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Will Dieting Cure The Obesity Epidemic? Traci Mann, Ph.D. University of Minnesota Department of Psychology.

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Presentation on theme: "Will Dieting Cure The Obesity Epidemic? Traci Mann, Ph.D. University of Minnesota Department of Psychology."— Presentation transcript:

1 Will Dieting Cure The Obesity Epidemic? Traci Mann, Ph.D. University of Minnesota Department of Psychology

2 No Traci Mann, Ph.D. University of Minnesota Department of Psychology

3 Obesity Rates , U.S

4

5

6 Definitions of Diet Success (Example: 200 pound woman, 55, BMI = 33) YearsStandardPounds to Lose WeightBMI 1940sMetropolitan Life Insurance Tables

7 Definitions of Diet Success (Example: 200 pound woman, 55, BMI = 33) YearsStandardPounds to Lose WeightBMI 1940sMetropolitan Life Insurance Tables sLose 40 pounds

8 Definitions of Diet Success (Example: 200 pound woman, 55, BMI = 33) YearsStandardPounds to Lose WeightBMI 1940sMetropolitan Life Insurance Tables sLose 40 pounds sLose 20 pounds sLose 10% of starting weight

9 Definitions of Diet Success (Example: 200 pound woman, 55, BMI = 33) YearsStandardPounds to Lose WeightBMI 1940sMetropolitan Life Insurance Tables sLose 40 pounds sLose 20 pounds sLose 10% of starting weight Lose 5% of starting weight

10 Weight Loss Maintenance:18 Months

11

12 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:

13 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:

14 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%

15 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

16 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

17 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.

18 Bias III: Participation in Additional Diets Independent Evidence: Survey of Dieters 60% 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

19 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

20 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

21 Stress Insulin resistance Increased food intake Decreased Physical Activity Disrupted sleep Weight Gain Cortisol increase Visceral fat deposition HPA axis activation SNS activation sAA increase Increased caloric absorption Mechanisms of Stress-induced Weight Gain

22 1.Does dieting cause stress? 2.Are biological mechanisms involved? 3.What is it about dieting that is stressful? Three Questions

23 Study Design MonitoringNo Monitoring Restricting Classic DietFood Provided No Restricting Food DiaryControl

24 Sample n = 121 females Mean age: 22 Mean BMI: 25 Procedures 1. Pre-diet questionnaires and 2 days of saliva sampling 2. Three weeks of assigned diet 3. Post-diet questionnaires and 2 days of saliva sampling Sample & Procedures

25 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

26 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 Checks Only one non- restricting condition monitored calories

27 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)

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

29

30 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 ones diet increases perceived stress Restricting ones diet increases cortisol Conclusions

31 Monitoring: Increased perceived stress –Its another hassle –Each food item recorded is a failure –We eat more than we realize Restricting: Increased cortisol –Cortisols main job: Gluconeogenesis Why Are These Behaviors Stressful?

32 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 Arent These Behaviors Stressful?

33 Obesity Rates , U.S.

34 Mortality Rates , U.S. Obesity Rates , U.S. Deaths per 100,000

35 Mortality Age 18+, U.S. Deaths per 100,000 Cardiovascular Cancers All Causes Diabetes

36 Copyright restrictions may apply. Relative Risks of Mortality by BMI Category and Age Ages Ages 60-69Ages 70 < < < BMI Ranges Relative Risk * * * *

37 37

38 Obesity-Health Confounds –Sedentary lifestyle –Weight cycling –Under-use of the medical system –Poverty/SES Mortality Rate

39 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? Yes No

40 Is Dieting Safe? Controlling for BMI, chronic dieting is associated with: –Cardiovascular disease 1 –Myocardial infarction 2 –Stroke 2 –Diabetes 2 –Increased blood pressure 3 –Increased HDL 4 –Suppressed immune function 5 –All-cause mortality Hamm, Shekelle, & Stamler, French et al., Olson et al., Kajioka, Tsuzuku, Shimokata, & Sato, Shade et al., Andres, Muller, & Sorkin, Blair, Shaten, Brownell, Collins, & Lissner, Lee & Paffenbarger, Pamuk, Williamson, Serdula, Madans, & Byers, 1993

41 Kiefer et al., 2008

42 Aglets

43 Kiefer et al., 2008 Telomeres = aglets for your chromosomes Marker & mediator of biological aging Aglets

44 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

45 Effects of Exercise on Health Lost expected amount of weight Resting Heart RateImproved Systolic Blood PressureImproved Diastolic Blood PressureImproved Waist CircumferenceImproved Cardio-Respiratory FitnessImproved

46 Effects of Exercise on Health Lost expected amount of weight Didnt lose expected amount of weight Resting Heart RateImproved Systolic Blood PressureImproved Diastolic Blood PressureImproved Waist CircumferenceImproved Cardio-Respiratory FitnessImproved

47 Funders National 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 Assistants Danielle Vinas Jeff Hunger Kate E. Byrne Haltom Acknowledgements Main Collaborators Janet Tomiyama Andrew Ward Defrayer of Cortisol Assay Costs Clemens Kirschbaum


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