Epidemiology of obesity
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
Patterning of Body Fat and
• Android (apple): Some
people deposit more fat in
their abdomen (abdominal
• 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
predominantly in the hips
and thighs (lower body
• 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
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:
high blood pressure,
Heart attacks and strokes.
congestive heart failure,
Breast cancer, uterine cancer, colon cancer,
• 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
Relation Between BMI and
Type 2 diabetes
Willett WC, et al. N Engl J Med. 1999;341:427–434.
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
Obesity Trends* Among U.S. Adults
(*BMI ≥30, or ~ 30 lbs overweight for 5’ 4” woman)
Middle East and North Africa
• Emerging data from developing countries
indicate that the prevalence of obesity
among children and adolescents is
escalating more rapidly today than in
• 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
• 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.
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
• Study in Cambridge University has isolated
at least two genes that when manipulated,
control weight gain / loss (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
– 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
B) Socio-economic Environmental Factors
Obesity is strongly influenced by
environmental factors, such as , income,
housing condition, and work situation.
• 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.
Etiology of Childhood Obesity
•Poor Appetite Control
•Low Fat Free Mass
•Low Levels of
•Access to Food
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
• 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
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
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 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
• 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
• 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).
• Increased use of labor saving devices.
• Decrease in the energy cost of
Labor Saving Devices
Tele-commuting Personal computers
Internet / E-mail
Escalators/elevators Pay per view movies
Computer games Moving sidewalks
• Drive-in windows Garage door openers
• Activity blunts the weight gain seen with
• Studies in active adults
– No statistical relationship between caloric
consumption and body fat percentage
– Linear relationship between activity level and
• 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