Community MedicineLecture - 10 -

الرحيم الرحمن الله بسم

Learning objectivesAt the end of this lecture student would be able to:

1-Explain difference between over weight & obesity.

2-Define the ideal body weight. 3-Classify body fats.

4 -Determine epidemiological facts about obesity.

5-Enumerate causes of obesity. 6-Illustrate methods of obesity

classification . 7-Demonstrate methods of obesity assessment .

8-Mention medical complications of obesity . 9-Discuss possible measures for weight reduction .

Obesity

Obesity is a medical term for over fatness frequently resulting in a significant ill health. It refers to excess body fat. It is an accumulation of adipose tissues.

The body weight increase 20% or more above the IBW .

It is considered as a chronic disease associated with illness & death from complications.

Over weight: is the excess wt/ht by standard tables 10% of IBW . Ideal body weight: is the body wt. for a given ht. that statistically associated with the greatest longevity.

Two kinds of human body fats :1-Essential fat :vital to health (it cushion &protect body organs),3-8% of

B.W.2-Storage fat: layers& cushion of fat providing stored energy.

• Gender specific fat: In women breasts& pelvic region. Normal proportion of body weight(as fat) is 15-20% for men& 20-25% for women.

During 20s of age , man has 15% body fat; 3% essential & 12% storage fat.Woman of the same age has 25% body fat; 13% essential & 12% storage fat.

Epidemiology: Prevalence of obesity all over the world is increasing,

especially in USA. But the mortality rate has decreased especially in women over 45 years (group of highest prevalence of obesity).

Prevalence of obesity in western world begin in infancy, 1/3rd or more of their infants are obese, school children obesity vary between 6-15% .

The more the obesity in childhood the more the obesity in adulthood.

Young women are more likely to be obese than young men.

Epidemiological studies shows a strong association between socioeconomic status & the prevalence of obesity (inversely related) .

30% of low socioeconomic individuals are

obese.

Causes of obesity :1-Metabolic causes: 2-Sedentary life style.3-Emotional:4-Familial cause (genetically predisposed) :Two obese parents have a 73% chance of having obese offspring.

5- Brown fat: some people seems to eat more than others without gaining weight due to brown fat hypothesis :

Cytochrome –pigmented brown adipose tissues which occur only in certain areas of the body (around neck & chest)& not develop after birth; these tissues are rich in mitochondria & produce heat. It serves as caloric buffer that disposes energy excess when food intake is high & conserves energy when food intake is low.

6-Lipoprotein lipase: it can potentiate hunger by altering the availability of circulating metabolites.

7-Role of leptin: mutation in a gene Ob causes a severe hereditary obesity .

Classification of obesity:There are different classifications .1-Hypertrophic obesity: result from an increase lipid content

of adipocytes . It is common in adults (mild to moderate obesity).

2- Hyperplasic- hypertrophic obesity: increase in the fat cells number & lipid content of fat cells .

Over feeding during infancy & adolescent lead to permanent abnormality, therefore preventive measures should taken during these age periods .

Other classification; regional fat distribution;*Android =Apple shaped (upper body) obesity: excessive

fat located in the central abdominal area which is statistically associated with increased risk of Diabetes , hypertension & CVD (common in males).*Gyroid = pear shaped (lower body) obesity: the fat distributed in the lower extremities around the hips or femoral

region, relatively benign (common in females).

Assessment measures of obesity:A-Body weight:B-Height:C-BMI:Is the ratio of weight in kilogram (with minimal clothing) to height (without shoes) in meter

square.For both male &female, the degree of obesity is classified

as:-BMI 20-24.9 (normal or desirable weight range).-BMI 25-29.9 (over weight) low relative risk.-BMI 30-40 (moderate obesity) moderate risk = grade I&II -BMI > 40 (morbid obesity) high risk =grade III

Relationship between body mass index and mortality rate . The lowest mortality rates are associated with BMIs between 19 and 27 kg/m2

D-Waist to hip ratio: Waist to hip circumference can identify the two types of

obesity.• A ratio of 0.7 considered as normal.

• A ratio < 0.7 indicates lower body obesity.

• A ratio > 0.7 indicates upper body obesity.

Fat below the waist is more difficult to lose than above the waist.

E-Skin fold thickness: About half of body fat is deposited under the skin &the

rest is around the organs &between muscles fibers.

The fat is not distributed equally under the skin throughout the body. Therefore, the measurement should be made at some selected sites.

Compared with reference standards tables to assess the fat thickness.

*18mm for men ,>20 means excess fat.*23mm for women, >25 means excess fat.

Medical complications:Obesity is associated with a number of chronic diseases Including:1-Adult onset diabetes, 2.9 times higher prevalence. F.B.G.

incr. about 2mg/dL for each 10% above I.B.W. (the body resist his own insulin).

2-Hypercholesterolemia, high plasma T.G., 2mg/dL for each kg excess of B.W., with incr. VLDL.(relative risk increased 4 folds with obesity)

3-Hypertension & heart disease, there is linear association (relative risk increased 5 folds with obesity).

4-Cancer; higher mortality from cancer of colon& prostate in males, & breast in females.

5-Gall stones (related to increased cholesterol synthesis)6-Arthritis, & gout.7-Undesirable social,& psychological consequences .8-Heavy menstrual blood flow, irregular cycle,& infertility.9-Decreased life expectancy

On the other hand risk of osteoporosis is lower with obesity.

Weight reduction strategies:Body weight represents the balance between energy intake & energy expenditure. To reduce body weight requires negative energy balance. 1-Diet; to lose 500gm/week , patient should reduce caloric intake by 500Kcal/day i.e. 3500Kcal/week (max. loss 2kg/month).

2-Exercise; increase physical activity which result in expenditure of 500Kcal ( running for 45min. )

3-Behavioral modification: eating when hungry,& stopping with first sign of satiety, small, regular & frequent meals.4-Surgical treatment (for morbid obesity), creating smaller bowel( produce malabsorption of calories), or creating small stomach to reduce the reservoir for food .