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Predicting body composition using simple measurement techniques. Tim Johnson, Javier Navarro, Idiong idongesit , Mark Weeks. Data . - PowerPoint PPT Presentation
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PREDICTING BODY COMPOSITION USING SIMPLE MEASUREMENT
TECHNIQUES
TIM JOHNSON, JAVIER NAVARRO, IDIONG IDONGESIT, MARK WEEKS
DATA • IN 1985 A STUDY ABOUT PREDICTING BODY FAT DISTRIBUTION
FROM EASILY OBTAINABLE MEASUREMENTS WAS UNDERTAKEN. 252 MALE SUBJECTS VOLUNTEERED FOR THE STUDY. OVER THE YEARS ONE INSTANCE WAS LOST.• RECORDS WERE RECORDED FOR THE FOLLOWING VITAL
STATISTICS:1. Density 6. Neck 11. Knee2. Percent Body Fat
7. Chest 12. Ankle
3. Age (years) 8. Abdomen 13. Biceps4. Weight (lbs) 9. Hip 14. Forearm5. Height (inches) 10. Thigh 15. WristItems 6-15 measured in
centimeters
CALCULATIONS
DENSITY 𝐷=
𝑊 𝑎𝑖𝑟
{[ (𝑊𝑎𝑖𝑟−𝑊𝑤𝑎𝑡𝑒𝑟 )𝑐 . 𝑓 . ]− 𝐿𝑢𝑛𝑔𝑣𝑜𝑙}
BODY FAT PERCENTAGE𝐷=
1
[( 𝐴𝑎 )+(𝐵𝑏 )]
where, W is weight in water or airc.f. is water temperature correction factor ~.997 at 76-78 degrees FahrenheitThis method of determining D, density, is considered the gold standard.
where, A= proportion of lean body tissuea= density of lean ~1.1 gm/cm3
B= proportion of fat body tissueb= density of fat ~0.90 gm/cm3
AND % Body Fat = 495/D – 400OR B = (1/D)*[ab/(a-b)]-[b/(a-b)]
EQUATION DEVELOPED FOR LEAN BODY WEIGHT
LBW=17.298 <numerical offset>+.89946(Weight)
-.2783(age) +.002617(age)2 <Age factor>
+17.819(Height) <Height factor>
-.6798(Waist-Wrist)Stepwise multiple regression techniques were used to develop this structural equation back in the 1980’s.
OVERVIEW OF THE DATA
HOW DOES AGE COMPARE TO DENSITY
HOW DOES HEIGHT COMPARE TO DENSITY?
AGE VS WEIGHT
HEIGHT VS WEIGHT
WEIGHT VS NECK
WEIGHT VS DENSITY
DENSITY VS WAIST
HOW DOES AGE COMPARE TO %BODY FAT
TRAINING SET DENSITY DISTRIBUTION
TRAINING SET %BODYFAT DISTRIBUTION
TEST SET’S %BODYFAT DISTRIBUTION
SIMPLE LINEAR REGRESSION
VISUALIZE ERRORS
HEALTH FREAK
CONSIDER THIS• THE PREVIOUS NEARLY PERFECT PREDICTION LOOSES THE EASE OF
PREDICTION USING SIMPLE MEASUREMENT TECHNIQUES. THE FORMULA ALSO USES THE GOLD STANDARD: DENSITY AS THE BASIS FOR THE PREDICTION.
• CAN SIMPLE MEASUREMENT TECHNIQUES PREDICTING %BODYFAT BE FOUND USING WEKA?
• THE FOLLOWING SLIDES CHECK OUT THAT POSSIBILITY• FIRST USING THE WAIST MEASUREMENT• THEN USING THE WAIST AND THE WRIST MEASUREMENTS • AND FINALLY USING ALL THE MEASUREMENTS BUT DENSITY
TRAINING SET WAIST
TRAINING SET WAIST & WRIST
TRAINING SET ALL BUT…
COULD WE DUPLICATE THE 1985 RESULTS?
ONE MEASUREMENT BODY FAT
TWO MEASUREMENT BODY FAT
ALL BUT PREDICT BODY FAT
1985
USING M5P RULES
Here we use machine learning to develop rules: Weka detects two using waist > or < 87.1 cm circumference. Overall accuracy is at a regression value of 85.33%
CLUSTERING—SIMPLE K MEANS
SUMMARY• THE FORMULA WITH THE BEST RESULTS BASED ITS PREDICTIVE
ABILITY UPON THE DENSITY OF THE INDIVIDUAL IN AIR AND WATER.• WE LOSE THE GOAL OF THE 1985 STUDY OF BEING ABLE TO
PREDICT THE PERCENT OF BODY FAT BASED ON EASILY ACCESSIBLE MEASUREMENTS. • BY ELIMINATING THE DENSITY CATEGORY THE CALCULATION
ENGINE IS FORCED TO UTILIZE THE REMAINING CATEGORIES. • THE RESULTING CORRELATION PROBABILITY SHOW THE
ACCURACY ATTAINED USING EASILY OBTAINABLE MEASUREMENTS WITHOUT OVER FITTING. • SOME EVIDENCE OF CLUSTERING WAS FOUND AND COMPARED
TO THE RULES.
REFERENCES
• “GENERALIZED BODY COMPOSITION PREDICTION EQUATION FOR MEN USING SIMPLE MEASUREMENT TECHNIQUES” K. W. PENROSE, ET AL. FACSM, HUMAN PERFORMANCE RESEARCH CENTER, BRIGHAM YOUNG UNIVERSITY, “MEDICINE AND SCIENCE IN SPORTS AND EXERCISE, V17, NO. 2, APRIL 1985, P. 189.
• “BODYFAT”, R.W.JOHNSON, DEPT OF MATHEMATICS & COMPUTER SCIENCE, SOUTH DAKOTA SCHOOL OF MINES AND TECHNOLOGY, HOSTED BY STATLIB, DEPARTMENT OF STATISTICS, CARNEGIE MELLON UNIVERSITY, HTTP://LIB.STAT.CMU.EDU/MODULES.PHP, ACCESSED 3/23/2014.