Health Psychology Chapter 15: Eating & Dieting

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

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 4 kcals/gram • Fats 9 kcals/gram • Alcohol 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 /m2-- 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

Health Psychology Chapter 15: Eating & Dieting