Obesity, BMI and Weight Management

• Obesity has reached epidemic proportions.
• Obesity is caused by a complex range of factors that vary across populations.
• Proper weight management involves a healthy relationship with food and physical activity, as well as psychological and environmental control.
• Short-term solutions to weight issues are rarely effective in the long term, and fad diets are generally not sustainable.

Body Mass Index

• BMI is easy to obtain but does not consider body composition or distribution of weight.
• BMI can still be a useful measure.
• Underweight: BMI < 18.5
• Normal range: BMI 18.5-24.9
• Overweight: BMI ≥ 25.0
• Preobese: BMI 25.0-29.9
• Obese: BMI ≥ 30.0
• Obese class I: BMI 30.0-34.9
• Obese class II: BMI 35.0-39.9
• Obese class III: BMI ≥ 40.0

Obesity in Canada

• Worldwide prevalence of obesity more than doubled between 1980 and 2014.
• Approximately 64% of adults in Canada are overweight or obese (2017).
• Approximately 30% of children aged 5-17 are overweight or obese (2017).
• Approximately 67% of indigenous adults are overweight or obese (2017).
• Many organizations now recognize obesity as a chronic disease.

Prevalence of Self-Reported and Measured Overweight and Obesity among Adults Aged 20 or Older, 2001–2014

• Data obtained by self-report are often lower than actual values.
• People tend to underreport obesity-related attributes rather than overreport.

Risks of Excess Body Fat

• Obesity reduces life expectancy by up to 14 years and causes 1/10 premature adult deaths.
• Obesity is associated with an increased risk of cardiovascular disease (CVD) and diabetes.
• Obesity is associated with an increased risk of many cancers, impaired immune function, diseases of the kidney and gallbladder, bone and joint disorders, impotence, incontinence, pregnancy risks, and psychological disorders.
• There are also risks associated with very low weight.

Types of Body Fat

• Essential fat is 3% of male weight and 12% of female weight and is essential for reproductive capacity.
• Essential fat is hormonally determined and is not associated with health risk.
• "Risky" fat is non-essential and is visceral or subcutaneous adipose tissue, depending on sex, age, diet, and activity.
• "Risky" fat is mobilized by energy demand and is hormonally determined.
• Overweight men tend to have an apple (android) shape.
• Overweight women tend to have a pear (gynoid) shape.

Obesity and Diabetes

• During digestion, carbohydrates are broken down in the small intestine into glucose that enters the bloodstream.
• The presence of glucose signals the pancreas to release insulin, which helps cells take up glucose.
• Once inside a cell, glucose can be converted to energy.
• In diabetes, this process is disrupted, resulting in a buildup of glucose in the bloodstream.
• Type 1 diabetes: the pancreas produces little or no insulin.
• Type 2 diabetes: the pancreas produces too little insulin, or the body's cells are resistant to it.
• Glucose builds up in the bloodstream.
• Symptoms of diabetes include Frequent urination, extreme thirst and hunger, unexplained weight loss, extreme fatigue, blurred vision, frequent infections, slow wound healing, tingling or numbness in hands and feet and dry, itchy skin

Evaluating Body Weight and Composition

• Methods include height-weight charts, hydrostatic weighing, skinfold measurements, circumference measurements, electrical impedance, and scanning (e.g. MRI).
• BMI is the simplest and most broadly applicable.
• BMI = (weight in kilograms) / (height in meters)^2

What determines your weight?

• Energy Balance Equation: energy input - energy output = +ve/-ve energy balance
• Approximately 3500 kcal/lb of fat (but not an exact science).
• Energy in: Food, carbohydrates, lipids, proteins, alcohol.
• Energy out: Basal metabolism (60-75%), thermogenesis (10%), physical activity (15-30%).

Energy expenditure

• Basal (Resting) Metabolic Rate (BMR/RMR) has a rough estimate = 10 x your weight in lbs.
• BMR/RMR is affected by genetics, higher lean (muscle) mass, exercise and physical activity, greater height and weight and male sex, among other factors.
• Energy expenditure is also affected by thermic effect of food and physical activity.
• BMR accounts for 60-65% of energy expenditure.
• Physical activity accounts for 25-35% of energy expenditure.
• Thermic effect of food accounts for 5-10% of energy expenditure.

Energy intake

• Hunger is the physiological need to eat, influenced by 12+ internal signals.
• Appetite is the desire to eat (not always physiological), influenced by sight, smell, and thought of food.
• Satiety is the feeling of fullness (physiological).
• Eating voluminous foods, mixed-nutrient meals, fiber-rich foods, and eating slowly all promote satiety.
• It takes approximately 20 minutes for the brain to receive the message that the stomach is full.
• Eat slowly and in small portions.

Causes of Obesity

• Physical activity levels are declining, beginning in childhood and continuing through life.
• People spend an average of 9.7 hours a day being sedentary.
• The obesogenic environment promotes the overconsumption of calories.
• People living in areas with few grocery stores, lots of fast-food outlets, and few opportunities for physical activity are at an increased risk.
• Psychosocial factors are also a factor, and policy changes are one way to help curb obesity.
• Contributing factors include food consumption (eating too many calories, which increases fat storage), and food production (high-calorie, unhealthy foods are often cheap and accessible; large portion sizes).
• Other factors are physiology (hormonal imbalances, genetics, metabolic problems), individual physical activity (level of PA, ability to exercise), environmental physical activity (promotes PA), individual psychology (depression, anxiety, addiction), and social psychology (friends and family).

Dangers of Obesity

• Stroke
• Heart disease
• Sleep apnea
• Some forms of cancer
• Gallbladder disease
• Type II Diabetes
• Osteoarthritis
• Hypertension
• High blood cholesterol
• Incontinence
• Pregnancy complications
• Menstrual irregularities
• Hirsutism
• Psychological disorders such as depression
• Increased risks during surgery
• Many others

Ideal Weight

• Medical definition: the weight at which one's health risk is lowest.
• Lifestyle should be the guide in determining ideal weight.
• Focus on eating moderate amounts of healthful foods and being physically active instead of focusing on a particular weight.
• Letting a healthy lifestyle determine weight can help avoid unhealthy eating habits and negative body image.

Reinforcing dieting: feedback loop

• Crash diet can lead to weight loss of muscle, water and some fat.
• Weightloss can lead to hormonal, metabolic and psychological changes
• These changes can lead to increased appetite, fat storage and inability to maintain diet.
• All of which lead to weight gain and dissatisfaction.

Guidelines for Sound Weight Control: Sensible Diet

• Goal: Reduce total caloric intake
• Should not be too drastic; minimum of 1,200 kcal/day
• Eat filling and nutrient-dense foods; try to avoid empty calories.
• Protein, fat, and fiber are more filling than foods that are high in simple carbohydrates.
• Eat plenty of fruits and vegetables.
• Calorie tracking may help (journaling, or an app like MyFitnessPal).

Guidelines for Sound Weight Control: Change in Eating Habits

• Goal: Reduce total caloric intake
• Use smaller plates.
• Try to eat slowly.
• Wait a little while before eating more.
• Leave tempting foods out of sight.
• Be conscious of environmental cues that promote consumption.
• Avoid shopping when hungry.
• Avoid mindless eating.

Guidelines for Sound Weight Control: Psychological Modification

• Self-efficacy: belief in one's ability to change
• May need to change relationship with food/PA so they are positive concepts
• Identify triggers, how to cope with situations that may promote overeating
• Challenge negative patterns of thoughts and replace them with healthier ones
• Support is key: Friends/family, groups, networks/blogs or apps (e.g. MyFitnessPal)

Guidelines for Sound Weight Control: Physical Activity

• Goal: Increase caloric expenditure
• Increases basal metabolic rate
• Body becomes more efficient at burning calories
• Helps maintain muscle mass, reduce fat mass
• Helps relieve depression, anxiety
• May help promote self-esteem
• Regularity is key: find activities you enjoy, and people you enjoy doing them with
• Duration is more important than intensity for weight reduction