Rising trends in obesity prevalence among Royal Thai Army personnel from 2017 to 2021

Obesity is an essential health issue leading to noncommunicable diseases (NCDs) as well as atherosclerotic cardiovascular diseases. We aimed to determine the trends in obesity prevalence among Royal Thai Army (RTA) personnel and their associated factors using the health examination of RTA personnel database. A series of cross-sectional studies were conducted from 2017 to 2021. A self-report guide was created using a standardized case report form to obtain demographic characteristics and determine behavioral risk factors. Obesity was defined as BMI \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\ge$$\end{document}≥ 25 kg/m2, and a total of 512,476 RTA personnel nationwide were included. Obesity prevalence rose from 42.1% (95% CI 41.7–42.4) in 2017 to 44.2% (95% CI 43.9–44.5) in 2021 (p for trend < 0.001). A significant surge was observed in obesity prevalence among young RTA personnel aged 18–24 years from 23.7% in 2017 to 28.4% in 2021 (p for trend < 0.001). Higher age individuals, male participants and RTA personnel residing in Bangkok tended to have a significantly higher risk for obesity. Further, regular exercise was a protective factor for obesity. Our data emphasized that obesity among the RTA personnel has been continuously rising over one half-decade, especially among young adults.


Results
Demographic characteristics. A total of 512,476 RTA personnel were included in the study from 2017 to 2021. Demographic data of participants are presented in Table 1. The average age of participants was 38.2 ± 11.4 years. In all, 467,780 participants (91.3%) were males. One third of all participants resided in the central region. Almost all participants were under the Civil Servant Medical Benefit scheme, approximately 98%. The prevalence of current smokers was 28.5% in 2017 while it reached 33.3% in 2021. In terms of alcohol consumption, approximately two thirds of participants were current drinkers over 5 years. Participants with a history of regular exercise were 39.2% in 2017, and rose to 47.3% in 2021. The average BMI of participants was 24.7 ± 3.7 kg/m 2 in 2017, 24.8 ± 3.8 kg/m 2 in 2018, 24.9 ± 3.8 kg/m 2 in 2019, 24.9 ± 3.9 kg/m 2 in 2020 and 25.0 ± 3.9 kg/m 2 in 2021. www.nature.com/scientificreports/ 2021. Furthermore, the prevalence of RTA personnel having BMI ≥ 35 kg/m 2 was continuously incremental from 1.3% in 2017 to 1.8% in 2021. Figure 1 demonstrates the proportion of BMI groups among RTA personnel from 2017 to 2021. From 2017 to 2021, the overall obesity prevalence among RTA personnel increased significantly by the year of the study. www.nature.com/scientificreports/ ages 18 to 49 years significantly rose from 2017 to 2021 (p for trend < 0.05); moreover, a dramatic increase was noted in obesity prevalence among young RTA personnel aged 18 to 24 years by 4.7% over one half-decade (p for trend < 0.001). In terms of geographic region, obesity prevalence among RTA personnel residing in all regions, except in the south, significantly increased over five years (p for trend < 0.05).

Associated factors of obesity among RTA personnel. Univariable and multiple logistic regression
analyses were performed to determine the associated factors of obesity among RTA personnel ( Table 3). The  . Regarding behavioral factors, ex-smokers were more likely to be obese compared with participants who never smoked (AOR 1.14; 95% CI 1.12-1.16) while no association was observed between alcohol consumption and obesity. Moreover, RTA personnel who regularly exercised were at a significantly lower risk of obesity (AOR 0.82; 95% CI 0.81-0.83) than those having no history of regular exercise.

Discussion
To our knowledge, this study represented the largest epidemiologic study of obesity prevalence and its associated factors among RTA personnel in Thailand over one half decade. These data provide crucial evidence of rising trends in obesity prevalence among RTA personnel from 2017 to 2021. Factors associated with obesity included being male, higher age, geographic region, smoking status and no regular exercise. The average BMI among RTA personnel ranged from 24.7 in 2017 to 25.0 kg/m 2 in 2021 increasing at an average of 0.6 kg/m 2 per decade. This finding was comparable with the trends in adult BMI in a pooled analysis of 1698 population-based measurement studies from 200 countries 10 . Compared with the related study among Iranian military personnel, obesity prevalence in the current study was relatively high 11 . The present study reported the overall obesity prevalence among RTA personnel rose by 2.1% over five years which was compatible with the civilian trends in Thailand showing an increasing obesity prevalence from 37.5 in 2014 8 to 42.2% in 2019 12 . Similarly, a related study among active-duty military personnel in the US illustrated that combined overweight and obesity (BMI ≥ 25 kg/m 2 ) continuously increased from 50.6% in 1995 to 60.8% in 2008 13 .
Several studies have indicated that obesity prevalence among females was relatively high when compared with that among males 6,8,10,12 . In this study, male participants tended to present a higher risk for obesity approximately twice that of females corresponding to the obesity situation among military personnel in the US in that overweight and obesity prevalence among males was significantly higher 13 .
The present study emphasized that a significant rising obesity prevalence among RTA personnel aged 18 to 49 years over 5 years, especially among young RTA personnel aged 18 to 24 years, surged from 23.7 to 28.4% over one half decade. However, among older age groups, a deceleration was observed of rising obesity prevalence during the study period. Correspondingly, the NHES V and VI surveys showed rising trends in obesity prevalence in a Thai population aged 15 to 29 years approximately 7% over 5 years while remaining relatively lower among older Thai adults 8,12 . In addition, one study in the US demonstrated active-duty military personnel aged less than 25 years having BMI ≥ 25 kg/m 2 rose by approximately 8.6% from 1995 to 2008 while it remained slowly incremental among those with higher age 13 . This could be due to the transformation of Thai society to being www.nature.com/scientificreports/ more industrial; thus, fast food and high-energy food is more available 4,14 . The dietary behavior and lifestyle of young adults may facilitate increasing BMI in this age group. The current study presented that higher age participants tended to have obesity as a dose-response relationship, peaking at 40 to 44 years and dropping at age ≥ 50 years. This pattern was consistent with related studies in the US and China illustrating that obesity prevalence was greater among middle-aged individuals and declined among older people 13,15 . This phenomenon may be explained by reduced lean muscle mass associated with higher age 16 .
We found that the RTA personnel residing in Bangkok and the central region were inclined to exhibit obesity when compared with those in other regions. This occurrence was similar to a recent report that the BMI level of people residing in Bangkok and the central region of Thailand was relatively high 17 . In this area, several agriculture businesses facilitate more than sufficient dietary products combined with inappropriate patient dietary behaviors that might have encouraged increasing weight 17 . In addition, the NHES VI survey in 2019 reported the proportion of Thai populations aged ≥ 15 years in Bangkok and the central region consuming fast food was relatively high when compared with those in other regions. Moreover, Thais in Bangkok and the central region consumed less dietary fiber including fruits and vegetables among both males and females 12 . Table 3. Univariable and multivariable analysis of the association between demographic and behavioral factors and obesity prevalence among RTA personnel (2017-2021). OR odds ratio, CI confidence interval.

Variables
Unadjusted OR (95% CI) p-value Adjusted OR (95% CI) p-value www.nature.com/scientificreports/ Our study reported that ex-smokers were inclined to exhibit obesity. Related evidence indicated that weight gain usually occurred after smoking cessation leading to declined metabolic rate, increased caloric intake and changes in food preferences 18 . Furthermore, one related study in the US reported that weight gain among smokers who quit was more than that gained among current smokers, approximately 4.4 kg among males and 5.0 kg among females over a 10-year period 19 . Conversely, a recent study reported that smoking status was unassociated with obesity 4 . However, the finding was outweighed by the advantages of smoking cessation, which are much greater than the superfluous risk granted by the weight gain.
Finally, we found that regular exercise was a protective factor for obesity among RTA personnel similar to a related study among young Thai men 4 . Therefore, our study suggested that regular exercise, such as increased physical activity, running and weight training, should be encourage among RTA personnel to decrease BMI and alleviate the progression of NCDs including ASCVD 20,21 . However, the intensity of exercise should be modified appropriately for personal characteristics, especially among individuals with heart disease and elderly people 22,23 . Our findings emphasized that modifiable risk factors for obesity such as no regular exercise should be improved among RTA personnel. Among young RTA personnel ages 18 to 24 years, obesity prevalence speedily rose over five years; therefore, health interventions including raising awareness regarding reducing their weight and associated further complications such as T2D and HT, should be facilitated in these age groups. Further, modifying dietary behaviors and regular self-weighing can also play an essential role to control BMI level [24][25][26] .
Several limitations were encountered in this study. First, the study employed a serial cross-sectional design; therefore, the results could demonstrate only the association between factors and outcomes. Second, the present study was conducted among RTA personnel comprising a greater proportion of male participants accounting for 91.3%; however, the results reported the real situation in this study population. According to the observational study using the health examination database, behavioral risk variables were collected very broadly, e.g., total number of alcohol drinks, total number of cigarettes and smoking frequency and intensity of exercise were not recorded. However, the associations between factors and outcomes were able to be presented. Our study also exhibited significant strengths, including a representative, large sample of RTA personnel. Thus, our findings provided valuable insights regarding the prevalence, demographics and behavioral risk factors of obesity in Thailand. Furthermore, these data may contribute to strategies for the primary prevention of metabolic syndrome, T2D, HT and ASCVD in this population.

Conclusion
Our data emphasized that obesity among RTA personnel has been continuously rising from 2017 to 2021, especially among young adults. RTA personnel residing in Bangkok and the central region tended to present a greater obesity prevalence. Regular exercise should be encouraged to alleviate the process of obesity, and dietary behaviors should be modified concurrently.

Data availability
Data cannot be shared publicly because the data set contains identifying information; additionally, the data belong to the Royal Thai Army Medical Department. Thus, ethics restrictions exist concerning the data set. Data are available from the Royal Thai Army Medical Department, Bangkok, Thailand for researchers meeting the criteria to access confidential data.