Epidemiology of obesity

Definition of Obesity

• Obesity can be defined as an excessive amount of body fat, which increases the risk of medical illness and premature death

• Recently, the World Health Organization proposed guidelines for classifying weight status by body mass index (BMI)

• BMI represents the relationship between weight and height and is calculated as weight (in kg) divided by height (in m2)

• or as weight (in pounds) times 704 divided by height (in inches2)

Patterning of Body Fat andDisease Risk

• Android (apple): Some people deposit more fat in their abdomen (abdominal obesity)

• Abdominal obesity is defined as a waist-to-hip ratio of greater than 0.9 in women and 1.0 in men.

• Gynoid (pear): others accumulate fat predominantly in the hips and thighs (lower body obesity).

• Lower body obesity is defined as a waist-to-hip ratio of less than 0.75 in women and 0.85 in men.

• People who have abdominal obesity are much more likely to develop diabetes mellitus, high blood pressure and heart disease than are persons with lower body obesity

Development of Adipose tissue

• As expected, studies have shown that nutritional and exercise interventions in the growing years, results in a LOWER FAT CELL NUMBER, and a subsequent decrease in relative RISK of obesity!!!

Obese individuals have a greatly increased risk of developing:

• diabetes mellitus, • high blood pressure, • Heart attacks and strokes. • arthritis, • congestive heart failure, • Breast cancer, uterine cancer, colon cancer, • sleep apnea, • gallstones• depression.

• The moderately obese (BMI . 32.5 kg/m2), middle aged men and women have double the risk of hypertension, triple the risk of type 2 diabetes, and a 1-year reduction in life expectancy compared with their nonobese peers

Willett WC, et al. N Engl J Med. 1999;341:427–434.

Relation Between BMI and Comorbidities

4

6

5

3

2

1

0

Body Mass Index

Relative Risk

Women Men

Body Mass Index

6

5

3

2

1

0

4

Type 2 diabetesCholelithiasisHypertension

Coronary heart disease

<21 22 23 24 25 26 27 28 29 30 <21 22 23 24 25 26 27 28 29 30

(kg/m2) (kg/m2)

Magnitude of the Problem

• According to a recent summary of statistics from the WHO 1.1 billion people worldwide are overweight

• This is the first time in recorded history that the number of people who are overweight equals the number of people who are underfed and underweight

1991 1995

2002

Obesity Trends* Among U.S. AdultsBRFSS, 1991-2002

No Data <10% 10%–14% 15%–19% 20%–24% ≥25%

*(BMI ≥30, or ~ 30 lbs overweight for 5’ 4” woman)

Middle East and North Africa(MENA) Countries

• Emerging data from developing countries indicate that the prevalence of obesity among children and adolescents is escalating more rapidly today than in industrialized countries

• by 2020, approximately three-quarters of all death in the developing countries will be related to non-communicable disease

• Obesity and/or overweight are major risk factors for chronic diseases

In the Kingdom of Saudi Arabia,

• The highest frequency was in the Eastern Province (Riyadh 18%), the lowest in the Southern Province (Sabea 11.1%).

• Overweight increased with age (the highest in boys 15–16 years old and in girls 17–18 years old).

• Family history, lack of physical activity and changing in eating habits were associated with adolescent obesity which becomes an important public health problem among male adolescents in Riyadh.

Energy Intake

EnergyExpenditure

High fat ,high-calorie diet Genetic

Predisposition

Sedentary lifestyle

Etiology of Obesity

• Weight gain can only occur when the input energy exceeds the output energy.

• input energy is the amount of food we eat. • Energy expenditure consists of our resting

metabolic rate (the amount of calories we use each day for vital functions such as breathing, circulation and maintaining body temperature) and the amount of physical activity we do.

imbalance between energy intake and energy expenditure is influenced by

A) Genetic factors: • Twin studies show that individuals with identical

genes are almost exclusively either both overweight or of normal weight.

• Children with one or both parents who are obese have a 2 times risk of being an obese adult.

Our genes affect our appetites, food preferences, resting metabolic rates, and our tendency to engage in physical activity.

• Genetics also strongly influence the pattern

of obesity (abdominal obesity vs. lower body obesity) and the age at which obesity develops.

• Study in Cambridge University has isolated at least two genes that when manipulated, control weight gain / loss (Leptin)

Leptin ?

• Leptin: A hormone like protein produced in the fat cells of the body.– When leptin levels are high in the blood stream…

appetite is suppressed. (Neg. Feedback loop)– It is believed that some people have genetic

abnormality…produce less leptin.– Possibly reversed through gene therapy?

Ethnicity and Obesity

Psychosocial factors associated with the incidence of obesity in ethnic minorities include

• inadequate social support• cultural barriers to communication• racism and discrimination• stress and lack of knowledge• language difficulties to understand the health

promotion message.

B) Socio-economic Environmental Factors

Obesity is strongly influenced by environmental factors, such as , income, housing condition, and work situation.

Income

• Obesity is strongly linked to poverty. • Poorer diets among poorer groups can be

explained by the lack of opportunities, stress, and level of knowledge.

• Poverty and overcrowding can inhibit parental supervision of children and negatively affect their health in general and increase obesity.

Genetics• Low Metabolism

•Poor Appetite Control• Low Fat Free Mass

• Low Levels of Lipid Oxidation

Rate

Environment• Sedentary Lifestyle

• Access to Food

Etiology of Childhood Obesity

C) behavioral factors:

• are also important since voluntary changes in Dietary intake and exercise can result in significant alterations in body weight.

• The average person with a stable weight consumes about 2,000-2,500 calories each day

Dietary Intake

• in order to gain a pound of fat a person must accumulate 3,500 excess calories. Only 7 excess calories per day will add up to a one pound weight gain over a period of one year.

Increased caloric intake from 1970 to 1990 due to:

– Increased portion sizes (“super-size”)– Increased frequency of eating outside the home– Increased fast food consumption– Fat-free foods perceived as low calorie or

calorie free

Increased Portion Sizes

Increased frequency of eating outside the home

• Average McDonald’s sandwich contains about 40% of an individuals daily intake requirement. (that’s excluding the fries)

Energy and Nutrient Intake in Obese vs. Non-Obese Children

• The literature on energy intake (EI) in obese vs. non-obese children includes examples of negative associations, positive associations and non-associations, using cross-sectional and prospective designs.

negative associations

• Negative associations between EI and obesity have been found in a number of cross-sectional studies (Bratteby et al. 1998; Hassapidou et al. 2006; Sjöberg et al. 2003). In one of these studies, the association was negative in girls but not in boys, a difference attributed to sex influences on underreporting (Sjöberg et al. 2003).

• Although it is often assumed that such associations are artifacts of obesity-related underreporting, low physical activity seems likely to be part of the explanation

positive associations

• In contrast, several studies have provided evidence of positive associations between energy intake and obesity.

• In one study using diet history, children and adolescents with obesity had significantly higher EI than non-obese children, independent of physical activity patterns

• Finally, it must be noted that a number of cross-sectional and prospective studies have not detected any relation between EI and overweight/obesity (Aeberli et al. 2007; Andersen et al. 2005; Maffeis et al. 1998; Maffeis et al. 2000; Rolland-Cachera and Bellisle 1986).

• One of these studies however found a positive relation only when studying EI at dinner meals (Maffeis et al. 2000).

Fat and Fat Type

• The literature on dietary fat intake in obese vs. non-obese children is also mixed and may further depend on whether fat is measured in the absolute or as a percent of total energy (E%).

• For instance, in a cross-sectional study including adolescents, there was a positive association for E% of fat but not for intake of fat in grams per day (Ortega et al. 1995);

• however, the opposite, significant positive associations for fat in grams but not in E% has also been reported (Gillis et al. 2002)

• However a number of studies have reported no associations between dietary fat and childhood obesity (Aeberli et al. 2007; Andersen et al. 2005; Atkin and Davies 2000; Berkey et al. 2000; Davies 1997; Maffeis et al. 1998; Rolland-Cachera and Bellisle 1986; Scaglioni et al. 2000).

Physical Activity

• Increased use of labor saving devices.

• Decrease in the energy cost of everyday activities.

Labor Saving Devices

• Tele-commuting Personal computers• Cellular phones Internet / E-mail• Food deliveries E-Commerce• Escalators/elevators Pay per view movies• Computer games Moving sidewalks

• Drive-in windows Garage door openers• Intercoms Remote controls

Physical Activity

• Activity blunts the weight gain seen with aging.

• Studies in active adults–No statistical relationship between caloric

consumption and body fat percentage–Linear relationship between activity level and

body fat%.• Reduced physical activity is the MAIN

cause of adult obesity!

Health Benefits of Weight Loss

• Weight loss of 5% to 10% in obese individuals with type 2 diabetes, HTN or dyslipidemia results in:– Improved glycemic control– Reduced blood pressure– Improved lipid profile

• Goldstein DJ. Int J Obesity 1992;15:397-415. Wing RR, et al. Arch Int Med 1987;147:1749-1753