The Effects Of Physical Activity On Obesity Among The Population Of Different Ages: A Systematic Review

The aim of this research is a systematic review of the available literature with the effects of physical activity (aerobic training, strength endurance training, etc.) on the obesity of the population of different ages. For collection of previous research on the impact of physical activity on motor fitness, the following electronic databases were searched: PubMed, SCIndeks, PEDro, J-GATE, SCIndes, DOAJ and Google Scholar. The works in the period from 2000 to 2019 were searched. The following keywords were used in the database search: exercise, physical activity, children, adult, aerobic training, resistance training, walking. This systematic review was conducted in agreement with the PRISMA guidelines. The results of the analyzed works indicated that only 20 works met the set selection criteria. In the analyzed works were 845 respondents. In the most researches, the training program lasted 12 weeks, while the shortest program lasted only 5 weeks. Combining endurance training with aerobic training has been shown as the most effective method in the prevention and treatment of obesity.


Introduction
Diet and physical activity directly affect the health status of adults and children (Strong et al., 2005;Warburton, Nicol, & Bredin, 2006;Janssen & Leblanc, 2010;Petrović -Oggiano, Damjanov, Gurinović & Glibetič, 2010;Mitić, 2001;2011). The generally accepted scientific definition identify physical activity as "any bodily movement produced by skeletal muscles that results in energy expenditure" (Caspersen, Powell, & Christenson, 1985). Physical activity is one of the key determinants of energy consumption and for this reason is very important for maintaining energy balance and weight control (World Health Organization, 2000;2016).
To determine the prevalence of obesity and obesity in the population, the most commonly used estimate of nutritional levels based on body mass index (BMI -body mass index), which represents the ratio of body weight and square height. Previous research has shown that physical inactivity is negatively associ-ated with BMI, waist circumference, and body fat percentage in both sexes (Du et al., 2013;Kaleta, Makowiec-Dabrowska, & Jegier, 2007). Physical activity increases energy consumption and thus affects the overall daily balance of energy intake and consumption. Weight gain occurs when the energy balance is positive, i.e. when energy intake is greater than consumption. (Zdravković, Banićević, & Petrović, 2009).
In children and adolescents, the definition of obesity is more complex because the total body fat content depends on the chronological age, sex and stadium of pubertal development (Leskošek, 1971). In children, due to normal changes in BMI (body mass index), specific for age and sex, percentiles are used, which are determined by entering the calculated BMI in the growth chart of body mass index specific for the sex of the respondents. At the age of 20, the value of BMI above the 85th percentile represents overnutrition, i.e. risk of obesity, from the 95th percentile is defined as obesity. Less than 5% of childhood causes of EFFECTS OF PHYSICAL ACTIVITY ON THE OBESITY | M. STANKOVIC ET AL. obesity are secondary obesity, associated with genetic disorders, endocrine diseases, lesions of the central nervous system or iatrogenic causes (Leskošek, 1971). The most significant factors that contribute to the growing obesity epidemic are physical inactivity, sedentary lifestyle and changes in diet (Štimec, 2012). Based on the aforementioned factors that contribute to the growing obesity epidemic, it can be concluded that physical activity is one of the most important factors for the prevention and treatment of obesity (Lee, Djoussé, Sesso, Wang, & Buring, 2010;Saris, 1998).
The aim of this systematic review was to gather available information on the impact of different types of physical activity on obesity depending on age and to draw a conclusion from this which physical activity gives the best results in practice.

Inclusion criteria
For an experimental study to be included in the final analysis, it had to meet certain criteria: the participant in the research were individuals suffering from obesity; the experimental study included subjects of both sexes; respondents participate in exercise programs during which its effects were evaluated and measurements taken of the parameters of body composition; the research was published in English or Serbian. The exclusion criteria included: papers not published in English or Serbian, studies in which the effect of physical activity on body composition has not been analyzed.

Search strategy
To collect previous research on the impact of physical activity on motor fitness, the following electronic databases were searched: PubMed, SCIndeks, PEDro, J-GATE, SCIndes, DOAJ and Google Scholar. The works in the period from 2000 to 2019 were searched. The following keywords were used in the database search: exercise, physical activity, children, adult, aerobic training, resistance training, walking. The found research titles, abstracts and full texts were then read and analyzed. This systematic review was undertaken in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement (Moher et al., 2009).

Data extraction and selection
Experimental research which met the set criteria was then analyzed and presented based on the following parameters: references (the initials of the author and year of publication), the sample of participants (gender, BMI, age, overall number and subgroups of the participants), physical exercise program, the duration and frequency of exercise, research results.

Study quality and risk of bias
Risk of bias was evaluated according to the PRISMA recommendation and two independent reviewers assessed the risk of bias. When there was disagreement about the risk of bias a third reviewer checked the data and took the final decision on it.

Synthesis of results
By searching the electronic databases, 750 experimental studies were identified on the set topic. Primarily 195 studies were eliminated as duplicates, then 453 papers were rejected based on abstracts, while 82 studies were excluded because they were of the review type, or were not written in English. Applying the set criteria, the final analysis included 20 experimental studies.   nik et al., 2015). There were 845 participants overall, where 358 were children and 487 were adults. Lee et al., (2012) was only study with male participants, boys aged 12 to 18 years. In 11 of the 20 papers, subjects were of both sexes (Alberga et al., 2013;Dobrosielski et al., 2015;Farris et al., 2011;McGuigan et al., 2009;Mendelson et al., 2015;Prado et al., 2009;Rey et al., 2017;Saif & Alsenany, 2015;Van der Heijden et al., 2010;Wong et al., 2008;Yu et al., 2005).

Discusion
This analysis of previous experimental work provides an opportunity to see which types of physical activities are used to combat obesity. Certainly the most common type of program that was applied was the aerobic type of training. However, it is not the most effective type. Aerobic training in combination with endurance training proved to be the most effective type of training (Farris et al., 2011;Park et al., 2003;Meredith-Jones et al., 2009). It's a training method that lasts from 20 to 60 minutes, with low-intensity exercises and a heart rate zone of 50 to 75%. During such training, fats are mostly used as energy sources, which affects the reduction of body fat. However, such training can lead to a decrease in muscle mass, so it is combined with endurance training, which affects the increase in muscle mass (Rey et al., 2017).
The second most effective in combating obesity would be aerobic training alone. Aerobic physical activity is of low intensity and longer duration and as such provides energy without the appearance of lactic acids. Although this type had positive effect on weight loss, fat percentage and BMI, this phenomenon can lead to a decrease in muscle mass or a significantly smaller increase in muscle mass compared to other physical activity (Park et al., 2003).
And as the least effective types of training we are left with the remaining types such as strength training, endurance training, anaerobic training, high-intensity interval training. In all these studies, it was shown that they had a positive effect on reducing the fat percentage. However, these types of trainings are short, so the mechanism of using fat as an energy source is not activated, and primarily for these trainings is an increase in muscle mass, which is the reason for reducing the percentage of fat in the body. More precisely, the mass of adipose tissue itself changes very little, almost not at all (Meredith-Jones et al., 2009;Saif & Alsenany, 2015;Skrypnik et al., 2015). Based on the obtained results of previous research, it can be concluded that physical activities have a positive effect on obesity regardless of the age of the respondents. All types of training are used for both children and adults.