The Obesity Epidemic and its impact on Young New Zealanders' Lives

Professor Ed Mitchell

Chair of Child Health

University of Auckland

Background to Research

The recent obesity epidemic in New Zealand is not only affecting adults but also young children and threatening to cut short their lives.  Children and adolescents who are overweight or obese are frequently obese as adults.  Obesity is strongly linked to a number of common medical disorders including metabolic syndrome, type 2 diabetes, hypertension, obstructive sleep apnoea and coronary artery disease.  Infants born small, especially those showing excessive catch-up growth, are also at increased risk of obesity and cardiovascular disease as adults.

What are your research objectives?

A number of studies have identified a significant connection between obesity and hours of television watching and lack of physical exercise.  However, these studies are predominantly cross-sectional surveys and few have made objective studies of physical activity.  There is also little in the way of prospective studies of activity and body fat change during childhood.

Dietary factors are thought to be important in the development of obesity.  An association between the consumption of sugar sweetened drinks and childhood obesity was reported in a prospective study but this again needs further study.  It is clear that children who eat fast foods consume more total energy, fat, carbohydrate and sugar than those who eat fast food infrequently.  But we need to know more.

Therefore the major aim of this project is to study 11-year-olds and identify risk factors, including cardiovascular risks, for being overweight or obese.  We want to see how they differ for infants born small for gestational age (SGA) and those born appropriate for gestational age (AGA).

The information from this study will obviously improve obesity prevention programmes.

How will you conduct your research?

This research is the 5th phase of the Auckland Birthweight Collaborative study which has focused on collecting data from a group of Auckland children for the past 11 years.  Half the children involved in the study were born small and half were normal size.  Data have been collected at birth then at one, three, five and seven years of age.  At seven years physical activity was objectively assessed using a movement monitor (accelerometer), as were behaviours such as television watching and diet.

The current study will assess the same children at 11 years of age. We will measure diet, physical activity, vigorous activity, sedentary behaviour and fitness and examine how these factors and patterns of growth affect weight and other cardiovascular risk factors.

Are there others in your field in NZ or globally conducting similar research?

There have been other cross-sectional studies which provide clues about the links between such things as television watching and obesity.  But these studies do not tell the whole story, e.g. does television watching cause obesity or do obese children watch more television because they are less mobile?  Our study aims to show whether lack of physical activity leads to obesity or is a consequence of the disease.

What is innovative about the approach you are taking?

There are some international longitudinal studies that are examining obesity, but none have the extensive range of objective measures that we have collected.  Our study is vitally important because it will highlight the risks for overweight and obese children and hopefully steps can be taken to reverse the problem and improve their quality of life

If you achieve your objectives what will that mean to those suffering from the disease or to the knowledge advancement of this disease?

While data gathered in this project will identify risk factors for overweight or obese children and adolescents, it also has the potential to identify intervention and prevention strategies.  This means we can not only address the problems for children already at risk of poor health if they are overweight or obese, but also ensure those with good exercise and nutrition habits maintain them.  This will lead to excellent health promotion and education strategies which will have beneficial spin offs for all children, not just those involved in our study.

Is there national or international collaboration on your research project?

There is no collaboration on this study.

The FLAME Study (Family, Lifestyle, Activity, Movement, and Eating)

Indentifying Risk Factors in Obesity

Professor Barry Taylor

Department of Women’s and Children’s Health

University of Otago

Background to Research

The annual cost of obesity to the New Zealand healthcare system was estimated at $135 million in 1996, but conservatively excludes the downstream cost of chronic disease resulting from obesity.  Diabetes and coronary heart disease alone could increase the financial burden by as much as $747 million/year.

New Zealand has been inadequately prepared for the worldwide epidemic in obesity.  Worldwide, 22 million children under the age of five are estimated to be overweight.  Obesity is increasing in prevalence, becoming established earlier in life and overweight children are becoming heavier.  In New Zealand in 2002, a disturbing 27% of five to six- year-olds were identified as overweight or obese.  Using growth charts recently published by the World Health Organisation, we found that in 2004, an alarming 50% of our sample of Dunedin three-year-olds were overweight or obese.

Without prevention or early intervention, overweight children carry with them into adulthood, adverse risk for cardiovascular disease, hypertension, stroke, type 2 diabetes, certain forms of cancer, and psychosocial problems.  There is also now good evidence that an overweight child who becomes an overweight adult, has a much greater risk of cardiovascular problems than someone who becomes overweight during adulthood.

What are your research objectives?

We are following 240 families with three-year-old children, over a four-year period until their children turn seven, to determine which family lifestyle factors, related to physical activity, sedentary behaviour and eating habits predict childhood obesity.  By identifying associations between the development of obesity and behaviour in the preceding pre-school years, the FLAME study will have implications for a time in life when intervention may still have preventative potential.

How will you conduct your research?

Since 2004, our sample of 240 three-year-olds have been receiving six-monthly measurements of height, weight, waist circumference, and body composition (fat and lean tissue mass) using a simple bioelectrical test.  From these measures we derive estimates of the children’s body composition, which are validated at age five by an x-ray scan (DXA scan).

Children’s dietary intakes and families’ eating habits are annually assessed by questionnaire and by three-day food diaries which record each child’s intake of specific foods, food groups, and beverages relevant to obesity.  Parents’ control and concern regarding their child’s diet, the structure of family meal times, and the frequencies of missed meals, TV meals, and takeaways are also assessed by questionnaire.

A unique feature of our study is the use of a recent technological innovation to provide objective measures of physical activity.  The accelerometer is a small unobtrusive device, which measures movement in three dimensions.  Parents and children in our study wear a waist-mounted accelerometer for seven consecutive days and repeat measures are obtained from children once a year.

Are there others in your field in NZ or globally conducting similar research?

Although a considerable amount of research is being conducted to address the worldwide problem of obesity, few longitudinal studies have investigated obesity- promoting family lifestyle factors in the pre-school age group.

What is innovative about the approach you are taking?

The FLAME study offers a unique contribution to existing research for the following reasons:

Following children over a four year period, rather than taking a cross-sectional snapshot at a particular age, identifies specific lifestyles that are more likely to be the causal determinants of children’s obesity.

Obtaining information from both parents and child provides a comprehensive assessment of obesity-promoting lifestyles within the whole family environment.

Investigating the pre-school and early childhood years focuses on an important, but previously under-researched period in the development of childhood obesity.  Since the weight status of a child, as young as seven years, is a reliable predictor of their weight status as an adult, an effective prevention strategy needs to be founded on age-appropriate research.

Using the accelerometer to provide an unambiguous, objective measure of physical activity will help clarify the subjective, often proxy-reports of physical activity that previous studies have derived from questionnaires.

If you achieve your objectives what will that mean to those suffering from the disease or to the knowledge advancement of this disease?

The development of an obesity-prevention strategy will clearly benefit from knowing the obesity-promoting family lifestyles of contemporary pre-schoolers.  From the outcome of the FLAME Study, we will be able to identify pre-schoolers who are at risk of becoming overweight, and we will have important implications for interventions designed to alter their growth trajectory.

Is there national or international collaboration on your research project?

A precise measure of children’s percentage body fat has been obtained by x-ray scan (DXA-scan) in conjunction with Professor Ailsa Goulding (University of Otago, Dunedin).  Dr Leigh Ward (University of Queensland) has extensive experience with the bioelectrical test we use to measure body composition and will assist in validating this procedure with our three to seven year-old children.