Will Dieting Cure The Obesity Epidemic?

Traci Mann, Ph.D.University of Minnesota

Department of Psychology

No

Traci Mann, Ph.D.University of Minnesota

Department of Psychology

Obesity Rates 1980-2007, U.S.

1980 2007

Definitions of Diet Success(Example: 200 pound woman, 5’5”, BMI = 33)

Years Standard Pounds to Lose

Weight BMI

1940s Metropolitan Life Insurance Tables

66 134 23

Definitions of Diet Success(Example: 200 pound woman, 5’5”, BMI = 33)

Years Standard Pounds to Lose

Weight BMI

1940s Metropolitan Life Insurance Tables

66 134 23

1950s Lose 40 pounds 40 160 27

Definitions of Diet Success(Example: 200 pound woman, 5’5”, BMI = 33)

Years Standard Pounds to Lose

Weight BMI

1940s Metropolitan Life Insurance Tables

66 134 23

1950s Lose 40 pounds 40 160 27

1960s Lose 20 pounds 20 180 30

1970s Lose 10% of starting weight 20 180 30

Definitions of Diet Success(Example: 200 pound woman, 5’5”, BMI = 33)

Years Standard Pounds to Lose

Weight BMI

1940s Metropolitan Life Insurance Tables

66 134 23

1950s Lose 40 pounds 40 160 27

1960s Lose 20 pounds 20 180 30

1970s Lose 10% of starting weight 20 180 30

1995+ Lose 5% of starting weight 10 190 32

Weight Loss Maintenance:18 Months

Long-Term Diet Studies(Mann et al., 2008, American Psychologist)

• Studies with control groups (n=8)– Avg. weight change of dieters: Lost 2.3 lbs– Avg. weight change of controls:

• Studies without control groups (n=13)– Initial weight loss: 39 pounds– Ultimate gain-back:– % regain more than they lost:

Long-Term Diet Studies(Mann et al., 2008, American Psychologist)

• Studies with control groups (n=8)– Avg. weight change of dieters: Lost 2.3 lbs– Avg. weight change of controls: Gained 1.3 lbs

• Studies without control groups (n=13)– Initial weight loss: 39 pounds– Ultimate gain-back:– % regain more than they lost:

Long-Term Diet Studies(Mann et al., 2008, American Psychologist)

• Studies with control groups (n=8)– Avg. weight change of dieters: Lost 2.3 lbs– Avg. weight change of controls: Gained 1.3 lbs

• Studies without control groups (n=13)– Initial weight loss: 39 pounds– Ultimate gain-back: 32 pounds– % regain more than they lost: 31% to 64%

Sources of Bias in Diet Studies

1. Low rates of attendance at follow-ups

2. High rates of self-reported weight

3. Failure to account for additional diets

4. Confounding effects of diet with effects of exercise

Bias I: Follow-Up Rates

Independent evidence: The fewer follow-ups, the steeper the rate of regain

Follow-up rates in the 13 studies: Poor follow-up rate (<25%) in 3 studies Fair follow-up rate (30-50%) in 5 studies Good follow-up rate (70-88%) in 5 studies

Bias II: Self-Reported Weights

Independent evidence: People under-report their weight by about 8 pounds, and obese people tend to under-report by more than that.

61% of all weights in these studies were self-reported.

Bias III: Participation in Additional Diets

Independent Evidence: Survey of Dieters60% weighed more than starting weight at some point since diet

40% weigh more than starting weight now

Rates of participation in other diets 20% to 65% of participants (7 studies) 1 to 3 diets/year (3 studies) 3 studies did not report this

Bias IV: Confounding Diet and Exercise

Independent Evidence Strongest predictor of weight-loss maintenance >90% of successful maintainers use regular exercise

Rates of exercise in the 13 studies: 22% to 46% engaged in regular exercise 8 studies did not report on exercise

Dieting

Psychological Pathways

Biological Pathways

• Negative Calorie Balance

• Short-term Weight Loss

Weight Regain

• Decreased Metabolism

• Increased Food Intake

• Increased Fat Deposition

• Violation / Perceived Violation of Diet

• Cognitive Load

• Negative Affect

Overeating

Stress

• HPA Activation• SNS Activation• Negative Health Behaviors• Increased Food Intake

Biopsychosocial Pathways

Mechanisms of Diet Failure

• Leptin & Insulin Decrease• Ghrelin Increase

• Catabolic Inhibition

• Cholecystokinin Sensitivity• Anabolic Stimulation

Stress

Insulinresistance

Increased food intake

Decreased Physical Activity

Disrupted sleep

Weight Gain

Cortisolincrease

Visceral fatdeposition

HPA axisactivation

SNSactivation

sAAincrease

Increasedcaloric absorption

Mechanisms of Stress-induced Weight Gain

1. Does dieting cause stress?

2. Are biological mechanisms involved?

3. What is it about dieting that is stressful?

Three Questions

Study Design

Monitoring No Monitoring

Restricting Classic Diet Food Provided

No Restricting Food Diary Control

Samplen = 121 femalesMean age: 22Mean BMI: 25

Procedures1. Pre-diet questionnaires and 2 days of saliva sampling2. Three weeks of assigned diet3. Post-diet questionnaires and 2 days of saliva sampling

Sample & Procedures

• Psychological Stress: Perceived Stress Scale (Cohen et al, 1986)

• Biological Stress: Salivary Cortisol – Wake-up – Wake-up + 45 minutes– Wake-up + 12 hours

• Cortisol confounds: Alcohol, exercise, illness, etc.

Measures

• Sticking to 1200 kcal diet– Restricting conditions: 1260 kcal– Non-restricting condition: 1704 kcal

• Weight change– Restricting conditions: -1.9 lbs– Non-restricting conditions: +2.6 lbs

Manipulation ChecksOnly one non-restricting condition monitored calories

Perceived Stress: Main effect of monitoring

Monitoring diet: Perceived stress increased

Not monitoring diet: Perceived stress did not change

Total Cortisol Output: Main effect of restricting

Restricting diet: Cortisol output increased

Not restricting diet: Cortisol output did not change

Results(Tomiyama, Mann et al., 2010, Psychosomatic Medicine)

(Tomiyama, Mann et al., 2010, Psychosom Med)

(Tomiyama, Mann et al., 2010, Psychosom Med)

1. Does dieting cause stress?It did in this study

2. Are biological mechanisms involved?total cortisol output was involved in this study

3. What is it about dieting that is stressful?Monitoring one’s diet increases perceived stress

Restricting one’s diet increases cortisol

Conclusions

• Monitoring: Increased perceived stress– It’s another hassle

– Each food item recorded is a “failure”

– We eat more than we realize

• Restricting: Increased cortisol– Cortisol’s main job: Gluconeogenesis

Why Are These Behaviors Stressful?

• Monitoring: Did not increase cortisol– Maybe a prolonged increased in perceived stress would have?

• Restricting: Did not increase perceived stress– Correlational studies find it: but they confound the two tasks

– “Restricting Only” condition – provided free and delicious food

– Working successfully towards a goal – positive emotion

Why Aren’t These Behaviors Stressful?

Obesity Rates 1980-2007, U.S.

Mortality Rates 1980-2007, U.S.Obesity Rates 1980-2007, U.S.

Deaths per 100,000

Mortality Age 18+, U.S. Deaths per 100,000

CardiovascularCancers

All Causes

Diabetes

Copyright restrictions may apply.

Relative Risks of Mortality by BMI Category and Age

Ages 25-59 Ages 60-69 Ages ≥ 70

<18.5 25 30 35 35+ <18.5 25 30 35 35+ <18.5 25 30 35 35+

BMI Ranges

Relative Risk

* * * *

37

Obesity-Health Confounds

– Sedentary lifestyle

– Weight cycling

– Under-use of the medical system

– Poverty/SES

Mor

talit

y R

ate

Should we recommend

dieting to treat obesity?

Do not recommend

Is dieting safe?

Is dieting effective?

Do not recommend

Do not recommend

Recommend

Is obesity unhealthy?

YesYes Yes

NoNoNo

Is Dieting Safe?

Controlling for BMI, chronic dieting is associated with:– Cardiovascular disease1

– Myocardial infarction2

– Stroke2

– Diabetes2

– Increased blood pressure3

– Increased HDL4

– Suppressed immune function5

– All-cause mortality6-9

1Hamm, Shekelle, & Stamler, 1989 2French et al., 1997 3Olson et al., 2000 4Kajioka, Tsuzuku, Shimokata, & Sato, 2002 5Shade et al., 2004 6Andres, Muller, & Sorkin, 1993 7Blair, Shaten, Brownell, Collins, & Lissner, 1993 8Lee & Paffenbarger, 1992 9Pamuk,

Williamson, Serdula, Madans, & Byers, 1993

Kiefer et al., 2008

Kiefer et al., 2008

Aglets

Kiefer et al., 2008

•Telomeres = aglets for your chromosomes•Marker & mediator of biological aging

Aglets

Dieting is Associated with Telomere Length

Kiefer et al., 2008

•Telomeres = aglets for your chromosomes•Marker & mediator of biological aging•More dietary restraint, shorter telomeres

Aglets

Effects of Exercise on Health

Lost “expected” amount of weight

Resting Heart Rate Improved

Systolic Blood Pressure Improved

Diastolic Blood Pressure Improved

Waist Circumference Improved

Cardio-Respiratory Fitness Improved

Effects of Exercise on Health

Lost “expected” amount of weight

Didn’t lose “expected” amount of weight

Resting Heart Rate Improved Improved

Systolic Blood Pressure Improved Improved

Diastolic Blood Pressure Improved Improved

Waist Circumference Improved Improved

Cardio-Respiratory Fitness Improved Improved

FundersNational Institute of Mental Health

National Heart, Lung, and Blood Institute

US Department of Agriculture

University of Minnesota

UCLA Health and Eating Lab UMN

Health and Eating Lab UCLA Students in Psychology of Eating

Research AssistantsDanielle VinasJeff HungerKate E. Byrne Haltom

Acknowledgements

Main CollaboratorsJanet TomiyamaAndrew Ward

Defrayer of Cortisol Assay Costs Clemens Kirschbaum