Key Findings from Earlybird

In Summary

• Obese children – parents unaware and unconcerned. Today’s parents are oblivious of their children’s weight
Parents are key partners in the drive to halt obesity, but will have
little impact unless educated to recognise the problem

• Children’s activity not determined by environmental opportunity Green spaces and sports centres do not influence the physical activity of children
Like most things biological, a child’s activity level seems to be ‘set’
by the brain, and therefore strongly defended against change

• Social inequalities no longer a major factor in obesity. All children today are at risk, regardless of family income or postcode
Targeting by SES unlikely to be effective

• Obesity leads to inactivity, rather than the other way round. Time-lag analysis from one year to the next suggests obesity comes first
Crucially important - calorie reduction, rather than physical
activity, appears to the key to weight reduction

• Healthy weight for life? Start at birth. Most excess weight (90% in girls) is gained before the child ever starts school
School initiatives are probably too late. Mums should be
encouraged not to overfeed low birth weight babies, who are
most at risk of later weight gain

• Average child no heavier than 25 years ago. The rise in obesity is confined to a small group of children who are behaving differently from the majority who have not changed in a generation
There may be no widespread childhood obesity epidemic

• Obese parents – in particular those of the same gender – key to childhood obesity. It is well known that obese children take after their parents, but the current rise in childhood obesity appears linked specifically to the parent of the same gender - obese mothers are breeding obese girls and obese fathers obese boys
It may be more profitable to target the obese parent than the
obese child

• Girls at greater risk of type 2 diabetes than boys. Girls are intrinsically more insulin resistant than boys, which could explain why more girls get type 2 diabetes in childhood
Scarce resources might be better targeted at girls

• Type 1 and Type 2 diabetes essentially the same disorder of insulin resistance, differing only in tempo.
Keeping weight down should help prevent, or at least delay, the
onset of both type 1 and type 2 diabetes

In Detail

EarlyBird is a focused cohort study, monitoring the causes and behaviour of insulin resistance in contemporary children. Insulin resistance, largely the result of obesity, is believed to underpin the development of diabetes and cardiovascular disease that characterise modern society.
EarlyBird is distinctive in combining objective measures of physical activity and body composition from the age of 5y with annual fasting blood samples, which reach beyond simple body composition (BMI and body fat) to metabolic health (insulin sensitivity, blood fats, cholesterol, blood pressure).
The study is generating some novel and sometimes counter-intuitive findings, which have nevertheless withstood the rigours of peer review - over 50 papers are now in print. It has already accumulated nine annual data sets, and retains almost 80% of the original cohort. It is intended that the study continue until the youngsters reach 16 yrs of age.

Timing the Onset of Obesity

• Obesity starts early: All children gain weight during growth, but EarlyBird is interested in the excess gained. There is much concern about school meals, PE time, after-school clubs, television viewing, computer games and green space in the cause of childhood obesity - all of them primary school issues. However, EarlyBird finds that over 90% of the excess weight in girls, and over 70% in boys, is gained before the child ever gets to school age. These findings support a need to re-direct public health initiatives towards an earlier period in childhood. (Gardner DS-L - Pediatrics, 2008).

The Obesogenic Environment

• There is no longer an association between low birth weight and later diabetes: Diabetes risk in contemporary children lies with excess weight gained in early childhood and yet parents are still encouraged to feed up low birth weight babies. This raises an important public health issue - the importance of keeping weight gain low in children of low birth weight (Wilkin TJ -Diabetes 2003).

• Obese children - parents unaware and unconcerned: Overweight is now perceived as the norm and today's parents are no longer aware of their own or their children's weight. This report hit the world's media, because it revealed a serious issue for the campaign to reduce childhood obesity. Parents are essential partners in the struggle yet, crucially, they do not acknowledge the problem. (Jeffery AJ - BMJ 2005).

• Social inequality is not associated with physical inactivity: Despite clear evidence of a socio-economic gradient in sports club attendance among the children, EarlyBird can find no evidence for corresponding differences in physical activity. The assumption that children of lower socio-economic status suffer from their lack of structured opportunity for physical activity is not reflected in the evidence. Indeed, analysis suggests that poorer boys may be marginally more, rather than less, active than those who are wealthier. (Voss LD - Child Care, Health and Development 2008).

• Obesity leads to inactivity, rather than inactivity to obesity: Using time-lagged correlation to imply direction of causality, weight gain appears to lead to (precede) inactivity, rather than inactivity to weight gain. Crucially important – it suggests that calorie reduction, rather than increased physical activity, may be key to weight reduction (European Congress on Obesity Amsterdam May 2009).

• Obese parents – in particular those of the same gender - have become a major contributory factor to childhood obesity: The average UK child is no heavier today than he/she was in 1990. The mean BMI has certainly risen, but the median hasn't changed. The "new fat" of the childhood obesity epidemic appears restricted to a subgroup of children - those whose same-sex parents are overweight or obese. Gender assortment of this kind suggests role-modelling. (Perez-Pastor E - International Journal of Obesity 2009)

Physical Activity/the Activitystat Hypothesis

• Children who keep active are no lighter, but they are metabolically healthier: The UK and US Governments advise at least 60 minutes moderate physical activity every day. Only 42% of the EarlyBird boys and 11% of the girls met this guideline consistently over the three-year period from 5-8yr. Importantly (because governments use BMI as their outcome measure), there were no differences in the trend for BMI over the four time points in either sex, but the more active children became metabolically healthier. The study questions the utility of BMI as the outcome measure of physical activity programmes in children and also whether the bar for girls should be lowered (girls systematically record less physical activity than boys). (Metcalf BS - Arch Dis Child 2008).

• Children's activity is not determined by provision: Those who do less in school do more out of school, and end up the same. Less than 1% of the four-fold variation in physical activity among children can be explained by the five-fold variation in PE provided at school. The report was based on a single school term (Mallam KM - BMJ 2003), but we have recently extended the analysis to four consecutive school terms. The result was the same and we question Government policy of expanding recreational facilities in an attempt to make children more active. (Fremeaux AE, 2010)

• Being driven to school may not be eco-friendly, but it does not reduce a child's overall activity: he/she makes up for it elsewhere in the day. The activity cost at the age of seven of being driven to and from school during the hours 8-9am and 3-4pm is 16%, but overall nil. (<0.1%). As in the schools study, those who lack the opportunity for physical activity at one period of the day appear to compensate for this at another. (Metcalf BS – BMJ, 2004)

• EarlyBird's Activitystat Hypothesis proposes that a child's activity is regulated by the brain, rather than the environment: The evidence we are accumulating suggests the activity of children is "programmed" - either genetically or as a result of very early experience. There is little evidence from EarlyBird studies that more or better recreational facilities/opportunity are associated with more activity in free-living children. (Wilkin TJ – Int. J Obesity 2006).

Genes and the Gender Insulin Hypothesis

• Girls are at greater risk of type 2 diabetes than boys: Girls are intrinsically some 35% less sensitive to insulin than boys and childhood type 2 diabetes is much commoner in girls. Young overweight females may be more important to target than males (Murphy MJ - Pediatrics 2004).

• Girls are born lighter than boys: a finding that is universal throughout the human race. Birth weight is mostly related to growth during the third trimester of gestation and this, in turn, to levels of foetal insulin. The hypothesis proposes that the greater insulin resistance which renders females more susceptible to diabetes may also be responsible for their lower birth weight. Finding the sex-linked gene responsible could unlock a mechanism that controls insulin resistance, the basis for type 2 diabetes. (Wilkin TJ - Int J Obesity 2006).

The Accelerator Hypothesis

• Type 1 and type 2 diabetes are the same disorder of insulin resistance and differ only by tempo, largely determined by different genetic backgrounds: The incidence of type 1 diabetes is rising as fast as type 2, and both are rising in parallel with obesity. Obesity leads to increasing insulin resistance which underlies both type 1 and type 2 diabetes. The implications are important to consider before embarking on any type 1 prevention programme that involves any pharmacological or surgical intervention. (Wilkin TJ - Diabetologia 2001).

• Support for the principal prediction of the Accelerator Hypothesis: Among children who develop Type 1 diabetes, those of higher body mass index (BMI) develop it younger - true acceleration. (Kibirige M - Diabetes Care 2003; Editorial by Arlan Rosenbloom, same issue).

• Further independent support for the Accelerator Hypothesis: This includes evidence that waist circumference is greater in children who develop type 1 diabetes. It satisfies another prediction that the age-adjusted BMI at presentation will rise as the environmental accelerator (body mass) increases over time. (Betts P - Diabetic Medicine 2005; editorial by Dennis Daneman, same issue).

• A closely reasoned plea, with a group of international opinion leaders, to consider lifestyle change or insulin sensitising drugs (as proof of principle) in the prevention/management of type 1 diabetes: Weight gain appears to be an important environmental accelerator contributing to the increase in type 1, as well as type 2 diabetes, and lifestyle intervention, clearly effective in type 2 diabetes, should now be trialled in type 1 before embarking on further trials using more aggressive forms of treatment such as immunotherapy or islet cell transplant. (Wilkin TJ - Diabetes Care 2004)

• A recent update reviewing progress with the hypothesis, expanding on the concept of tempo and addressing the critiques that have challenged it: There are now over 100 articles in the literature referring to or testing the Accelerator Hypothesis. The focus of the hypothesis remains where it started - with the concept of tempo as it relates to the loss of the insulin-secreting beta cells. (Wilkin TJ - International Journal of Obesity 2009)