Obesity is a condition in which excessive body fat has
accumulated to the level that it may have an adverse effect on health, leading
to reduced life expectancy and/or raised health problems.
Measurements of
obesity
Obesity represents a condition associated with excess
storage of body fat. Although similar, the term overweight is puristically
thought as an excessive amount ofbody weightfor height. Normal, healthy men
have a body fat proportion of 15-20% , while normal, healthy women have a
percentage of about 25-30%.[4] Nevertheless, because differences in weight
involving individuals are simply partly caused by variations in body fat, body
mass is really a limited, although easily obtained, index of obesity.
The ways to establish obesity is to work with this technique
of measurement are :
1. The body mass index (BMI) , also known
as the Quetelet index, is needed far more usually than body fat percentage to
determine obesity. Generally, Body mass index correlates intimately with the
level of body fat in most settings; however, that correlation is weaker at low
BMIs.
The individual’s BMI is calculated as bodyweight (kg)/height(m2)
,
with weight in kgs and height in meters (in any other case, the equation is
weight in pounds ´ 0.703/height in inches2). Online BMI calculators can be
found.
2. Deurenberg formula, as follows:
body fat percentage = 1.2(BMI) + 0.23(age) - 10.8(sex) - 5.4
with age in years and gender being designated as 1 for males
and 0 for women. This equation has a standard error of 4% and accounts for more
or less 80% of the variation in body fat.
Although the BMI typically correlates closely along with
percentage body fat in a curvilinear fashion, some important caveats apply to
its interpreting. In mesomorphic (muscle) people, BMIs have a tendency to show
over weight or slight obesity could be spurious, whereas in some individuals
along with sarcopenia (such as, aged men and women and persons of Asian origin,
especially from South Asia), a typically normal BMI may cover up actual
excessive adiposeness seen as a an elevated proportion of fat mass and
decreased muscle mass.
In view of those disadvantages, many authorities recommend a
definition of obesity depending on percentage of body fat. For men, a
percentage of body fat in excess of 25% identifies obesity, with 21-25%
becoming borderline. For women, in excess of 33% defines obesity, along with
31-33% staying borderline.
3. Some standard skin thicknesses
Subscapular, triceps, biceps, suprailiac) and also numerous
anthropometrical measurements, of which midsection and hip circumferences are
the most significant. Skinfold measurements are the least correct signifies by
which to assess obesity.
4. Dual-energy radiographic absorptiometry
(DXA) scanning is used principally by researchers to accurately measure
entire body composition, particularly body fat mass as well as fat-free mass.
It offers the additional benefit of measure regional body fat distribution.
However, DXA scans can't be utilized to separate between subcutaneous and
visceral abdominal fat deposits.
5. Abdominal computed tomography (CT) scanning
(at L4-L5) as well as magnetic resonance imaging (MRI) methods. An easier
technique, using bioelectrical resistance, was lately introduced. However,these
methodsare 1 clinical research.
Classification of
obesity
Although several classifications and definitions for degrees
of obesity are accepted, the most widely accepted classifications are those
from the World Health Organization (WHO), based on BMI. The WHO designations
include the following:
Grade 1 overweight (commonly and simply called overweight) -
BMI of 25-29.9 kg/m2
Grade 2 overweight (commonly called obesity) - BMI of
30-39.9 kg/m2
Grade 3 overweight (commonly called severe or morbid
obesity) - BMI greater than or equal to 40 kg/m2
Etiology
The etiology of obesity is far more complex than simply an
imbalance between energy intake and energy output. Although this view allows
easy conceptualization of the various mechanisms involved in the development of
obesity, obesity is far more than simply the result of eating too much and/or
exercising too little (see the energy-balance equation, below). Possible
factors in the development of obesity include the following: Metabolic factors,
Genetic factors, level of activity, Endocrine factors, Race, sex, and age
factors, Ethnic and cultural factors, Socioeconomic status, Dietary habits,
Smoking cessation, Pregnancy and menopause, Psychological factors, History of
gestational diabetes, Lactation history in mothers.
Prognosis
For a person with a BMI of 25-28.9 kg/m2, the relative risk
for coronary heart disease is 1.72. The risk progressively increases with an
increasing BMI; with BMIs greater than 33 kg/m2, the relative risk is 3.44.
Similar trends have been demonstrated in the relationship between obesity and stroke
or chronic heart failure.
Overall, obesity is estimated to increase the cardiovascular
mortality rate 4-fold and the cancer-related mortality rate 2-fold.[54] As a
group, people who are severely obese have a 6- to 12-fold increase in the
all-cause mortality rate. Although the exact magnitude of the attributable
excess in mortality associated with obesity (about 112,000-365,000 excess
deaths annually) has been disputed, obesity is indisputably the greatest
preventable health-related cause of mortality after cigarette smoking.
For persons with severe obesity (BMI ≥40), life expectancy
is reduced by as much as 20 years in men and by about 5 years in women. The
greater reduction in life expectancy for men is consistent with the higher
prevalence of android (ie, predominantly abdominal) obesity and the
biologically higher percent body fat in women. The risk of premature mortality
is even greater in obese persons who smoke.
Some evidence suggests that, if unchecked, trends in obesity
in the United States may be associated with overall reduced longevity of the
population in the near future. Data also show that obesity is associated with
an increased risk and duration of lifetime disability. Furthermore, obesity in
middle age is associated with poor indices of quality of life in old age.
Individuals who have abdominal obesity (elevated waist
circumference) are at risk for obesity-related health complications. Most
individuals with a BMI of over 25 and essentially all persons with a BMI of
more than 30 have abdominal obesity.
Factors that modulate the morbidity and mortality associated
with obesity include the following:
Age of onset and
duration of obesity, Severity of obesity, Amount of central adiposity,
Comorbidities, Gender, level of cardiorespiratory fitness, Race.
Weight-loss programs
Most individuals are able to attain weight loss in the short
term, but weight regain is unfortunately a common pattern. On average,
participants in nonsurgical weight-management programs lose approximately 10%
of their initial body weight over 12-24 weeks, but the majority regain two
thirds of the weight lost within a year.
Old data indicated that 90-95% of the weight lost is
regained in 5 years. Recent data show that more intensive and structured
nonsurgical weight management may help a significant number of patients to
maintain most of the weight lost for up to 4 years.
In the Look AHEAD study, 887 of 2570 participants (34.5%) in
the intensive lifestyle group lost at least 10% of their weight at year 1. Of
these, 374 (42.2%) maintained this loss at year 4 and another 17% maintained
7-10% weight loss at 4 years. More than 45% of all intensive lifestyle
participants had achieved and maintained a clinically significant weight loss
(≥ 5%) at 4 years.
