Chapter 8 and Lecture 6: Diet, exercise, and obesity

The Obesity Epidemic

Since the mid-late 20th century, obesity has increased significantly (in North America and around the world)

Weight concerns prevalence

• Start in childhood and adolescence.

• Overweight ppl are often judged negatively by society.

• Overweight in teens (esp girls) at risk for depression and anxiety disorders.

• Girls' self-esteem related to weight typically declines sharply and consistently from ages 10 to 16.

• The desirability of weight is judged by attractiveness and healthfulness.

• Individuals who stay within certain weight ranges have lower rates of chronic illness and longer lifespans.

Obesity

• Having a very high amount of body fat in relation to lean body mass, or BMI 30 or higher. (Overweight is 25 or higher)

• Declared a disease by the AMA in 2013 and by the CMA in 2015 (to help them gain access to treatment)

Body Mass Index (BMI)

A measure of an adult’s weight in relation to their height; specifically the adult’s weight in kilograms divided by the square of their height in metres (BMI = kg / m²)

• Inaccuracy in defining “healthy/unhealthy” cuz it doesn’t directly measure the amount of body fat

• Doesn’t work for ppl who are rlly tall or rlly short

Obesity trends among US adults

• 42% of American adults were obese, 73% overweight (10-19% older than 90)

• No diff by sex or age

• So many Mcdonalds

Obesity trends in Canada

• Similar trends (but not as severe) as US

• 65%: 35% overweight, 30% obese (In 1978, 14% of Canadian adults were obese)

• Rates of obesity highest between 55 and 64 years

• Obese/overweight high across country. Highest in men: Newfoundland and Labrador. Highest in women: Nunavut

Weight gain occurs when

• Calorie intake > energy spent

• Excess calories are stored as fat in adipose tissue → increases in number if fat cell size becomes excessive

Reasons for adult weight gain

• Accumulation of unlost weight from life events (e.g., holidays, pregnancy).

• Decline in physical activity and metabolism with age

Metabolism

Fat tissue is less metabolically active than lean tissue, which contributes to continued weight gain in overweight individuals even without increased caloric intake.

Heredity/Genetics

• Twin and adoption studies show a consistent genetic link in obesity.

• Specific genes like FTO (satiation) and MC4R (fat preference) are linked to obesity.

• Heredity is not destiny: Physical activity may overcome a genetic predisposition to be overweight (e.g., active people with the FTO gene were no heavier than others)

Set-Point Theory

The body has a "set" weight it strives to maintain via a thermostat-like mechanism in the hypothalamus. This explains why people often return to their original weight after dieting

Hormonal Regulation (Hypothalamus) (3)

• Ghrelin: Signals hunger when the stomach is empty or energy intake is low; levels increase with stress

• Leptin: Regulates eating and metabolism based on the amount of body fat

• Insulin: Regulates blood sugar and fat storage; high levels (hyperinsulinemia) in obese people increase hunger and food consumption

Fat cells

• The number of fat cells increases mainly in childhood and adolescence.

• Fat-cell hyperplasia (too many fat cells) can doom individuals to struggle against a high set-point.

• When fat cells shrink during weight loss, the body responds with metabolic signals similar to starvation (increased hunger, decreased metabolism) to maintain fat stores

Central adiposity

Fat collected in the abdominal region ("rounded in the middle"), is associated with higher rates of hypertension, diabetes, and coronary heart disease compared to fat stored on the thighs, hips, and buttocks

Psychosocial factors in weight control

• Emotion and Eating: Negative emotions (like stress or boredom) can induce eating.

• Ghrelin levels (hunger hormone) increase with stress

• Cultural thing (like US), or weight gain in socially contagious (immigrate to US → eat more), larger portion makes you eat more

• Comfort Foods: Foods eaten during stress tend to be sweet and high in fat.

• Risk Factors: Chronic stress or depression increases the risk for binge eating and subsequent obesity.

• Binge Eating: Is a common feature of individuals seeking treatment for obesity

Childhood Obesity and Prevention

Childhood obesity is a powerful predictor of adult obesity. (An obese infant = 15% chance of becoming an obese adult, an obese 10-13-year-old = 70% chance

Prevention: Preventing obesity must begin early. Parents play a crucial role by modeling and encouraging healthy eating and activity, restricting TV, avoiding food rewards, and providing healthy breakfasts

Childhood obesity Interventions (not effective & effective)

• Not effective: School nutrition programs

• More effective approaches: Comprehensive efforts to improve diets and physical activity, involving school cafeterias, staff, and parental cooperation. 

  • Societal policies, such as mandating calorie labels on restaurant menus, can also encourage healthier choices.

A Systems Approach

• Obesity is an end result of the intricate interactions of biology, behavior, and environment

• The obesity epidemic is driven largely by environmental & lifestyle factors rather than biological ones (stressful lifestyle, high energy/fat food)

• Obesity is heritable. But in most cases of genetic predisposition, risk of obesity is increased by 20-30%

Healthwashing

No regulation of the ingredient when the packaging say “natural”

The Health Halo Effect

The tendency to judge an entire food item as healthier based on one or more narrow attributes that are perceived as healthy.

Food is considered healthier when…

• It is labeled “low-calorie”, “organic”, or “all-natural” 

• It comes from a restaurant seen as healthier (e.g., Subway)

Community-level factors associated with higher risk of obesity...

• lower SES

• lower percentage of college/university graduates

• fewer grocery stores and farmers’ markets

• low satisfaction with safety and public transportation

• reduced accessibility to sports facilities

Behaviours implicated in obesity across the lifespan

• unhealthy diet

• physical inactivity

• poor sleep

• screen time

• stress (cortisol)

• interpersonal factors

What diet is the best

Sustainable, balanced diets that provide optimal amounts of all essential nutrients for the body’s metabolic needs

Problematic diet

• Fad or “crash” diets (premature death and lower level of serotonin for ppl on low carbs diet)

• Added/processed sugar appears to be more predictive of both poor health and obesity than most dietary fat

Does non-celiac gluten sensitivity exist?

2011 study: non-celiac gluten sensitivity “may exist” (ppl who believe they have sensitivity to gluten might become actually sensitive)

2013 study: There’s no such effects

2018 study: Fructans induce symptoms of gluten sensitivity not gluten

Long-term gluten consumption in adults without celiac disease (allergic to gluten) and risk of coronary heart disease

The promotion of gluten-free diets among ppl without celiac disease should not be encouraged

• Avoiding whole grains is asso w higher risk of cardiovascular disease

• This diet population is driven by “health halo effect”

Lifestyle Interventions

Programs, based on behavioral and cognitive methods, are highly effective.

• Nutrition and exercise counseling.

• Self-monitoring: Keeping records of food intake and body weight.

• Managing environmental cues (e.g., shopping with a list).

• Chewing food thoroughly.

•  Behavioural contracting: Setting up rewards for sticking to the diet.

• Social support.

Cognitive methods for diet control

• Motivational interviewing

• Problem-solving training

Medically supervised methods for obesity

• Self-help group

• Medication: Orlistat reduces intestinal absorption of fat

• Bariatric surgery: for severely obese (BMI 35 or higher w significant medical condition) 

  • Effective in reducing weight, cardiovascular events and mortality!

  • Liposuction is a cosmetic procedure, not a weight loss method

Effective methods to prevent relapse

• Only the minority who lose 5% of weight succeed in maintaining weight after for years

• Frequent therapist contact

• Ongoing problem-solving training

• Permanent low-calorie diet

• Consistent exercise

• Good social support

The “Health At Every Size” Approach

An alternative to the weight-centered/weight control approach; focuses on weight-neutral outcomes (e.g., healthy behaviours)

• Goals: Promote size acceptance, end weight discrimination, and reduce the cultural obsession with weight loss and thinness. 

• Some evidence of effectiveness

A factor in both weight gain and poor health; stigma predicts mortality

• Numerous mechanisms, including increased stress & poor coping.

• Weight stigma and anti-fat bias in health care also lead to poorer treatment and inadequate care for patients with obesity.

• Internalization of weight biases interfere with weight management interventions 

The solution: We need to change the attitudes and behaviours of those who stigmatize

Sedentary behaviour

Any activity involving sitting, reclining, or lying down that has a very low energy expenditure. (Bed-rotting)

• May be a distinct risk factor for premature death and adverse health independent of low physical activity (they are measured differently).

  • Mortality is predicted by sedentary behavior itself, this measure doesn’t include low physical exercise

  • In other words, being highly physically active doesn’t mean you will have low sedentary behavior (sitting, lying down)

  • Associated with risk of depression (associated w smth like staying at home

Sedentary behavior and studies

• High metabolic, cardiovascular, diabetes if high sedentary behavior

• Study: Have ppl do more of unsedentary behav just 3 mins more a day (standing, walking) → greatly reduce these health risks!

• Watching TV for an hour lifespan by 22 mins (on avg), whereas smokers shorten their lives by 11 mins on avg per cig

• Premature death and adverse health independent of low physical activity

• Depression risk

How much exercise do you need?

• Adults should get at least 2.5 hrs of more than moderate physical activity each week

• Ppl are more likely to be successful w any exercise program by making physical activity a permanent part of their lifestyle

Health behavior of lower SES, indigenous ppl, and other minorities

• Lower rates of health enhancing behavior

• Poorer health habits (high smoking, alcohol, obesity, low exercise, healthy eating)

• Poorer knowledge about risk factors for disease; living in environments that do not encourage healthy behaviours; barriers to accessing health services; etc.

Eating disorders

• Anorexia Nervosa: Not eating, distorted body image, high mortality

• Bulimia Nervosa: Cycle of binge eating and purging to prevent weight gain

• Affect 2% of popul in western. 90% is female

• Psychological traits: Perfectionism, cultural factors (media-driven ideal female body)

Benefits of exercise

• Psychosocial benefits: Lower stress and anxiety, improve cognitive processes and self-concept

• Physical benefits: Slow down the natural decline in flexibility, strength, cardiovascular function. Protection against premature death and other diseases

Cardiovascular benefits from exercising

• BP: Lower systolic and diastolic BP, and less risk of hypertension

• Lipids and inflammation: Improve serum lipid levels – rasing HDL (good cholesterol) and lowering LDL (bad one) and triglycerides, and reduce inflammation

• Reactivity to stress: Lower HR and BP reactivity to stress

Barriers to exercise

• Lack of time, environment (weather, no convenient place), personal (stress, fatigue, low self-efficacy), and low income & education

• Activity declines sharply from adolescence to early adulthood

Key Strategies for Promoting Exercise

• Pre-assessment: Determine purposes, benefits, and health status before starting.

• Exercise Selection: Tailor exercises to needs and interests.

• Determine where and when to exercise. Make it safe and convenient.

• Specific, measurable goals in a behavioural contract.

• Use reinforcement, both tangible (early on) and intrinsic (enjoyment, physical benefits).

• Exercise with a partner or in a group

• Record Keeping (enhance motivation)

• Interventions are most effective when they are tailored specific to indv