By Gianluca Tognon
Obesity is defined as an excessive accumulation of adipose tissue compared to lean tissue. Technically, a person is considered obese when his body mass index (BMI) is greater than 30. To understand the importance of this problem from a health point of view, one just need to think that some years ago, the WHO defined obesity as one of the major public health problems in the world together with climate change. Only in the United States, one-fifth of adults are obese, while more than a billion people worldwide are overweight (and 300 million of these are obese).
Obesity leads to a higher risk to develop major chronic diseases such as cardiovascular disease, stroke, diabetes, some cancers (endometrial, colorectal, kidney, pancreas, breast, esophagus), gallbladder disease, osteoarthritis. Other problems associated with this disease are represented by high blood pressure, high cholesterol, respiratory problems, increased surgical risk, pregnancy complications, hirsutism, menstrual irregularities.
In many European countries the prevalence of obesity has tripled since the 80s. The social cost of this condition is now equal to 6% of healthcare costs in Europe. Obesity is also the most common childhood disorder in Europe (20% of overweight children of which one third obese).
Abdominal obesity and cardiovascular risk
Many studies show that abdominal obesity is associated with a number of negative consequences, among which an increased cardiovascular risk, a higher risk of developing diabetes, which in turn increases the cardiovascular risk, an increased cancer risk. The danger for the cardiovascular system comes from the excess fat inside the abdomen (intra-abdominal adiposity) which becomes dangerous when waist circumference exceeds 88 cm in women or 102 cm in men. The abdominal adipose tissue has an active metabolic role. For example, it produced:
- substances that can promote the formation of plaques;
- substances that favour insulin resistance and promote the development of diabetes;
- free fatty acids that act on the liver, increase insulin resistance and alter the levels of fat and sugar in the blood;
- substances that can trigger inflammatory processes that cause the formation and progression of plaque in the arteries.
Furthermore, abdominal obesity predisposes to the development of:
- hypertension;
- changes in blood lipids (triglycerides, LDL, HDL).
Obesity can be the result of another disease or condition, for example:
- hypothyroidism;
- Down syndrome;
- polycystic ovary syndrome;
- disorders of the hypothalamus;
- antipsychotic drugs/antiepileptic drug use;
- high doses of corticosteroids.
Non-dietary factors
Age – The weight generally tends to increase (often slowly) between the age of 20 and 50. In general, lean body mass decreases in favour of fat mass, resulting in a decreased basal metabolic rate. Other factors associated with weight gain in adult life are reduced physical activity, marriage, a higher food intake and stress at work.
Socioeconomic position – The cost of food is often proportional to its healthiness. Many foods rich in energy and, particularly, high in energy density (e.g. fatty meat, cold cuts, etc..) often have a lower price than other food which contain less calories (such as fruit, vegetables or fish). This can partly explain why people who have limited economic opportunities are generally more prone to gain in weight.
Sedentary lifestyle – The increased time spent doing sedentary activities both at work and at home (particularly after the advent of television, computers and home appliances) is one of the underlying causes of the obesity epidemic. A more hectic life (or just the laziness favoured by technology) has also led to a reduction of the time that is devoted to sport.
Other factors – Low birth weight, lack of breastfeeding, weight and parental habits can also affect the risk of being overweight or obese.
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