Obesity Flashcards
(37 cards)
What 4 things account for energy expenditure?
- basal metabolism
- physical activity
- digestion of food
- non-exercise activity
What is the basal metabolic rate (BMR)?
- rate of O2 consumption by body cells at rest
- indicates the energy used to maintain body processes at rest (body temperature, breathing, circulation, muscle tone, etc.)
What are factors that influence BMR?
- body size (heat loss through body surface)
- body composition (muscle tissue is more metabolicallly active than fat)
- age (BMR decreases with age)
- thyroid hormone levels (increases BMR)
- genetics (determines BMR setpoint)
- other= fever, stimulat drugs, emotions
Describe the energy expenditure with digestion of food.
- energy used to digest, absorb and assimilate food after ingestion
- metabolism increases after eating, then decreases within a few ours
- depends on the amount and type of food
What are some thermogenic foods?
- coconut oil
- apple cider vinegar
- celery
- green tea
- chilli peppers
- cinammon
- garlic
- tumeric
- salmon
These increase metabolism by enhancing thermogenesis
What is non-exercise activity thermogenesis (NEAT)?
The energy expended in activities such as using the stairs, walking the dog, yard work, and fidgeting.
What happens when intake exceeds demands?
- excess nutrients stored as fat = weight gain
- health risk r/t obesity
- possible nutritional toxicities
What happens when intake does not meet demands?
- fat stores and other body tissues are broken down = weight loss
- possible nutritional deficiencies
What is body weight set point?
A set point around which the body maintains an equilibrium body weight
Determined by genetics (including epigenetics) and is influenced by environmental, biological and behavioural factors
When body weight changes, compensatory alterations in energy expenditure return it to set point.
Where in the brain does regulation of hunger occur?
Hypothalamus has hunger and satiety centres.
Receives input from sensory afferents, hormones, the microbiome etc.
Responds by altering appetite (food intake) and energy expenditure
How does satiety occur?
- gastrointestinal stretch (via vagal afferents)
- release of insulin from the pancreas
- release of leptin from adipocytes
- release of GI hormones (e.g. CCK and GLP-1 released by intestinal cells with food entry)
- nutrients (e.g. fats slow gastric emptying and contribute to satiety
How does infection and inflammation decrease appetite?
TNFa, IL-1 and IL-6 released in response to inflammation and infection decrease appetite.
What is leptin?
An adipokine (hormone) secreted by adipocytes.
Acts on hypothalamus to maintain body weight:
1. suppresses hunger and feeding behaviour
2. increases energy expenditure (increased BME, body temp; decreases adipose tissue mass)
Production usually increases with increasing fat cell mass.
How is hunger stimulated?
- release of ghrelin form the stomach when empty to increase appetite
- low blood glucose levels - stimulate glucose sensitive neurons of the hypothalamus to increase appetite
- cortisol stimulates appetite (stress eating)
What happens to Ghrelin levels during fasting?
- increase
- encourages eating and slows down fat metabolism (makes weight loss difficult)
- success of bypass syrgery may be related to reduced ghrelin levels
What is the role of the mesolimbic (hedonic) areas?
involved in the emotional, pleasurable, and rewarding aspects of eating (hedonic eating)
What role does the cognitive (executive functioning) areas of the brain have in eating?
Overrides the hedonic eating and decides what and when to eat (works best when well rested and low stress)
Define obesity.
A complex, progressive, and relapsing chronic disease characterized by excessive body fat that impairs health.
Why is obesity considered to be a chronic disease?
- Complex pathophysiology involving interaction between genes, biological factors, environment and behaviours.
- Outward S&S (assessed as BMI and waist circumference)
- Causes morbidity and mortality (obesity-related health complications)
- Causes abnormal tissue fucntion (dysregulated release of adipokines from adipose tissue and abnormal CNS response to satiety hormones)
What is adipose tissue?
- composed of adipocytes that contain a large lipid droplet
- located under the skin (subcutaneous), around internal organs (visceral) and in bone marrow
- functions to store energy, protect organs, provide insulation, and secrete hormones (adipokines)
- brown adipose tissue generates body heat (non-shivering thermogenesis)
- comprises 20-25% of body weight in a healthy adult
What are adipokines?
Hormones and cytokines released from adipocytes.
involved in:
- regulating food intake, satiety and energy balance
- insulin sensitivity (and insulin resistance)
- lipoprotein metabolism
- inflammation
- adipogenesis
What is subcutaneous fat?
- located under the skin
- generally, equally distributed
- accounts for “pear-shape” when fat accumulates in the hips, thighs and buttoks
- can be adapted through lifestyle factors such as diet and exercise
What is visceral fat?
- surrounds organs and is contained in the omentum (peritoneal fold that covers organs of the abdomen)
- accounts for ‘apple-shape’ when fat accumulates
- contributes to insulin resistance, inflammation, and cardiovascular disease
How is body weight classified?
- body mass index (BMI)
- waist circumference (WC)
