Obesity is a growing epidemic worldwide that has nearly doubled since 1980. In 2008, more than 1.4 billion adults over 20 were overweight, almost 35% of the population and about 11% were obese.
More than 40 million children under 5 were overweight in 2011, about 10 million in the developed and 30 million in the developing countries, which demonstrates that this disease is becoming an increasing problem in the latter, that used to fight undernutrition instead. Already being considered the fifth leading risk factor for global deaths, obesity kills at least 2.8 million adults each year.
It is a major risk factor for the development of cardiovascular diseases, type 2 diabetes mellitus, musculoskeletal disorders and various kinds of cancer.1 The enormous social and economic costs of obesity and these associated comorbidities are already threatening to overwhelm health care systems worldwide.
The World Health Organization (WHO) defines obesity as an abnormal or excessive fat accumulation that may impair health, the result of an energy imbalance between calories consumed and expended. The criteria used by WHO to diagnose obesity is the body mass index (BMI): A person with a BMI greater or equal to 25 is considered overweight; greater or equal to 30 is considered as having obesity.
In turn, obesity is also divided into three categories: BMI between 30 and 35 represents 1st-degree obesity; BMI between 35 and 40 represents 2nd-degree obesity; BMI over 40 represents 3rd-degree obesity.1 BMI is a useful indicator of overall adiposity, but different fat compartments are associated with differential metabolic risk.
Thus, an evaluation of waist circumference results in a more accurate classification of obesity: visceral/central or subcutaneous obesity. A waist circumference over 88cm for women and over 102cm for men represents that a person has visceral/central obesity.3
However, besides the environmental cause described by WHO, genetic, neural and endocrine factors have been described as causes of obesity,4 as well as infectious agents.5 Evidence so far demonstrates that the bacteria that are commonly found in the human gastrointestinal tract, normally referred to as gut microbiota, affect nutrient absorption and energy regulation, while also being different in an obese person, when compared to a lean one.
This suggests that an important role is played by gut microbiota in the development of obesity.2 This information may represent a major advance in obesity therapy, since modifying the gut microbiota, through a diet rich in probiotics can become an important treatment option for obesity.2.
In fact, multiple studies have been researching the effect of the referred probiotics diet in the organism and its possible contribution to treating obesity as well as other comorbidities.6 Amongst the species already studied, the most commonly used are Lactobacillus spp., Bifidobacterium spp. and Enterococcus spp.6
Although there are several studies concerning the effect of different probiotics on weight change and obesity, we were unable to find a systematic review that summarized and discussed them in a global perspective. Thus, the elaboration of this article constitutes a relevant effort to better understand this matter.