Differences in Cardiovascular Risk Factors and Upper and Lower Limb Muscle Function according to Waist to Hip Ratio Classification in Obese Women

Introduction

Obesity has been known to be one of the most important risk factors for inducing myocardial infarction, angina pectoris, and hypertension (Romero-Corral et al., 2006), suggesting that the diagnosis and evaluation of obesity are essential for a healthy life in modern people (Flegal et al., 2016).

Obese is categorized in various measurement index, which include body mass index (BMI), waist circumference (WC), waist-hip ratio (WHR), and body fat percentage(%BF). In clinical practice, the BMI is the most common method for diagnosing obesity, which was based on a person's weight in kilograms and height in meters. The Korea medical community has classified 18.6 and 22.9 kg/m² as normal BMI, 23 to 24.9 kg/m² as overweight, and 25 kg/m² and more as obese according to the Asia-Pacific criteria. However, as the obesity prediction methods by BMI has limitations in classifying obesity with high body fat mass and overweight with high muscle mass, the importance of classifying obesity using WHR has recently been emphasized (Lee et al., 2008). In a precious study of Janssen et al. (2002) that reported an association between WHR and obesity, an increase in abdominal adiposity had a more direct influence on cardiovascular disease than an increase in fat mass in other body parts. In addition, Schneider et al. (2010) suggested that WC and WHR were more accurate than BMI as predictive indicators of abdominal obesity in a study of 6355 obese subjects.

The world health organization (WHO) has provided guidelines for the optimal criteria for WHR to be 0.85 or less for women and 0.9 or less for men, because the women usually concentrate body fat mass on the hip and men accumulated on the waist. A WHR value of 1.0 or higher can induce cardiovascular and metabolic diseases as well as various complications related to obesity (Elsayed et al., 2008). In the field of exercise physiology studied on relationship between WHR and physical fitness in obese people, Correa-Rodríguez et al. (2018) provided some information that WHR and physical fitness have a high correlation and may be predictors of hypertension, diabetes, and cardiovascular diseases.

Recent studies have reported that obese people with high maximal oxygen uptake (VO₂max) have low WC and WHR, and show high physical fitness in push-ups, sit-up and vertical jump (Ekblom-Bak et al., 2009; Ortega et al., 2019; Ross & Katzmarzyk, 2003). But Lockie et al. (2020) highlighted that WC is most important indicator in predicting obesity because the physical fitness of obese people is further closely related to WC compared to WHR. To date, these previous studies reporting on physical fitness and WHR in obese are not clear. Therefore, it is necessary to confirm the relationship between physical fitness and cardiovascular disease based on WHR criteria in obese women. The purpose of this study was to investigate differences in cardiovascular disease risk factors and upper and lower limb muscle function according to the WHR classification in women with obese.

Methods

Results

Discussion

For decades, percent body fat and BMI has been widely used as an important marker of obesity in daily life and the medical community. But recently WHR or WHtR are found to be a clear indicator for diagnosing obesity (Pischon et al., 2008). In this study, we confirmed differences in body composition according to WHR classification in women with obesity and found that BMI value was significantly higher in the OHW compared to the NCG, but the free fat mass did not show a significant difference between all groups. In previous study of Jahanlou & Kouzekanani (2017) reporting the correlation between BMI and WHR in obese people, although WHR could influence BMI value, there was no interaction effect with FFM. These previous studies support our findings suggesting that WHR is a more important indicator than BMI for predicting obesity. However, we think that relationship between FFM and WHR needs to be systematically studied with more participants.

Obesity contributes directly not only to the pathogenesis of cardiovascular disease risk factors such as visceral adipose tissue, dyslipidaemia, diabetes and hypertension (Van Gaal et al., 2006) but also changes in metabolic syndrome risk factors including TC, TG, HDL-C, LDL-C and FG (Quijada et al., 2008). It has been well known that obese people with high WHR and WC values can be easily exposed to cardiovascular disease or metabolic syndrome (Gill et al., 2020). But, unlike previous studies, there was no statistically significant difference in cardiovascular disease risk factors in the present study. Considering these findings, the present study is inconsistent with previous study emphasized that obese people with high WHR value could be more likely to develop cardiovascular disease rather than obese people without abdominal adiposity (Hu et al., 2004). These contradictory findings in the present study are thought to be due to insufficient participants.

In addition, we confirmed that diastolic blood pressure was significantly upregulated in the OLW and OHW compared to the NCG. But this change in blood pressure is difficult to interpret because it is a difference within the normal range as well as we believe that this is because the subjects in the present study were healthy young women without any metabolic diseases.

Regular exercise is the most effective therapeutic method for preventing obesity and cardiovascular disease (Tian & Meng, 2019), and building up to vigorous level of physical fitness through exercise can bring about decrease of the WHR risk level in obese people (Söderlund et al., 2009). Taken together, these previous studies on exercise and obesity suggest that there may be a high correlation between physical fitness level and WHR in obese people. We investigated basic physical fitness and isokinetic knee and trunk muscle functions according WHR classification in obese women. As a result, we found that the lower extremity muscle function was significantly decreased in the OHW and OLW compared to the NCG. But maximal strength, flexibility, cardiorespiratory endurance, and trunk muscle function were no significant difference among groups. Lockie et al. (2020) reported that obese people with high-risk WHR cut-off value (0.85 or higher for women, 0.9 or higher for men) performed less muscular endurance, agility, and power capacity compared with obese people with low-risk WHR cut-off value (Masitoh et al., 2022). Also, Chen et al. (2020) reported that WHR might be better than BMI in measuring obesity-related decreased physical fitness. These results are consistent with the present results that high WHR values might decrease physical fitness in obese people.

Given these results reported in this study, if obese young women strive to maintain low WHR values, they may have improved health benefits over obese women with high WHR values through preventing decreases in physical fitness and lower extremity muscle functions.