and green space for children to play and exercise.
We need the food industry and local supermarkets to promote healthy snacks and drinks for children.
We also need the school to provide healthy fruit and vegetable lunches in the school canteens and to educate children in healthy food choices and exercise. And most importantly we need to involve parents in providing a healthy lifestyle environment for their children.
How do you see the future of heart disease progressing?
I am afraid that obese children, if they continue to be obese, will have cardiovascular disease at an early age, much earlier than the generation of their parents.
But it is not only heart disease that we are afraid of but also kidney disease, liver disease, cerebrovascular disease and diabetes. Already pediatricians see more and more children with type 2 diabetes because of obesity. This did not occur 10 or 20 years ago.
Are there plans in place to cope with the number of children who will eventually develop heart disease in the future?
That is a good question. I think it will be necessary for the medical profession to plan ahead because more people, at younger age, will have cardiovascular disease and diabetes because of the obesity epidemic.
Do you have any plans for further research into this area?
We are planning to study the impact of measurement (on a regular basis) of blood pressure and treatment of hypertension in overweight and obese children. We are hoping to look at how this correlates with their BMI and the condition of their blood vessels.
We hope finding hypertension in obese children will be a wake-up call for parents and children and will help them to actually make a change to a healthier lifestyle.
Where can readers find more information?
They can read our paper here: http://adc.bmj.com/content/early/2012/07/12/archdischild-2012-301877
They can find out more about the EMGO - institute and VU University Medical Center in Amsterdam, the Netherlands, here: www.emgo.nl
About Joana Kist-van Holthe
Joana Kist-van Holthe, MD PhD is a pediatrician with a passion for research. After 25 years clinical experience as all round pediatrician and as pediatric nephrologist, she decided it was time to change her career and spend more time on research. Her primary interest is Childhood Public Health.
In 2010 she started to work with Remy HiraSing, Professor Youth Care at the department of Public and Occupational Health, EMGO Institute - VU University Medical Center in Amsterdam, the Netherlands (www.emgo.nl).
Currently she participates in research mainly pertaining to childhood obesity. She is also involved in the development of a guideline for prevention and treatment of overweight and a guideline for children with food allergies in Child Health Care in the Netherlands.
For more information on Joana please visit: www.emgo.nl/team/1310/joanakist-van%20holthe%20tot%20echten/personal-information/
The relationship between calcium consumption at various times of the day and cardiovascular disease