OBESITY Flashcards
(18 cards)
What is obesity?
Obesity: an excess of body fat (adipose tissue)
Complex, multifactorial condition
Now considered a global epidemic
In most populations, prevalence of overweight & obesity has steadily increased over past 20 yrs in adults, adolescents, & children
Studies from Sub-Saharan countries also report increasing prevalence in urban & rural areas
Aetiology is associated with heterogeneous group of conditions; multiple causes
Etiology of obesity
Genetic factors:
Monogeneic syndromes
Susceptibility genes
Environmental factors:
Metabolic rate
Excercise
Food intake
Culture
What is the Physiology of Obesity
An increase in body fat requires that energy intake be increased over energy expenditure
Alterations in body weight lead to compensatory changes in energy expenditure & energy intake that tend to defend body weight
Regions in the hypothalamus involved in energy homeostasis
regions integrate information about meal size, nutrient composition & adipocyte stores from peripheral & central signals
regulate food intake & energy expenditure through anterior pituitary, descending autonomic pathways & other brain regions
Discuss LEPTIN
LEPTIN:
Made by the adipocytes. It is a circulating protein that helps maintain energy balance
Works primarily within the hypothalamus and exert its effects on peripheral tissues
Major role in body weight regulation: signals satiety to hypothalamus reduces dietary intake & fat storage while modulating energy expenditure & CHO metabolism to prevent further weight gain
Ironically, most humans who are obese have high serum leptin!!
Discuss GHRELIN
Stimulates hunger (orexigenic effect) and GH release (via GH secretagogue receptor).
Produced in the stomach.
Sleep deprivation, fasting, or Prader-Willi syndrome increase Ghrelin production
Acts on lateral area of hypothalamus (hunger center) to increase appetite
Neurotransmitters influence communication between hypothalamus, GIT & adipose tissue:
Melanocortins, Neuropeptide Y, Insulin, Gut Peptides
They modulate energy expenditure
Regulate appetite/ food intake & body weight
Genetic causes of Obesity
Obesity is a feature of at least 24 genetic disorders :
Examples include:
Prader Willi syndrome: genetic abnormality of long arm of chromosome 15 (q11-13)
Neonatal hypotonia, severe hyperphagia, childhood obesity, mental retardation, hypogonadotrophic hypogonadism, short stature, dysmorphic features, cryptorchidism, behavioral problems
Bardet Biedl syndromes –Autosomal recessive disorder
Retinal dystrophy, obesity, dental anomalies, polydactyl, hypogenitalism, mental retardation, HT & renal malformations
Monogenic obesity syndromes
Rare diseases in which various genetic mutations are the primary cause of early onset moderate to severe obesity
Mutations of: leptin gene, leptin receptor gene
marked hyperphagia & severe early-onset obesity in humans
Mutations of: POMC gene, POMC processing enzyme PC1, melanocortin 3 & 4 receptors, BDNF gene, TrkB receptor
Obesity & Lifestyle
This constitute environmental factors that influence the risk of obesity
Low levels of physical activity & recreation predictive of weight gain in adults & children
Over-eating relative to energy expenditure
Socio-economic factors & Ethnicity
Socioeconomic class & prevalence of obesity negatively correlatedin most developed countries
Black men less obese than white men
Black & Hispanic women more obese than white women
Psychologic factors
Poor mood, depression, low self esteem may exacerbate overeating
Binge eating/eating disorders
CLASSIFICATION OF BMI
<18.5 kg/m2 –underweight
18.5-24.9 kg/m2 – normal
25-29.9 kg/m2– overweight
30.0 to 34.9 kg/m2 –Class 1 Obesity
35.0 to 39.9 kg/m2 – Class 2 obesity
≥ 40 kg/m2 – Class 3 obesity- Morbid obesity
Measures of body fat
WC in USA: >102 cm in men & > 88 cm in women
WC in Europeans: 94 cm in men & 80 cm in women
Skinfold thickness: less accurate & less convenient than WC & estimates subcutaneous fat instead of intra-abdominal fat
CT & MRI more accurate than waist circumference for assessing distribution of body fat but too expensive
Metabolic syndrome: check it out
How to measure waist and hip circumference
Waist circumference: midway way between lowermost rib margin & iliac crest
Hip circumference: largest horizontal circumference at widest diameter of the buttocks
Management of Obesity
Caloric restriction – wt loss of ~0.5 kg/wk can be achieved by daily intake by 500-1000 kcal below weight maintenance requirements
Exercise added to caloric restriction appears to be component of treatment most likely to promote long-term weight maintenance
Behavioural therapy: help develop adaptive thinking, eating, & exercise habits that decrease weight & avoid regain
Discuss Physical Activity
Although energy restriction by dieting is largely responsible for initial weight loss, regular physical activity helps to maintain weight loss & prevent weight regain
Regular exercise & aerobic fitness also: Individuals should engage in 30–45 min of moderate-intensity aerobic physical activity 3–5 days per week initially, gradually increasing the duration & frequency
improve insulin sensitivity & glycemic control
may decrease risk of developing type 2 DM
Pharmacologic therapy
Advocated for patients who have failed to achieve weight loss goals through a basic weight management program
May be used for patients with
BMI 30 kg/m2
BMI of 27 to 29 kg/m2 with obesity related comorbidity
Pharmacologic therapy
Appetite suppressants - Work primarly by ↑ availability of anorexigenic neurotransmitters in CNS
Noradrenergic agents: phentermine, diethylpropion, phendimetrazine, benzphetamine
Mixed Noradrenergic/Serotonergic agent: Sibutramine - inhibits reuptake of serotonin & norepinephrine
Side effects: Increased BP, pulse, dry mouth, headache, insomnia & constipation
Medications that alter Metabolism
Orlistat-Intestinal lipase inhibitor
Prevents GIT absorption of ~30% of dietary fat
Side effects- GIT upset, oily spotting, diaorrhea, faecal incontinence, potential malabsorbption
Anti depressants
Fluoxetine & sertraline: selective serotonin reuptake inhibitors (SSRI) approved for treatment of depression, may facilitate weight loss in the short term
May be preferred over other anti depressants for the obese
No of medications/experimental agents with differing mechanisms of action in trials to evaluate safety & efficacy in obese patients
Bariatric Surgery
Surgical therapy is currently the most effective treatment of obesity with respect to degree & duration of weight reduction achieved
Obese patients are candidates for surgery if medical therapy has failed & BMI > 40 kg/m2 or BMI > 35 kg/m2 with co-morbidity
Gastric bypass (GB) is by far the Most common available procedures
Others include:
Laparoscopic adjustable gastric banding (LAGB)
biliopancreatic diversion (BPD) without or with duodenal switch
vertical banded gastroplasty (VBG
