Health Psychology

Chapter 15: Eating & Dieting Mansfield University Dr. Craig, Instructor

1

The Digestive System

 Human body converts foods (plant and animal tissue) into usable components (fats, proteins, carbohydrates, vitamins & minerals).

 Materials transported through bloodstream to need areas or to be stored  Salivary glands- part of taste sensation, contains enzyme to break down starches  Peristalsis-rhythmic contraction and relaxation of muscles lining digestive tract starting in esophagus  in the stomach it moves food and mix with gastric secretions (high acidity) such as pepsin which works on proteins.

Digestion Continued

   Small Intestine • balance pH of “stomach mix” by secreting alkalinic pancreatic juices that also help digest CHO and fats • • absorption of starches fats broken down by bile salts stored in gall bladder and made in liver • fluids absorbed and nutrients/electrolytes extracted Large Intestine • further absorption of H20 and manufacture some vitamins The Brain • Hypothalamus and hyper insulin secretion-- adipose • Cholecystokin (CCK)- satiety; Leptin- reduced food intake, increased activity levels

Weight Maintenance

 Weight flux: calories burned =calories consumed  Consumed  CHO (sugar, starches) 4 kcals/gram    Proteins Fats Alcohol 4 kcals/gram 9 kcals/gram 7 kcals/gram • Fats= highest concentration of kcals, alcohol most selectively taken by system  Burned •    daily metabolism activities of daily living exercise metabolism varies individually, and under different conditions  consider weight loss and gain research!!

Experimental Starvation

   Ancel Keys Research on Normals Design • • 3 months as usual eating Reduce ration until 75% of current weight (half rationing) • 3 months refeeding Results • rapid weight loss pace originally that slowed to a crawl”- had to cut under half rations to lose weight • • • irritable, aggressive, neglectful of hygeine appearance food obsessed during refeeding, most men over ate and gain more than previous normal weight • many did not return to previous mood state

Experimental Overeating

  Sims Research- to gain 20-30 pounds • population of prisoners Findings  initial weight gain with the doubling of diet…. After that a slow down in weight gain requiring even more.

 Food became repulsive  after study.. Most returned quickly to normal weight

Obesity

 What can these experiments tells us about common perceptions of eating and obesity?

• Metabolism changes with eating… not fast to change… suggests we have individual levels of weight we naturally maintain.  Measuring Obesity  weight-- muscle, bone and adipose tissue (fat)  key is to measure fat and not other components  difficult to to with out expensive equipment • CAT scan, MRI, Dual-Xray, Ultrasound  How can we know then?

Measuring Obesity- Useful measurement

   Skinfold technique- +/-3.5% Water Immersion- the archimedes principle  Waist-hip Ratio- relative distribution of fat, but not fatness though • carry fat high (apple) or low (pear) Body Mass Index- kg /m 2 -- a measure of body density relative to height. (See also 15.1 in text) • 27.8 women 27.3 men • who doesn’t this work well for?

 Met Life Height-Weight charts (15.2)

Obesity on the Increase

    Overall obseity in US has increased by 1/3 in the past 20 years People (more women) increasingly conscious of and dissatisfied with bodies even if weight is normal.

 On diet even if BMI<25 Dieter have 50% more weight flux than non dieters Increasing use of dangerous dietary methods.

Explanatory Models of Obesity

   Why are some people obese?

Set-Point Model- weight regulated by a preset internal standard • studies on experimental starvation and dieting are consistent with this.  Metabolism changes to counter extreme changes Problems-  why may some people’s set-point be at “obesity” • twin studies suggest genetics are a component (more so for women apparently)    People can/do become obese from overeating Why has obesity increased drastically in recent years a “set point” not consistent with evolutionary theory

Explanatory Models of Obesity

 Positive Incentive Model- the positive reinforcers of eating have important consequences for weight maintenance    people learn to regulate their eating Power of incentive varies with   personal pleasure in eating social context  biological factors Explain variability in obesity   food abundance/availability/ & VARIETY (research) advertising programs

Obesity & Health

(See research summary 15.4)      Complex question: Is obesity in and of itself, bad for one’s health    moderately overweight-- probably not severely (morbid obesity BMI=40+)-- definitely healthiest BMI’s are around 27 The U-Shaped Relationship for weight & health for all cause mortality.

• Relationship between weight and CVD risk tends to disappear after 65 years (why do you think?) Yo-Yo dieting/Weight Cycling/Weight Loss >20 lbs • more predictive of mortality (even if weight loss intentional, why do you think?) Weight Distribution- Apple (2.3X risk) & Pears Is dieting healthy? Look above!! Some gain actually may be healthy! (Andres, 1995)

Getting Fatter and Dieting More in the USA

 Why are more people gaining weight than ever?

• research shows people are less active than ever (CATV,videos etc) & more likely to eat fast food than ever. (Jeffrey & French,1998) • reduced fat intake (?) but this savings has been exchanged for marked increase in simple sugars.

 Dieting has become big business in a fatter USA • we are highly weight conscious • 1960’s- 10% of adults overweight were dieting • 2000- between 50-70% of adults are/have moderated dietary behavior even for those not morbidly obese • 70% of high school girls; 20% of boys

Losing Weight

 1. Restricting type and amount of intake  smaller portions, different types of food • Low Carb- High Fat and Protein  Sugar Busters and Atkins’s Diet  potentially dangerous diet not based on many experts claim is based on inaccurate readings of literature.

• High Carb- Very Low Fat (15% or less)  Ornish Diet and many vegetarian diets  difficult and extreme diet leaving little room for “fudging”  good evidence that it reverses atherosclerotic deposits • Liquid diets  nutritionally balanced, but very boring! Often administered typically in hospital settings for morbidly obese (VLCD)

Losing Weight

   2. Changing Eating Behaviors   Behavior modification approaches- eating and craving diaries kept, table behaviors (slow down, leave food, chew etc.), awareness training of what and when certain foods are eaten.

reinforcement of good eating habits, not weight change!

3. Exercise  speeds up metabolism, counters metabolic slowdown during dieting; alters distribution of fat independently.

4. Drastic Methods lipo, drugs, stomach surgery, VLCD

Success and Failure in Dieting

 Maintaining weight loss is very difficult but odds are improved with:  formal programs with post treatment programs • include social support, exercise outlets, continued therapist contact • Perri et al, 1988  17% non- post treatment maintained  67% post treatment maintained  self-efficacy  Obese children who lose weight are more likely to keep it off