Week 2- Obesity Flashcards
how to measure BMI
weight (kg) divided by height (m) sqaured
what is the 3 BMI classes for obesity
Obesity ≥ 30 kg/m2
- Class I 30 - 34.9
- Class II 35 - 39.9
- Class III 40+
what is a obese BMI
Obesity ≥ 30 kg/m2
what are the limitations of BMI
- correlates with excess adipose tissue but does not reflect body composition
- does not differentiate between fat mass and fat-free mass
- does not account for body fat distribution
- limited applicability to certain populations including: young adults, athletes, older adults (over 65 years), pregnant females, and certain racial/ethnic groups (Asian, Black and Canadian First Nations, including Inuit)
- e.g. Japan uses > 25 kg/m2 as the cut-off for obesity
waist circumference measures?
index of central adiposity (abdominal obesity)
what is an obese waist circumference in female and male
female > 35 inches/ 88cm
male > 40 inches/ 102cm
where to measure waist circumference
approximate midpoint between the lowest rib and the top of the iliac crest
what has a higher LR+; BMI or waist circumference
BMI
waist to hip ratio
- waist measurement (same as waist circumference) divided by hip measurement taken around the widest portion of the buttocks
what is waist to hi[ ratio for
assess body fat distribution
what is an obese waist to hip ratio for males and females
male >1
female >0.85
dual energy x ray absorptiometry (DXA) strengths and limitations
precise
expensive, radiation, limited use BMI >35
bioelectric impedance (BIA) strengths and limitations
convenient, portable, inexpensive, accurate for lean body mass
accuracy reduced by poor hydration status, under-estimates fat mass in overweight and obese people
skinfold thickness strengths and limitations
convenient, portable, inexpensive
hard to calibrate, not as accurate or reproducible
what is the gold standard for body fat assessment, used to establish accuracy of BMI?
Obesity, BF% or BMI (dual energy x- ray absorptiometry, DXA)
gold standard for BF%, obesity, BMI
DXA
what physical exams to assess for obesity
- BMI (height + weight)
- degree and distribution of body fat (e.g. waist circumference)
- overall nutritional status
- blood pressure
- other relevant physical exams to assess secondary causes of weight gain
what labs for obesity?
all patients should be screened for comorbid conditions, including: fasting glucose, hemoglobin A1c (HbA1c), lipid panel, and comprehensive metabolic profile (i.e. electrolytes, kidney function, liver function, calcium, glucose)
how many adult Canadians are obese
1 in 3
medical history to consider in obesity
- the age at onset of weight gain
- recent weight changes (watch for rapid weight gain)
- family history of obesity
- occupational history
- eating and exercise behavior
- previous weight loss experience
- psychosocial factors, including assessment for mood and eating disorders
knowing this information will help differentiate between primary and secondary weight gain
what is primary weight gain
accumulate adipose tissue from imbalance of caloric intake and energy expenditure
what age and gender is primary weight gain more common for
F > M
24-34 years old
adults after 55 years tend to lose weight
primary weight gain formula
increase caloric intake, appetite
decreased physical activity level, basal metabolic rate (BMR) and thermic effect of food
environmental factors contributing weight gain
increased caloric intake (processed), eating patterns (binging), alcohol (liquid calories), insufficient sleep, smoking cessation, sedentary lifestyle, physical disability, obesogenic environment, society (SES), culture, environmental chemicals (endocrine disrupting)
abnormalities in brain gut axis in obesity
-satiety decreased (PYY decrease)
- increases gastric emptying and volume
-pscyhological (depression and anxiety)
what is secondary weight gain?
accumulation of adipose tissue from genetics, medical conditions (i.e. neuroendocrine disorders) or medication side effects
–>secondary causes can co exist with primary obesity
genetic contribution to secondary weight gain
-multiple genes (polygenic)
–>i.e - Prader-Willi syndrome, Laurence-Moon syndrome, Cohen syndrome, and
Biemond syndrome
genes affect leptin/melanocortin pathway
genetic influence % of obesity and what on
90% inter-individual variation
total body fat, fat-free mass, body fat distribution, basal
metabolic rate, physical activity, macronutrient intake and eating behavior
Cushing’s syndrome (endocrine disorder associated with weight gain)
hypercortisolism (high cortisol) alters metabolism causing visceral adiposity and insulin resistance (T2D cormorbid)
hyperinsulinemia (endocrine disorder associated with weight gain)
elevated insulin; insulin resistance preceding T2D