Obesity phenomenon: data at hand
According to the results of the Istat Multipurpose Survey on the issue, it emerged that in Italy, in 2013, 35.6% of the adult population was overweight, while one person in ten was obese. The percentage of excess weight population increases with age and, in particular, the overweight goes from 15.8% from 18-24 years to 45.8% between 65-74 years, while obesity from 2 , 8% to 15.9% for the same bands. In the more advanced ages the value decreases slightly compared to the previous age group. Furthermore, the excess weight condition is more prevalent among men than women (overweight: 44.2% vs. 27.6%, obesity: 11.3% vs. 9.5%). Until 1980, only one person in fifty was obese, but then there was a doubling and even a tripling of rates in nineteen of thirty-four European countries, so most of the population is now overweight or obese. In 2008 across Europe over 50% of men and women were overweight and about 23% of women and 20% of men had frank obesity. In 2010, thirty-six states had an obesity rate of 25% or more, and twelve of them reached at least 30%. According to the latest estimates, always in EU countries, overweight would affect 60% of adults and obesity 10-30%. The projections, however, indicate that by 2020, in some countries, 7 out of 10 people will be overweight or obese. The WHO predicted that overweight adults would rise to 2.3 billion and over 700 million with obesity by 2015. Moreover, with the aging of the world population, it is now estimated that for most of the countries of the world about 20% of people after age sixty five are affected by obesity. Under defined aspects, the current global epidemic of obesity must be regarded as a non-transferable process in the context of globalization.
In fact, with regard to Public Health, this process has an important impact on both economic and social determinants. In this regard, there is growing evidence that global lifestyle trends, eating behavior and cultural adaptation all contribute to the rapid rise of the disease. There is, unfortunately, to be considered that in many parts of the world there is still the awareness that obesity is an epidemic disease, as a response in the last forty years to the drastic and progressive reduction of physical activity and to the major changes in the food supply of countries. The WHO has estimated that globally 3.4 million adults die each year from causes related to overweight and obesity. It is estimated that 23% of cardiovascular diseases, 44% of diabetes cases, and almost 25% of some cancers are attributable to excess weight. But the list is not over. Increasing evidence indicates that obesity can lead to other diseases not least, due to the economic impact they have on public health: osteoarthritis, pulmonary diseases, venous thrombosis and infertility. Only for cardiovascular risk, it is considered that a weight loss of 6-7 kg is able to determine a 50% reduction in the risk of re-infarct. A body weight loss of 10% reduces the systolic and diastolic blood pressure by almost 10%. Hypertension, in fact, is known to be a risk factor associated with cardiopathies; a decrease of 5 kg also reduces the risk of developing diabetes by 50%. Finally, reducing the BMI by 2 units reduces the risk of developing osteoarthritis by 50%.
The diagnostic factor
Making sure of the presence of indices or markers connected with the possibility of developing obesity could be easier than you think. Incredibly, VES and C-reactive protein (CRP) were the unique inflammatory indices of laboratory medicine. But other plasma proteins can be good diagnostic markers of inflammation. VES and PCR are defined as “acute phase proteins” and indicate only the presence of an inflammation; but they do not specify where it is or its course. Obesity alters systemic metabolic homeostasis and induces an increase in visceral adipose tissue, which in turn produces an inflammatory process with an increase in numerous pro-inflammatory cytokines. Under normal conditions, white adipocytes accumulate lipids while white tissue macrophages release arginase and anti-inflammatory cytokines (IL-10 and IL1RA). In conditions of obesity, the visceral white adipose tissue becomes inflamed by a combined action between adipocytes and macrophages: the first grow in number and size, the latter infiltrate the tissue, aggregating around adipocytes in decay. Of all the adipokines secreted by adipose tissue, over twenty present circulating concentrations increased in obese subjects: some of these such as CRP, haptoglobin and amyloid-A are proteins of the acute phase, mainly produced in response to the induced inflammatory stimulus from visceral obesity. Many of the remaining molecules are inflammatory cytokines produced by macrophages, except FABP-4 and leptin, which are produced by fat tissue instead.
An analysis of the literature (2010) referring to the use of quantitative determination with immunometric methods of different human adipokines circulating in obesity and in the metabolic syndrome, shows that on about 300 total works the ELISA method is used directly or for comparison in all do you study. Among the detected adipokines, leptin was assayed alone or in association in 168 studies (55.8%), adiponectin was investigated in 77 studies (25.6%) and resistin in 25 (8.3%); 37 other adipokines were examined, with a number of studies ranging from 1 to 8 for each of them. Other studies have focused on haptoglobin, which is partly produced by adipose tissue, whose plasma concentrations correlate with those of insulin, independently of other metabolic and cardiovascular risk factors. Interleukin 6 (IL-6) is a pro-inflammatory cytokine also produced in part in adipose tissue. There is a close relationship between degree of obesity and IL-6 concentrations, confirming that obesity is characterized by a generalized low-grade inflammation. IL-6 can be easily measured in blood plasma; therefore it could be among the easy-to-detect markers of pre-obesity hidden inflammation. The same applies to the tumor necrosis factor (TNF-alpha), another high cytokine in systemic or organ flogosis, which is easily measurable in both plasma and urine.
Abdominal obesity is associated with both an altered endothelial function and a thickening of the carotid intima-media complex, which correlates with what occurs in the coronary arteries. Endothelial dysfunction is characterized by a reduction in the production of nitric oxide (* NO) with vasoconstriction, increased vascular resistance and an increase in blood pressure. * NO deficiency is related to oxidative stress, as demonstrated by the increased urinary elimination of 8-epi-prostaglandin F2 alpha (8-epi-PGF2a). This can become a marker of oxidative stress that signals inflammatory and oxidizing conditions, in case of both obesity and diabetes mellitus and metabolic syndrome. Another catabolite index of dosable oxidative damage in the urine is 8-hydroxy-guanosine (8-OH-dG), which is a specific marker of nucleic acid damage. Its presence in excess in the urine, in apparent absence of obesity or diabetes, could represent an early marker of cell injury in progress.
- a cura del Dr. Gianfrancesco Cormaci, PhD, specialista in Biochimica Clinica.