In this study, we investigated the effects of BMI and muscle strength on risk factors for Mets and its prevalence in Korean adult women aged 19 years or older using data from the 2019 Korea National Health and Nutrition Examination Survey. The results showed that WC and TG were significantly lower, while HDL-C was significantly higher, in the high muscle strength group than in the low muscle strength group. The muscle strength was evaluated by measuring handgrip strength in this study. It has been reported that muscle strength assessed by handgrip strength is closely associated with the prevalence of and mortality from various diseases(36). In particular, it has been reported that the level of muscle strength is closely associated with risk factors for Mets(21), and that lower muscle strength increases the risk factors for Mets and mortality associated with Mets(20, 37). In addition, Agner et al., reported that high muscle strength is an important factor in lowering the risk factors and prevalence of Mets(38).
Ji et al., evaluated 2,521 women and analyzed the association between risk factors for Mets and muscle strength assessed by the relative handgrip strength according to body weight, after adjusting for age, race, drinking, smoking, education level, income, energy intake, and physical activity. As a result, when muscle strength was low, WC, TG, FG, SBP, and DBP were high. Also, HDL-C was low(39). In this regard, it is known that muscle strength is closely associated with muscle mass(40), and an increase in muscle mass can be improved through resistance exercise training; this indicates that increased muscle strength protects against the risk factors for Mets(19). Oliveira et al., reported that a 1-week resistance exercise training program had protective effects against total cholesterol (TC), TG, and WC in 22 menopausal women(41).
When subjects were stratified by BMI, we found that SBP, DBP, TG, and FG were significantly lower, while HDL-C was significantly higher, in the low BMI group than in the high BMI group. high BMI is negatively affects health and is known to be a major risk factor for various diseases, including Mets(42, 43). Balgoon et al., evaluated the association between BMI and risk factors for Mets in 165 women and reported that risk factors such as WC, SBP, and DBP were significantly higher in women with a high BMI (≥ 25 kg/m²) than in those with a low BMI (< 25 kg/m²), and that the risk of Mets increased with BMI(44). In addition, Choromańska et al., evaluated 44 women and reported that WC, BP, FG, and TG were significantly lower, while HDL-C was significantly higher, in non-obese women than in obese women with Mets. These results indicate that a high BMI negatively affects Mets and increases its prevalence(45). Therefore, adequate control of BMI can have protective effects against risk factors for Mets.
Finally, in this study, we found that WC, SBP, DBP, TG, and FG were significantly lower, while HDL-C was significantly higher, in subjects with low BMI and high muscle strength than in those with high BMI and low muscle strength. Moreover, the prevalence of Mets was 10.46 times higher in the high BMI & low muscle strength group than in the low BMI & high muscle strength group; after adjusting for age, menstruation status, and smoking, the prevalence was 7.38 times higher in the high BMI & low muscle strength group. Similarly, Lu et al., analyzed the risk of Mets development according to muscle strength and obesity after adjusting for age, sex, smoking, and drinking and reported that subjects with low BMI and obesity had an 11.93 times higher risk than did subjects with normal weight(46). In addition, Takayama et al., reported that the prevalence of Mets was 3.12 times higher in subjects with low muscle strength and high BMI than in those with normal muscle strength and weight after adjusting for age and sex(47). Song et al., evaluated the association between the prevalence of Mets and handgrip strength and investigated the prevalence of Mets according to handgrip strength and BMI in 542 elderly women. They found that with a decrease in handgrip strength and increase in BMI, there was a 2.25-fold increase in the prevalence of Mets. This study also showed that lower handgrip strength and a higher BMI were associated with a 2.12-fold increase in the prevalence of Mets after adjusting for age, smoking status, occupation, education level, family income, nutritional status, and physical activity(21). As such, it can be said that muscle strength and BMI have a strongly associated with Mets risk factors and prevalence. Therefore, it is thought that the prevalence of Mets can be lowered by lowering BMI through regular exercise and physical activity and increasing muscle strength through resistance exercise training.
This study has some limitations. First, because the subjects were only Korean adult women, the results cannot be generalized to adult women of different races and adult men. Second, because the subjects were aged ≥ 19 years, the results cannot be applied to adolescents and children aged < 19 years old. Third, because BMI levels was Asian standards (BMI ≥ 23kg/m²), the results cannot be extended to countries other than Asian countries. Fourth, BMI is calculated by dividing weight by the square meter of height (BMI = kg/m²) and is used as an indicator of obesity, but it is difficult to obtain accurate body composition including muscle. Finally, because this study determined the association of BMI and muscle strength based on handgrip strength with risk factors for Mets in Korean adult women, it is difficult to broadly apply the results to determine a causal association. Despite these limitations, this study is significant in that it comparatively analyzed a large number of samples using data from the first year of the 8th Korea National Health and Nutrition Examination Survey in 2019 and confirmed the effects of BMI and muscle strength based on handgrip strength on risk factors for Mets and its prevalence.