Nutrition and Appetite Regulation

Energy Balance

• 1 kg = 2.2 lbs
• 1 gram of fat = 9 kcal
• 1 lb = 454 grams
• 454g x 9 kcal = 4086 kcal
• Fat cells (adipocytes) contain more than just fat; 87% fat.
• 1 lb body fat = 3500 kcal
• Other constituents: water, protein (hormones)

Weight Loss

• To lose one pound/week:
  • Eat 500 kcal less every day
  • Exercise to use up 500 kcal every day
• Or
  • Combination of diet (less 250 kcal) and exercise (burn 250 kcal): 500 kcal x 7 days = 3500 kcal/week
• Safe weight loss: 1-2 lbs/week (0.5-1.0 kg/week)
• 10% of body weight in 6 months
• Amount of weight loss depends on body weight

Energy Balance Definition

• Weight is a balance between energy consumed and energy expended.
• Energy In = Energy Out, maintains body weight.

Measuring Energy in Foods: Bomb Calorimeter

• Instrument used to determine energy (kcal) content of food.
• Measures heat energy released when a dried food is combusted.
• Energy released in form of heat when bonds break (H2O and CO2 released).
• Amount of heat given off = direct measure of food's energy value.
• kcal = units of heat energy.

Food Intake Definitions

• Appetite: Sensations of hunger, satiation, and satiety that prompt eating or not eating.
• Hunger: Physiological response to a need for food, primarily from chemical messengers in the hypothalamus.
• Satiation: Feeling of satisfaction and fullness during a meal, determining how much food is consumed.
• Satiety: Feeling of satisfaction and fullness after eating, determining how much time passes between meals.

Energy Out: Determination of Daily Caloric Needs

• Daily caloric needs are determined by basal metabolism, thermic effect of food, and activity.
• Sedentary person (1800 kcal/day)
• Physically active person (2200 kcal/day)

Basal Metabolic Rate (BMR)

• Energy required for essential physiological functions under resting conditions.
• Measured after 12 hours without food or exercise.
• Males: 24 x body weight (kg)
• Females: 23 x body weight (kg)
• BMR decreases by 2-5% per decade after growth stops.
• Exercise increases BMR, elevated for about 30 minutes after, or several hours depending intensity

Resting Metabolic Rate (RMR)

• Energy required for normal daily sedentary activities (walking, sitting, standing).
• Approximately 30% above BMR.

Factors Affecting BMR/RMR

• Increasing body temp (fever)
• Environmental temperature (heat, cold)
• Stress (epinephrine)
• Body composition (FFM - muscle, fat mass - body fat)
• Body surface area (increase in height, increasing body weight)
• Physical activity
• Herbal supplements (ephedrine)
• Thyroxin production (T4) released from thyroid gland
• Hormones (leptin)
• Nicotine, caffeine
• Growth (children, pregnancy)
• Aging
• Fasting, low kcal diets, starvation

Thermic Effect of Food (TEF) or Diet Induced Thermogenesis

• Energy needed to digest, absorb, transport, metabolize, and store nutrients.
• This increases energy expenditure, causing body temperature to rise slightly for several hours after eating.
• TEF reaches maximum within one hour after a meal.
• TEF varies depending on food quantity and type.
• Average TEF = 10%

Exercise Metabolic Rate (EMR)

• kcal required for physical activity.
• Many methods to calculate energy expenditure during exercise.

Intensity of Different Activities

• Activities of daily living, moderate, vigorous activities. (Examples provided for each group )

Calculating kcal Expended during Exercise

• (Table of activities, kcal/lb/min, and calories per minute at different body weights.)

Estimating Energy Requirements (EER) Formulas

• Males (19 and older): EER = 662 - 9.53 x age + PA x [(15.91 x wt) + (539.6 x ht)]
• Females (19 and older): EER = 354 - 6.91 x age + PA x [(9.36 x wt) + (726 x ht)]

EER Physical Activity Factors

(Values provided in a table according to age and sex). Sedentary, low active, active, very active.

Calculating the EER for a specific individual (example provided)

Defining a Healthy Body Weight:

• Height/Weight Tables
• BMI
• % body fat
• Body shape
• Body fat distribution
• Waist hip ratio
• Waist circumference

Body Mass Index (BMI): WHO Classification

• Underweight (<18.5 kg/m²)
• Normal Range (18.5-24.9 kg/m²)
• Overweight/pre-obese (25.0-29.9 kg/m²)
• Class I Obesity (30.0-34.9 kg/m²)
• Class II Obesity (35.0-39.9 kg/m²)
• Class III Obesity (≥40 kg/m²)

BMI and Mortality

• Graph showing correlation between BMI and mortality risk

Calculating BMI (example provided)

Determining BMI (example provided)

Determining Body Fat Methods

• Fat fold measures
• Hydro densitometry
• Bioelectrical impedance
• Air Displacement plethysmography
• Dual energy X-ray absorptiometry (DEXA)
• MRI

Body Shape: Body Fat Distribution

• Subcutaneous fat, intra-abdominal fat (visceral fat), intramuscular fat, Intramyocellular lipids (IMCL)
• Extramyocellular lipids (EMCL)

Body Shape: Apple and Pear

• Apple obesity (Android): abdominal fat
• Pear obesity (Gynoid): lower body fat
• Obesity: waist girth (values for men and women provided)

Location of Body Fat

• Visceral Fat (abdominal fat), subcutaneous fat

Weight Management

• Overweight/obesity
• Underweight

Overweight and Obese (BMI) Canadian Adults (2021) Statistics

(Graph showing statistics, percentages)

Health Problems Associated with Obesity

• Cardiovascular disease
• Metabolic syndrome
• Type 2 diabetes
• Cancers (colon, breast, endometrial)
• Gout
• Gallbladder disease
• Sleep apnea and respiratory problems
• Bone and joint problems

Health Risks Associated with Excess Body Weight

• General increase in risk for many diseases (blood pressure, LDL, triglycerides, HDL, type 2 diabetes).

Causes of Obesity

• Energy in > Energy out
  • Fat cell development
  • Increase in kcal
  • Portion sizes
  • Inactivity
  • TV watching
  • Fat cell metabolism (thyroid function, LPL)
  • Set point theory
  • Genetics (leptin, ghrelin, adiponectin)

Fat Cell Development

• Hyperplastic obesity (increase in number of fat cells)
• Hypertrophic obesity (increase in size of fat cells) (Diagram explaining fat cell development from growth)

Other Possible Causes of Obesity

• BMI increase over years
• Energy intake has also been increasing
• Physical Activity hasn't changed

Lifestyle and Rising Obesity Rates

(Graph showing percentages of increase for soft drinks, french fries, and cheeseburgers)

Regardless of Hunger

• People typically overeat when there's abundance and variety.

Fat Cell Metabolism: Thyroid Function

• Thyroid gland produces hormones (T4 - thyroxin, T3 - triiodothyronine)
• Increases metabolism
• Regulates protein, fat, and CHO catabolism

Fat Cell Metabolism: LPL

• Lipoprotein lipase is an enzyme on fat cells promoting fat storage in fat and muscle cells.
• Takes triglycerides from passing lipoproteins, hydrolyzes them, and passes fatty acids into the cell.
• People with high LPL activity are good at storing fat.
• Obese people have higher LPL activity than lean people.
• LPL activity is regulated by sex hormones (higher in women). (location of fat)

LPL - Research Findings

• LPL levels increased during weight loss.
• Weight loss signals increase LPL activity/production.
• May explain why obese people regain weight after loss.

Set Point Theory

• Body maintains a set weight through internal controls that adjust metabolism. (Graph explaining concept)

Obesity Causes: Genetics

• 2 parents obese = 80% chance child becomes obese
• 1 parent obese = 50% chance child becomes obese

Obesity Causes: Genetics - Leptin

• Acts as an "anti-obesity" hormone.
• A protein produced by fat cells, affecting the hypothalamus.
• Leptin amount is proportional to fat stores (more fat = more leptin).

Causes of Obesity - Leptin (Mechanism of Action)

• Leptin affects food intake and energy expenditure by binding to leptin receptors in the hypothalamus.
• Leptin inhibits hypothalamus peptides like neuropeptide Y (NPY increases appetite).

Leptin Resistance

• Obese people may have high leptin levels but their energy balance doesn't shift negatively.

Mice Without and With Leptin (Experiment)

• Mice with defective ob gene don't produce leptin = become obese.
• Mice receiving leptin injections lose weight

Obesity: Gut Peptides

• Many gut peptides regulate food intake.
• Cholecystokinin (CCK), Peptide tyrosine tyrosine (PYY), Ghrelin, Glucagon-like peptide-1 (GLP-1)

Obesity: Gut Peptides - CCK

• Dietary protein/fat in small intestine stimulate CCK release.
• CCK binds to receptors, signaling hypothalamus to reduce food intake.

Obesity: Gut Peptides - PYY

• Released by the small intestine after eating, suppressing food intake & appetite

Obesity: Gut Peptides - Ghrelin

• Stimulates food intake.
• Produced by stomach cells, stimulates growth hormone release, and increases hunger.

Obesity: Gut Peptides - Ghrelin (Blood Concentration)

(Diagram showing blood ghrelin concentration over 24 hours, lowest after meals)

Obesity: Gut Peptides - Ghrelin (Clinical Application)

• Dieters who lose weight and resume normal eating often produce more ghrelin, counteracting weight loss efforts.
• Obese people with gastric bypass surgery often have very little ghrelin.

Obesity: Gut Peptides - GLP-1 (Glucagon-Like Peptide-1)

• Gut hormone activating GLP-1 receptors in pancreas, affecting glucagon/insulin release for blood glucose control

Obesity Treatment and Prevention

• Diet and Exercise
• Drug therapy
• Surgery

Best for Weight Loss & Maintenance

• Diet and increase physical activity (reducing Energy In and increasing Energy Out).

Obesity Treatment: Drug Therapy - Semaglutide

• GLP-1 receptor agonist
• Approved for type 2 diabetes and weight loss
• Increases insulin, decreases glucagon.
• Slows gastric emptying, reducing appetite. Injection under skin

Obesity Treatment: Drug Therapy - Semaglutide Considerations

• Health Canada approved Wegovy, but not Ozempic for weight loss.
• Physicians may prescribe either.
• Approximate cost = $400/month
• Side Effects: nausea, vomiting, heartburn, constipation, dizziness, fatigue

Gastric Surgery (Bariatric Surgery)

• Adjustable Gastric Band Procedure
• Roux-en-Y Type of Gastric Bypass Procedure

Weight Loss Strategies

• Watch serving sizes
• Reduce high-calorie foods (fat, sugar)
• Don’t get too hungry (eat breakfast, increase fiber, veggies)
• Engage in more physical activity if appetite increases

Diets, Diets Everywhere

• Tips for differentiating fad/healthy diets while assessing weight loss efficacy (diet type planning, advantages and disadvantages).

Evaluating Weight-Loss Programs

• Healthy vs. fad diets (criteria for distinguishing).

Health Risks of Underweight

• Inability to preserve lean tissue during illness
• Associated with osteoporosis and bone fractures.
• Underweight females may have irregular menstrual cycles (amenorrhea), and/or difficulty conceiving.
• Linked to poor-quality pregnancies and/or unhealthy babies

Eating Disorders

• Anorexia Nervosa (distorted body image, amenorrhea, starvation)
• Bulimia Nervosa (binge-purge cycle, over or normal weight )
• Binge-Eating Disorder (BED; overconsumption without purging may be overweight or obese)
• Eating Disorder Not Otherwise Specified (EDNOS)