Dietary Energy Density: A Mediator or Predictor of Abdominal Obesity

Daurice A. Grossniklaus, RN, MEd, PhD1

Sandra B. Dunbar, RN, DSN, FAAN, FAHA1

Rebecca Gary, RN, PhD, FAHA1

Beth C. Tohill, PhD, MSPH2

Jennifer Frediani, MS, RD, LD1

Melinda K. Higgins, PhD1

1Emory University 2Atlanta, Georgia, USA

Sponsors

Alpha Epsilon Chapter, Sigma Theta Tau International

Small Grant Award, Southern Nurses Research Society

Dorothy Cornelius Research Award, American Nurses Foundation

Isabel Hampton Robb Scholarship, Nurses Educational Funds, Inc.

NIH, NINR, NRSA (1F31NR010159-01A1)

Supported in part by PHS Grant UL1 RR025008 Clinical and Translational Science Award program and PHS Grant M01 RR0039 General Clinical Research Center program, NIH, National Center for Research Resources

Background

Abdominal obesity (AO)

• Associated with cardiometabolic disease (Grundy et al., 2005)

• Prevalence is increasing in US and Europe (Li et al., 2007)

• Waist circumference (WC) > 102 cm for men, > 88 cm for women (National Cholesterol Education Program (NCEP), 2001; NIH, 1998)

Associated factors

• Psychological distress (Kuo et al., 2007)

• Chronic activity of the stress response (hypothalamic-pituitary-adrenocortical [HPA] axis) (Dallman et al., 2004)

• Increased dietary energy density (DED) (Cuco et al., 2001; Ledikwe et al., 2006)

Purposes

• Compare adults with AO versus adults without AO on bio-psychological factors (depressive symptoms; HPA axis activity)

• Test DED for independent association with AO

• Test DED as a mediator between bio-psychological factors (depressive symptoms; HPA activity) and AO

DED: A Potential Mediator Between Bio-psychological Factors and Abdominal Obesity

Bio-psychological factors

•Depressive symptoms•HPA axis activity

Abdominal obesity•Waist circumference

Potential mediator•Dietary energy densityEnvironmental

demands

Individual characteristics

(Cohen, Kessler, & Gordon, 1995)

Adipogenesis

Depressive Symptoms are Associated with…

• Preferences for high fat and high carbohydrate foods

(Benton, 2002)

• Processed foods, energy dense diets, low dietary quality

(Jacka et al., 2010; Grossniklaus et al., in press)

• Alcohol intake (Siegel et al., 2000 ; Strine et al., 2008)

• Abdominal adiposity independent of body mass index

(BMI) (Ma & Xiao, 2010)

HPA Axis Activity, Dietary Energy Density, and Abdominal Obesity

• Chronic psychological distress may result in prolonged release of cortisol (Dallman et al., 2004)

• ~ 50% of individuals with depression over secrete cortisol (Cowen, 2002)

• Elevated cortisol associated with preferences for high energy dense “comfort” foods (La Fleur et al., 2004)

• Glucocorticoid receptors are highly prevalent in abdominal adipose (Dallman et al., 2004)

• Cortisol promotes the expansion of abdominal adiposity (Dallman, Akana et al., 2004; Dallman, La Fleur et al., 2004)

Dietary Energy Density is Associated with…

• Lower dietary quality (Cuco et al., 2001; Ledikwe et al., 2006)

• Excess energy intake (Poppitt & Prentice, 1996)

• Higher BMI among women and trend among men (Mendoza et al., 2007)

• Larger WC in women and men (Mendoza et al., 2007)

Dietary Energy Density: Equal calories and % macronutrients

Image courtesy of Dr. BJ Rolls

DED = 0.68

kcal/gram

DED = 1.48

kcal/gram

50 kcal 100 kcal 200 kcal

100 kcal 200 kcal 400 kcal

150 gram salads

Low DED

0.33 kcal/g

300 gram salads

Medium DED

0.67 kcal/g

High DED

1.33 kcal/g

Dietary Energy Density: Equal Weight

Image courtesy of Dr. BJ Rolls

Methods

• Prospective, cross-sectional study

• Approved by university Institutional Review Board

• Adults (18-65 years old)

• Inclusion Criteria: – BMI ≥ 25.0 kg/m2

• Exclusion Criteria: – Physical activity ≥ 90 minutes/week

– Pregnant or breastfeeding

– Treated with steroids, valproic acid, phenothiazines, or antidepressants

– History of diabetes, liposuction, bariatric or abdominal surgery

Variables and Measures• Individual and health factors

– Age, gender, race

• Bio-psychological factors – Depressive symptoms (Beck Depression Inventory II [BDI-II])

– HPA activity (Morning cortisol)

• Potential mediator– Dietary energy density (Weighed three-day food record)

• Abdominal obesity– Waist circumference (WC)

Bio-psychological Factors: Depressive Symptoms

Beck Depression Inventory – II (BDI-II)

# of items 21

Response (min-max) 0-3

Minimum 0

Maximum 63

Interpretation Higher scores, more severe depressive symptoms

Cronbach’s α 0.91

Beck et al., 1996; Steer et al., 1997

Bio-psychological Factors: HPA Activity

• AM cortisol level

• Saliva sample– In salivettes

– On awakening

• Cortisol reference range 0.18-0.95 µg/dl (Salimetrics)

Potential Mediator: Dietary Energy Density

• Weighed three-day food record

– Total daily caloric intake/total daily weight of food and beverages (Yao

and Roberts, 2001)

– Reported Adequate Caloric Intake (RACI)

• Predicted energy expenditure/reported caloric intake (Harris & Benedict, 1919)

• RACI ≥ 1 reported caloric intake less than predicted energy expenditure

Abdominal Obesity: Waist Circumference

• Standardized National Health and Nutrition Survey (NHANES) procedure(National Center for Health Statistics)

• Landmark: Uppermost lateral border of right iliac crest • Intra-rater reliability = .96

Procedure

Visit 1 with Study Nurse

Informed consent

Instructed how to use food scale and keep food record

Instructed how to collect and store saliva sample

Measure height, weight, and waist circumference

Completed questionnaires

Kept weighed food record

Collected saliva sample

Turn in completed questionnaires

Turned in saliva sample

Reviewed food record

Visit 2 with Study Nurse

Three Days at Home

Post Visit

Scored BDI-II -Alert protocol

Sample labeled, centrifuged & froze

Food record reviewed by dietitian

Calculated DED and RACI values

• Descriptive statistics

• Mann-Whitney Z scores

• Hierarchical linear regression to test DED for an independent association with AO while controlling for depressive symptoms and food and beverage weight (Mendoza et al, 2007)

• 3 approaches to test DED as a mediating variable (Baron & Kenny, 1986; Preacher & Hayes, 2004; Sobel, 1982)

Data Analysis

Individual Characteristics (N=87) Variable Mean ± SD

N (%)Range

Sex 64 (73.6) women

Race 44 (50.6) African American

Age (years) 41.3 ± 10.2 20 – 64

BMI (kg/m2)WomenMen

32.5 ± 6.531.0 ± 4.5

25.1 – 52.024.6 – 43.1

EducationCollege grad/post-graduate 51 (58.7)

Total combined family income (US$)≥ $60,000 46 (52.9)

Hypertension 18 (20.7)

Depressive symptoms (BDI-II ≥ 14) 19 (21.8)

Dietary FactorsVariable Mean ± SD Range

Food and beverage intake (kcal)

2029.8 ± 589.0 1066.2 – 3731.5

Food and beverage weight (g)Dietary energy density (kcal/g)

2864.0 ± 864.9

0.75 ± 0.22

1062.6 – 5972.8

0.32 – 1.31

Reported inadequate caloric intake (RACI ≥ 1)

N (%)

51 (58.6)

Waist circumference (cm) Mean + SD Range

All (n=87) 103.2 + 14.3 78.3 – 140.0

Men (n=23) 103.38 + 12.7 89.3 – 140.0

Women (n=64) 103.19 + 14.9 78.3 – 140.0

Abdominal obesity N (%)

All 64 (73.6%)

Men (>102 cm) 10 (43.5%)

Women (>88 cm) 54 (84.8%)

Waist Circumference & Abdominal Obesity

Depressive Symptoms, Cortisol, and DED by Abdominal Obesity

Variable Without AO(n = 23)

Median (Range)

With AO(n = 64)

Median (Range)

Mann-Whitney Z

BDI-II 5.0 (0 – 21.0) 7.0 (0 – 42.0) –2.003*

AM cortisol (µg/dl) .41 (.08 – 1.73)a .59 (.15 – 2.21)b –2.286*

DED (kcal/g) .75 (.32 – 1.17) .73 (.41 – 1.31) –0.337

an = 21. bn = 58.

*p ≤ .05.

DED: Possible Independent Association with Waist Circumference

Variable B SE B β

Step 1 – Covariates

BDI-II 0.15 .05 .31*

Food & beverage weight (g) 2.3E–4 8.6E–5 .28*

R2=.135; F=6.504*

Step 2 – DED

BDI-II .14 .05 .29*

Food & beverage weight (g) 3.5E–4 9.3E–5 .42*

DED (kcal/g) .21 .08 .30*

∆ R2=.070; F for ∆ R2=7.276*; R2=.206; F=7.090*

DED: Possible Mediator between Depressive Symptoms and Waist Circumference

Method of Analysis

Baron and Kenny method

Coefficient Standard error T-statistic P-value

b (WC, BDI-II) .12 .05 2.33 .02

b(DED, BDI-II) .02 .02 1.46 .15

b(WC, DED. BDI-II) .35 .34 1.03 .31

b(WC, BDI-II. DED) .11 .05 2.15 .03

Value Standard error Z-statistic P-value

Sobel test .01 .01 .73 .46

Mean Standard error LL 95% CI UL 95% CI

Bootstrap .01 .01 –.01 .04

Conclusions

• Depressive symptoms in this sample were more common than in general US population

• Majority had WC measurements indicating abdominal obesity and increased relative risk of cardiovascular disease

• Although within the range of minimal depressive symptoms, adults with AO had greater depressive symptoms than adults without AO

• Although within the reference range, morning cortisol levels were higher in adults with AO vs adults without AO

Conclusions

• Dietary energy density was independently associated with abdominal obesity

• Dietary energy density did not mediate between depressive symptoms and abdominal obesity

Limitations

• Non-random sampling

• Underreporting of caloric intake may mask significant relationships

– Undereating

– Underrecording

– Underestimating

– Recording burden

• Challenge to collect saliva samples

Research Recommendations

• Develop and test comprehensive nursing approaches aimed at:

– Early recognition and reduction of depressive symptoms

– Reducing dietary energy density

Thank you!