Obesity Part 1 Flashcards
What causes obesity?
Obesity results from long standing imbalance between
- energy intake &
energy expenditure
What are the types of obesity?
- Primary Obesity: due to caloric imbalance.
* Secondary Obesity: due to medical disorder like Cushing’s syndrome.
What is BMI?
• Body mass index (BMI)
• A Measure of weight relative to height
• Strongly correlates with total fat content in adults • Some exceptions
=Weight (kg) /Height (m2)
- Obesity: individual has a body mass index (BMI) ≥ 30 kg/m2
- Obesity in the United States is projected to increase from 99 million in 2008 to 164 million individuals by 2030
What are the main weight ranges of BMI?
▪Usually used for adults
▪Healthy range=18.5 - 24.9
▪Overweight range= 25 - 29.9
▪Obese ≥ 30
How is obesity diagnosed?
• Appearance - visual • BMI calculation
• Waist circumference: ≥ 40 inches for men
≥ 35 inches in women
• Waist to hip ratio (WHR): ≥ 0.9 for men
≥ 0.8 for women
❖In both men and women a WHR of ≥ 1 increases health risks
What are the effects of obesity?
Metabolic effects
• Dyslipidimia
• Glucose Intolerance
• Insulin Resistance
Increased risk of: • Atherosclerosis, • Cardiovascular disease • Stroke, • Diabetes, • Cancer
Describe adipocyte fat composition
-TAGs constitute nearly 90% of adipocyte mass
- Modest weight gain results in an increase in adipocyte size (hypertrophy)
- Excessive weight gain (obesity) results in increases in both size (hypertrophy) and number (hyperplasia) of adipocytes
Describe body fat distribution
• Two kinds of fats based on location:
➢Visceral and
➢Subcutaneous
- Visceral and abdominal fat (F.A.) and cytokines are released into the portal vein, are taken up by the liver and can contribute to higher VLDL in the blood.
- Fat (F.A.) released from subcutaneous fat enters general circulation and is used up by muscle prior to reaching the liver
How is body fat located for the important in risk asssessment of obesity?
-Higher adipose tissue: muscle
ratio & higher amount of visceral fat
-Higher risk of coronary heart disease and development of features of Syndrome X/ Metabolic syndrome
What methods are used to assess body fat content?
- Skin fold measurements: Used to assess subcutaneous fat by comparing it to population standards
- Bioelectric impedance : Measures conduction speed of a small electric current in the body
- Underwater weighing
Describe body fat content
• As BMI increases from 20 to 30, the body’s TAG content doubles
• Dietary fat is 90 % TAG •Chylomicrons are
about 85% TAG
• Adipocytes are about
90 % TAG
Explain fat storage and hormone function
- In addition to providing a depot for TAG’s (energy), adipocytes secrete several hormones that play a role in:
- appetite control/weight gain (leptin-appetite suppressant)
- Inflammation (cytokines & adiponectin) and
- insulin resistance (adiponectin)
What are the factors contributing to obesity?
- Hypothesis I : A biologically predetermined “Set point” for body weight for most individuals or
- Hypothesis II: A “Settling point” that reflects food intake, energy expenditure and other factors
Major factors that regulate body weight
• Genetic
• Environmental (lifestyle/behavioral)
What role does genetics playy in obesity?
- Multiple genetic factors
- Genes set the stage,
• However, body weight
determined by:
– Diet &
– Level of exercise
Mutations may result in hyperphagia and massive obesity
•Leptin gene or
•its receptor
What are the long term signals of adipose tissue?
Long Term Signals
• Leptin is produced proportionally to fat cell
density and through its action on the
hypothalamus:
- plays a key role in weight gain,
- appetite suppression and
- energy expenditure
• Leptin also regulates inflammatory responses,
blood pressure and bone density
• Insulin: Similar to leptin, dampens appetite by exerting its effects on the hypothalamus
