Obesity is caused by excessive accumulation of fat. A positive energy balance results first in swelling (a tenfold increase in diameter) and then in the creation of new cells to store the energy. Therefore, increased adipose tissue mass is a result of hypertrophy (increased size) and/or hyperplasia (increased number) of cells. In the obese, adipose tissue accounts for more than 25% and 30% of the body weight in men and women respectively, a percentage that can reach or exceed 50% of the weight.
Obesity is a widespread problem with increasing dimensions in all societies. Its incidence increases with age and varies from country to country and from region to region within the same country. It is estimated that around half of European adults aged 35-65 are overweight or obese. Thus, in Europe, obesity occurs at a rate of 10-20% of men and 15-25% of women, with a tendency to further increase. In the US the incidence of obesity has increased significantly in the last 10 years, so recent studies show that ~45% of the population are overweight or obese.
On the contrary, there are indirect ways of assessing obesity with anthropometric indicators:
Reference body weight (BW) tables for height, such as Metropolitan Life Insurance Co. (1959), revised in 1985 give some criterion for BS. People with a BMI >20% of the "ideal" (100%) are considered obese. These charts are flawed and no longer used because weight is estimated based on body type (thin, regular, stocky) relative to height and frame is generally estimated rather than bone measurements.
The body mass index (body mass index, BMI), which expresses the weight/height ratio2 (in kg/m2), has a good correlation with body fat percentage. In 1995 the World Health Organization (WHO) proposed BMI limits. Lately, obesity has been found to be a problem in childhood and adolescence as well. Relatively recent (1995) data from the USA indicate that as many as 20% of children are overweight or obese and that the majority remain in this condition well into adulthood.
Classification of body weight according to BMI
|BMI (kg/m2)||Classification by WHO||Description|
|18.5 – 24.9||Normal weight||healthy, normal|
|25 – 29.9||overweight||overweight|
|30 – 34.9||Obesity grade 1||obese|
|35 – 39.9||Obesity grade 2||obese|
|≥40||Obesity grade 3||morbidly obese|
Obesity has been known since ancient times. "Fatness shortens life", a popular maxim - a faithful translation - of the Hippocratic saying "those who are severely obese die quickly", has been confirmed in the last 35 years by most epidemiological and other scientific works. It is argued that obesity is not a condition that leads to morbidity, but is a disease, perhaps the main one associated with a "Western-style" diet and lifestyle.
The association between mortality and BMI shows a parabolic curve and increases significantly with BMI >30 kg/m2. It appears that people with BMI <19 kg/m2 have an increased risk of mortality, but this is not the case if people who smoke or have other underlying disease are excluded from the calculations.
|Cardiovascular||hypertension, coronary artery disease, cerebrovascular disease, deep vein thrombosis, varicose veins|
|Respiratory||hypo-ventilation syndrome, sleep apnea syndrome|
|Metabolic disorders||dyslipidemia, insulin resistance, DM type 2|
|Digestive||cholelithiasis, fatty liver, cirrhosis|
|Endocrine||increased cortisol response to stress and increased turnover, decreased GH|
|To women||conversion of androgens to estrogens, hyperandrogenemia, menstrual disorders, SHBG reduction|
|To men||conversion of androgens to estrogens, gynecomastia, reduction of free testosterone|
|Skin||stretch marks, mycosis, cellulitis, lymphedema|
Obesity and mortality
|CORONARY ARTERY DISEASE||1.85||2.07|
GRADUATE COURSES IN ENDOCRINOLOGY AND DIABETES- DEPARTMENT OF ENDOCRINOLOGY DIABETES AND METABOLISM OF EVANGELISMOS GENERAL HOSPITAL OF ATHENS- 2004