Week 9 Flashcards
Ways to assess body composition (top = best/expensive)
Magnetic resonance imaging (MRI)
Dual-energy X-ray absorptiometry (DEXA)
Underwater weighing
Sum of skin folds
Waist circumference
Waist/hip ratio
BMI
Bioelectrical impedance
What is obesity/overweight associated with ?
higher mortality rate
^ risk of CVD,
^ risk of diabetes,
^ risk of hypertension
^ risk of stroke
^ risk of cancer
How our environment has become more obesogenic?
Abundance of high-calorie foods
Reduced physical activity
Sedentary jobs
Increased screen time
Reliance on cars and tech
Mechanisms/Causes that contribute to Insulin Resistance in Obese Individuals?
Chronic Inflammation: Excess fat tissue releases inflammatory cytokines, disrupting insulin signaling.
Altered Adipokines: Increased leptin (leading to leptin resistance) and decreased adiponectin impair glucose metabolism.
Ectopic Fat Accumulation: Fat buildup in non-adipose tissues (such as liver and muscle) interferes with insulin signaling
Effect of Obesity on Lipoprotein Profiles?
Higher levels of LDL (bad cholesterol) and triglycerides.
Lower levels of HDL (good cholesterol), increasing CVD risk
Impact of Weight-Loss Strategies on Adipokine Profiles?
Weight loss improves adipokine balance by:
Increasing adiponectin, which is anti-inflammatory and enhances insulin sensitivity.
Reducing leptin and pro-inflammatory cytokines, leading to improved metabolic health.
Is Adipose Tissue Passive or Active? Role?
Adipose tissue is an active endocrine organ.
Beyond storing fat, it secretes adipokines like leptin and adiponectin, which regulate appetite, metabolism, and inflammation, playing a key role in energy balance and metabolic health.
Insulin and Glut4 transporters?
Insulin regulates glucose uptake by triggering GLUT4 transporters in muscle and fat cells to move to the cell membrane, allowing glucose entry.
In insulin resistance, this process is impaired, leading to high blood sugar levels and encouragement of fat storage
Insulin and lipid storage/transport in insulin resistance?
In adipocytes, insulin promotes fat storage by activating LPL (Lipoprotein Lipase), which facilitates triglyceride uptake, and inhibiting HSL (Hormone Sensitive Lipase), which prevents fat breakdown.
In insulin resistance, triglyceride (TG) clearance decreases, and free fatty acid (FFA) release increases, particularly after meals. This disrupts normal fat storage, contributing to metabolic issues like increased fat accumulation and insulin dysfunction.
Energy Balance?
If energy intake exceeds expenditure, weight is gained; if intake is less than expenditure, weight is lost.
Physical activity =15-30%
Thermic effect an feeding = 10-15%
BMR - 60-75%
Diet vs. Exercise for weight loss?
Diet leads to greater initial weight loss, but exercise is crucial for long-term success
Exercise helps maintain muscle mass and protects BMR during weight loss
Both stimulate mitochondrial biogenesis, but exercise is key for maintaining T3 levels and metabolic rate.
Exercise improves cardiovascular risk factors (like lipoprotein profile, blood pressure), while diet alone is less effective.
Long-term success requires a combination of approaches tailored to individual needs, with continuous support for sustainable lifestyle changes
Appetite regulation Endocrinology?
Leptin: Produced by adipose tissue, it signals satiety. Weight loss decreases leptin levels, increasing appetite.
Ghrelin: The “hunger hormone” increases when energy intake is low, promoting hunger during weight loss.
Insulin: Levels may decrease during weight loss, affecting appetite and fat storage.
Peptide YY (PYY): This hormone, released after eating, decreases appetite. It can be reduced with weight loss, leading to increased hunger.
Importance of BMR and Organ Contributions?
Basal Metabolic Rate (BMR) is the energy required to maintain basic functions at rest, such as breathing and body temperature regulation, accounting for 60-75% of daily energy expenditure. Major contributors to BMR include:
Muscles: Highly active, using significant energy even at rest.
Brain: Uses about 20% of total energy, despite being only 2% of body weight.
Liver: Consumes around 20% of energy for metabolic processes, at rest
Heart: Metabolically active, using about 10% of total energy at rest.
Effect of Diet and Exercise on Body Weight and Composition? TIming of this?
Diet: A calorie deficit leads to weight loss, primarily from fat mass (FM).
However, inadequate protein intake or insufficient exercise can result in muscle mass (FFM) loss as well.
Exercise: Resistance training helps preserve or increase fat-free mass (FFM) while reducing fat mass (FM).
Aerobic exercise aids in fat burning but is less effective in preserving muscle mass compared to resistance training.
Timing:
Short-term (weeks): Initial changes mostly reduce fat mass (FM).
Long-term (months to years): Body composition adjustments include muscle gain or loss, influencing fat-free mass (FFM).
Fat Mass vs Fat-Free Mass? Links to weight loss?
Fat Mass (FM): Refers to the total weight of body fat, which serves as an energy reserve.
Fat-Free Mass (FFM): Includes everything in the body that is not fat (muscles, bones, organs, water), contributing to basal metabolic rate.
Preserving FFM during weight loss is crucial for maintaining metabolic health and functional capacity.
Triiodothyronine (T3) Activity?
T3, the active thyroid hormone, boosts metabolism by increasing energy expenditure and fat oxidation. During weight loss or caloric restriction, T3 levels may drop, lowering the metabolic rate and making further weight loss more difficult. This reduction is a compensatory mechanism to prevent excessive weight loss but can lead to a weight loss plateau.
