This document discusses methods for analyzing regional fat distribution and body shape among Maya populations. It notes limitations of BMI and advocates using skinfold thickness measurements and the Healy-Tanner method to assess body size and shape. This method uses principal component analysis on log-transformed skinfold residuals to determine fat distribution patterns independent of total fatness. The document questions why BMI is still predominantly used and not other methods like those proposed by Garn, Tanner, and Frisancho that can provide more detailed information on chronic disease risk factors.

1. Health and fat patterning among the Maya: a
biocultural analysis of the epidemic of obesity
among this group
Ines Varela-Silva1, Hankook Kim1, Hugo Azcorra2, Hannah
Wilson3, Federico Dickinson2, Barry Bogin1
1Loughborough University, UK; 2CINVESTAV, Mexico, 3Northwestern University, USA
m.i.o.varela-silva@lboro.ac.uk

3. Regional distribution of fat = different risk factors
Android (Apple) vs.
Gynoid (Pear) Obesity
Vague J. Presse Med 1947;30:339–340.

4. Subcutaneous
adipose tissue
Front
Visceral adipose
tissue
Lemieux l, et al. Ann Endocrinol. 2001;62:255-261

5. Background
• Limitations of BMI: i) stature dependent; ii) leg-length dependent;
iii) weight reflects bone/muscle, not just fat (Garn et al 1986)
• Rates of fat change (…) differ from skinfold to skinfold and, to a
lesser extent, between sexes (Garn et al, 1987)
• Central adiposity – more associated with immune function than
extremity adiposity (Wells and Cortina-Borja, 2013).
• Stunted children are more likely to deposit fat centrally when
entering puberty, a significant risk factor for chronic diseases
(Hoffman et al, 2007)
• Skinfold thickness: as good as DXA when measuring adiposity
contributions to insulin resistance (Addo et al 2012)

7. http://bit.ly/1g2CJTX

8. Who are the Maya?
• One of the largest ethnic groups of
Guatemala, Mexico and Belize
• Long history of social, economic, and
political repression

11. Los Angeles,
California
Indiantown,
Florida

12. Mean height of Maya samples and mean
height of NHANES reference data
155
150
145
140
135
130
125
120
115
110
105
100
mean diff. = 10.24 cm
6 7 8 9 10 11 12
Age (years)
Height (cm)
Maya-Guat Maya-USA1992 Maya-USA2000 NHANES
NHANES

13. Mean body mass index (BMI) of Maya samples
and mean BMI of NHANES reference data
24
22
20
18
16
14
6 7 8 9 10 11 12
Age (years)
Body Mass Index
Maya-Guat Maya-USA1992 Maya-USA2000 NHANES

14. Research questions
• Why is BMI still the “queen” measure?
• Why critical thinking as stopped on this front?
• Why are we not reading Garn, Tanner, Frisancho
and others?
• What can we do to make it better?

16. Healy and Tanner method (1981)
• It allows for the description of fat distribution differences between
individuals or groups independent of their degree of total fatness
• the measure of shape is described as everything residual to size
– Total fatness= SIZE
– Residuals of SIZE= SHAPE
• It avoids problems related to units of measurement and differences
in the coefficients of variation for each variable (Bogin & Sullivan
1986)

17. Calculation of BODY SIZE (how much fat?)
1. Each skinfold (mm) is transformed into its natural log: loge
2. Calculate the mean of the log-transformed skinfold values
(Loge Tri + Loge Bic…Loge calf/number of skinfolds)
3. Use this new variable “Mean of all log-transformed skinfolds” for
your analysis

18. Calculation of BODY SHAPE (where is the fat?)
1. Run a regression for each log-transformed skinfold
• Dependent variable= Mean of ALL Log-transformed skinfolds
• Independent variables: each of the log-transformed skinfolds
• Save the unstandardized residuals for each log-transformed skinfolds
2. Run a Principal Component Analysis (PCA) using the residuals of
each log-transformed skinfolds
• Make sure the PCA assumptions are met (Andy Field’s statistics book)
• Save the factor scores on the database
3. Use the “FACTOR SCORES for further analysis on each component

24. WHY ARE WE NOT DOING MORE ON THIS?
WHY ARE WE STILL STUCK ON BMI?
- Most of the studies are not collecting
enough skinfolds
- Sample sizes need to be large

25. Summary: Healy and Tanner method
• Robust method to assess regional distribution of fat
• Minimum of 10-15 participants per variable analysed
• At least 4 skinfolds, but more is better
• Large samples are preferable
• PCA assumptions followed – otherwise results are meaningless
• Age added as a covariate in all factor scores analysis
• Always check for stunting…

26. Alternatives to Healy and Tanner
And…upper-arm measurements

27. Alternatives to Healy & Tanner

28. IMPACT OF OUR RESEARCH

29. http://mayaproject.org.uk

30. Maya Project Mission
Research
Excellent research,
aiming to improve
the quality of life of
the Maya
Training/teaching
Programmes for
teachers, health
personal,
researchers and
community leaders
Community
On-site
implementation of
programmes.
Working with
communities
Participatory Action Research

31. Maya Project Mission: Impact
Dissemination of
results
Seminars
Art exhibitions
Other cultural events
http://figshare.com/articles/Papers/817125

32. Impact and dissemination

33. Impact and dissemination

34. Impact and dissemination

35. See it here, buy it here
http://mayaproject.org.uk/the-maya-project-book/