Of the 30 participants with at least one risk factor who were included in the nutritional intervention, only 18 attended the evaluative measurement. The significant decrease in the number of participants in the evaluative measurement may be attributed to a lack of awareness regarding the importance of controlling and addressing identified risk factors. It is also possible that participants did not adhere to the advice given during the nutritional intervention and believed there was no need for retesting. This is supported by data showing that the majority of participants included in the evaluative measurement claimed to fully or partially adhere to the advice received during the nutritional intervention.
During the initial assessment, half of the participants reported having breakfast every day, while a quarter irregularly ate breakfast. Most participants had lunch daily, and a third of them had snacks every day. Half of the participants regularly had dinner. On the evaluative assessment, most participants had breakfast five to seven days a week (p=0.039). This result might suggest that participants who regularly had breakfast earlier were more likely to attend the evaluative measurement, but it could also be an outcome of the nutritional intervention. According to data from the Institute of Public Health of Serbia, the majority of the adult population in Serbia has breakfast every day [7].
Regarding the intake of specific food groups, one-third of participants consumed fruit at least once a day. On the evaluative measurement, most participants consumed fruit every day. Vegetables were consumed every day by about one-third of participants, but another third stated that they consumed vegetables only a few times a week. These data differ from the population data from the Institute of Public Health of Serbia, which indicates that half of the adult population in Serbia consumes vegetables daily, and slightly over a third consumes fruit daily [7]. Statistically significant differences in the frequency of vegetable consumption were observed in the evaluative assessment (p=0.039) compared to the initial measurement. Most participants included in the evaluative measurement reported consuming vegetables daily. Nutritional counseling aimed at increasing vegetable intake, suggesting that nutritional counseling contributed to the increased consumption of vegetables. It is also possible that participants who already had a habit of consuming vegetables daily attended the evaluative measurement.
Added sugars were present in the diet of almost half of the participants for five to seven days a week. Carbonated sweetened beverages were consumed almost daily by one-fifth of the participants. Foods rich in added salt (salty snacks) were regularly consumed by 16% of participants. Most participants stated that they drank caffeinated beverages every day. Nearly half of the participants reported consuming alcoholic beverages on a monthly basis, while 14% stated that they consumed alcoholic beverages more than once a week. A statistically significant difference in the distribution of participants based on alcohol intake was observed on the evaluative measurement (p=0.443). No participants reported consuming alcoholic beverages five to six times a week, but compared to the initial measurement, more participants reported consuming alcoholic beverages two to four times a week. It is possible that some participants reduced their alcohol intake after the nutritional intervention, but it is also possible that participants who are more conscientious about alcohol intake attended the evaluative measurement.
The presented results related to dietary habits confirm that changing dietary habits is challenging because it requires initiating a whole set of internal factors (awareness, motivation) and external factors (changes in family dietary patterns, food availability, cooking skills) for lasting and profound changes in dietary habits [26]. Considering that some data related to the participants' diet in the evaluative measurement were more favorable compared to the initial measurement, it is possible that participants who were motivated to make certain changes in their diet for health improvement attended the evaluative measurement.
Two-thirds of the participants in this study are overweight, with an average BMI of 28 kg/m2. Only a third of the participants have a normal weight, and only a quarter of them do not have visceral obesity. These results are in line with the data from the Institute of Public Health of Serbia on the health of the population of Serbia from 2019, which indicates that over half of the adult population (57.1%) is either overweight or obese [7]. Undesirable statistically significant changes in the distribution of participants regarding nutritional status occurred in the evaluative measurement. 48% of participants included in the evaluative measurement were overweight and obese. This data may suggest that predominantly participants who were already overweight and obese attended the evaluative measurement and were motivated to make certain changes in their diet.
Central obesity is a major component of MetS. Waist circumference shows a significant correlation with BMI, blood pressure levels, impaired glucose metabolism, and elevated serum triglyceride levels. Due to its simplicity and non-invasiveness, waist circumference is a convenient screening method for population studies [27]. The average waist circumference value in the evaluative measurement was slightly lower than in the initial measurement, although the difference was not statistically significant. The number of participants with waist circumference values in the category of high or extremely high risk decreased in the evaluative measurement. Taking into account the data on the nutritional status of participants included in the evaluative measurement, the result may suggest a reduction, although not statistically significant, in waist circumference values in certain participants.
The average blood pressure level at the initial and evaluative measurements was 129/82 mmHg. One-third of the participants had hypertension at the initial measurement. Significantly more participants with excessive body weight had hypertension (p=0.000; p=0.046). There were no significant changes in the distribution of participants according to blood pressure values in the evaluative measurement. Hypertension is a common companion of MetS and is present in almost 80% of people with MetS [27]. According to data from the Institute of Public Health of Serbia, almost half of the adult population in Serbia has hypertension [7]. To control hypertension, the American Heart Association recommends sodium intake < 1500 mg/day or < 3.75 g of salt per day along with physical activity lasting at least 150 minutes per week [28,29].
Advisory work directed at participants with hypertension was based on the basic principles of the DASH diet (Dietary Approaches to Stop Hypertension), which involves the consumption of fruits, vegetables, dietary fibers, especially nuts and legumes, and low-fat dairy products. A meta-study on the effects of the DASH diet on hypertension has shown that the DASH diet contributes more to reducing blood pressure values in individuals under 50 years of age and those not taking antihypertensive medications, as well as in the case of a significant reduction in sodium intake below 2.4g per day [30]. One possible explanation for the lack of significant changes in blood pressure values after nutritional intervention is that, in the initial measurement, 13% of participants reported already using medication for hypertension.
The average blood sugar level of participants at the initial measurement was 5.6 mmol/l. Elevated blood sugar values at the initial measurement were found in 13% of participants, and this was statistically significantly more common in participants with excessive body weight (p=0.001) and elevated waist circumference values (p=0.003). This result is expected given that individuals who are overweight and obese, especially if it is central obesity, have a higher risk of glucose metabolism disorders [31]. In the evaluative measurement, the average blood sugar value did not significantly differ from the initial measurement. Most participants included in the evaluative measurement had optimal blood sugar values, although there were no significant differences in the distribution of participants according to blood sugar values compared to the initial measurement. This result may suggest that participants with elevated blood sugar values did not participate in the evaluative measurement, but it may also mean that a certain number of participants had their blood sugar values corrected due to dietary changes.
The average cholesterol level at the initial measurement was 5.7 mmol/l. In the evaluative measurement, the average cholesterol value was significantly lower at 5.4 mmol/l (p=0.005), although both values correspond to borderline elevated cholesterol levels. Elevated cholesterol levels at the initial measurement were found in almost three-quarters of participants, and nearly half of the participants had extremely elevated cholesterol values. In the evaluative measurement, there were significant changes in the distribution of participants according to cholesterol values (p=0.002). Approximately the same number of participants included in the evaluative measurement had normal and elevated cholesterol values, but the number of participants with extremely elevated and values exceeding the measurement range of the device was lower compared to the initial measurement. This result may indicate a reduction in cholesterol values after nutritional intervention, but it may also mean that a certain number of participants with elevated cholesterol values did not participate in the evaluative measurement.
HDL-cholesterol is a significant protective factor in preventing cardiovascular diseases, preventing the formation of adhesive endothelial molecules, and having anti-inflammatory effects. On the other hand, a high level of LDL-cholesterol significantly affects increased cardiovascular mortality [32]. Reducing LDL-cholesterol by 1 mmol/l reduces the five-year cardiovascular mortality by one-fifth, and reducing it by 2-3 mmol/l reduces this risk by 40-50% [6, 33, 34].
The average triglyceride level at the initial measurement was 2.3 mmol/l, while in the evaluative measurement, the average triglyceride level was 2.2 mmol/l. Both values correspond to extremely elevated levels. Elevated triglyceride levels were identified in more than half of the participants, while more than a third of the participants had extremely elevated triglyceride values at the initial measurement. A positive correlation was found between triglyceride levels and the age of participants (p=0.028), hyperglycemia (p=0.029), and systolic hypertension (p=0.046). After nutritional intervention, there were no significant changes in triglyceride values. Regarding fats, during nutritional intervention, participants were advised to increase the intake of monounsaturated and polyunsaturated fatty acids from fish, olive oil, nuts, and limit the intake of saturated fats from animal-derived foods, coconut and palm oil, as well as trans fats [35,36].
Early recognition and correction of risk factors that make up MetS are extremely important for preventing cardiovascular diseases and type 2 diabetes mellitus. In this study, it was found that over a third of participants had three or four present risk factors, which are diagnostic criteria for MetS, while a third had two risk factors. After nutritional intervention, there were no significant changes in the distribution of participants according to the number of risk factors. In the evaluative measurement, most participants had one or two risk factors, and no participant had four risk factors. A study conducted in Hungary in 2019 found the presence of MetS in 72% of adult participants, more often in women [6]. A higher incidence of MetS in women was also observed in Croatia [37].
When interpreting the results of this study, it is essential to consider its limitations. The study was conducted on a small number of participants from a single institution, and the results may not be representative of the working population in Subotica. Due to the disproportionate number of female and male participants, it was not possible to determine differences in the observed variables by gender. Biochemical parameters were determined from capillary blood, not serum. Hypercholesterolemia was considered a confirmed risk factor. Since data collection was based on rapid and minimally invasive techniques for assessing biochemical parameters, the study considered the total cholesterol value without additional information about the levels of individual lipid fractions. Measurement errors could result from the limitations of the measurement equipment or inadequate participant preparation. Clear effects of nutritional intervention on changes in metabolic syndrome parameters cannot be fully assessed due to the lack of a control group and the small number of participants included in the evaluative measurement.