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Objectives. Market to you a calculator for determining child weight statusIdentify issues / barriers and answer questionsKeep you engagedVaguely keep to time. Weight Status. Strong association between weight status and health / diseaseSignificant (public) health issueCategorisation:Underweight / thinNormal weightOverweightObeseMorbidly obese.
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1. Child Weight Status CalculationY&H National Obesity Forum18-Feb-2010 Dr Rory O’ConorConsultant in Public HealthWakefield District PCTYorkshire & Humber PHO
2. Objectives Market to you a calculator for determining child weight status
Identify issues / barriers and answer questions
Keep you engaged
Vaguely keep to time
3. Weight Status Strong association between weight status and health / disease
Significant (public) health issue
Categorisation:
Underweight / thin
Normal weight
Overweight
Obese
Morbidly obese
4. Measurement of weight status Visual judgement “looks fat”, “looks thin”
Quantification
Body Mass Index (height/weight squared)
Waist circumference
Skinfold thickness
Other measures
5. Body Mass Index Has stood test of time
Research body of evidence
Adults:
Underweight BMI < 18.5 m/kg2
Overweight BMI > 25 m/kg2
Obese BMI > 30 m/kg2
Morbidly Obese BMI > 40 m/kg2
Simple numbers, relatively simple formula
6. Example Mother and daughter
Mother age 25 yrs, height 5’4” = 1.63m 46 kg = 6st 5lb
Daughter age 10 yrs, height 4’11” = 1.2m
25 kg = 3st 8lb
What is the weight status of the mother and her daughter?
Ps: after next slide you decideUnderweight, normal, overweight/obese
7. Example Mother and daughter
Mother age 25 yrs, height 5’4” = 1.63m 46 kg = 6st 5lb
BMI = 46/(1.63*1.63) = 17.3
Daughter age 10 yrs, height 4’11” = 1.2m
25 kg = 3st 8lb
BMI = 25/(1.2*1.2) = 17.4
What is the weight status of the mother and her daughter?
8. BMI in children Children grow !
Describe / show child height/weight charts
Ideal BMI keeps changing
What to do?
Visual estimation (v poor guide)
Comparison of centile lines for weight and height
Child BMI chart
algorithms
9. Example Mother and daughter
Mother age 25 yrs, height 5’4” = 1.63m 46 kg = 6st 5lb
BMI = 46/(1.63*1.63) = 17.3
Daughter age 10 yrs, height 4’11” = 1.2m
25 kg = 3st 8lb
BMI = 25/(1.2*1.2) = 17.4
What is the weight status of the mother and her daughter?
11. Algorithms for child BMI Charts from Child Growth Foundation
Expensive / copyright / not electronic
Tim Cole / IOTF – LMS addin for Excel
Requires analytical skills
Unsuitable for health visitors, teachers, parents and children
Unsuitable for incorporating into programs
Rory O’Conor derived formula
Complicated formula
Derived from LMS data using regression techniques
Usable direct in Excel or clinical systems
US CDC Teen and Child BMI Calculator
Another online calculator using LMS method and CDC2000 data
12. Example Mother and daughter
Mother age 25 yrs, height 5’4” = 1.63m 46 kg = 6st 5lb
BMI = 46/(1.63*1.63) = 17.3
Daughter age 10 yrs, height 4’11” = 1.2m
25 kg = 3st 8lb
BMI = 25/(1.2*1.2) = 17.4
What is the weight status of the mother and her daughter?
13. Instances of Rory’s formula Original spreadsheet
Demo
JAVA program
Demo
Download and applet
Available for download from
www.btinternet.com/~rory.oconor/obesity/
14. Requires JAVA – call IT support
15. Usability Formula is complex (but accurate) and can be hidden
Excel spreadsheet & JAVA program usable
By all, even children and parents
Greater access and feedback about “correct” weight status, greater opportunity for change
Formula copes with change as child ages and grows
Benefit – access to accurate child weight status
16. Future potential Use of formulae / programs on other websites
Incorporation of formula into clinical systems
General Practice
Child Health
Education
Incorporation into other products
iPoD apps
Scales
WII boards etc
Internationalisation and improvement of JAVA program
Addition of centile and z score values
17. Conclusion Formula for adult equivalent BMI provides an accurate and usable measurement of child weight status
The formula is already available in a spreadsheet and JAVA calculator
The formula can potentially be used in clinical systems and user equipment such as scales
18. Request Use it
Research interest
Write article in journal about use
Marketing
Get into GP/Child health systems
Get into scales
Website
Use it
19. Contact details Website
www.btinternet.com/~rory.oconor/obesity/
Email
roc501@york.ac.uk
Rory.oconor@wdpct.nhs.uk
20. Technical Annex See website for further details
Formula calculates “adult equivalent BMI” which is the BMI that a child maintaining the same centile would have at age 18 years
Formula has 18 terms, non-linear regression
Formula derived using 3474 data points for ages 2 to 18 years and adult BMI between 17 to 40
R squared 0.995, max error BMI +/- 2.6
Recommendation: Independent quality assurance