We showed in the previous study that BFI was the best indicator of body fat in relation to the decrease in activity of the autonomic nervous system. [8] In this study, BFI correlated the most with total fat mass calculated as a percentage, rather than with BAI and BMI. BFI and BAI slightly correlated with waist size and triglycerides (TG). However, BFI showed a higher correlation with other bodily parameters from these two obesity indicators. Moreover, these two parameters, BAI and BFI, were more closely related to body fat, specifically compared to BMI which has frequently been used. For this reason, we can state that BFI and BAI would be two more suitable tools to characterize global obesity [9,10]. It is clearly well established that these indicators are associated with WC and TG. Conversely, BMI is more associated with all body components, not specifically to the fat contain. Thus, BMI in this regard cannot be considered as a reference parameter for identifying body fat.
In fact, overall and abdominal obesity as defined according to a BMI >30 kg/m2 and a WC greater than 88 or 102 cm take into account both the lean mass and fat mass. According to previous observations, it seems that BFI remains the best indicator to characterize the composition of body fat, while the BMI seems in relation to the overall weight.
All forms of obesity increase the risk of CVD and diabetes. [12,13] On the basis of the two previous studies [14,15], the authors proposed that the markers of a central-distributed obesity (in particular the W/H), in this case BAI or BFI in our context, would be more strongly linked to coronary artery disease (CAD) events as compared to BMI when used as a conventional measure.
Obesity represents an increasing public health problem all around the world. The incidence and the prevalence of obesity (estimation based on BMI values only) is higher in most developed countries and is the lowest in Asia. Previous studies have explored the relationship or association between BMI, waist-hip ratio or WC and CAD [5,15]. The results of these studies were contradictory some suggesting that BMI was better, if not a quite good marker for abdominal adiposity. Others authors have suggested that markers of abdominal obesity may be better predictive, in subpopulations of younger subjects and in women. Smaller previous studies also reported an opposed relationship between increased hip circumference and diabetes mellitus, systolic/diastolic hypertension, or dyslipidemia, and CVD [15,19]. Fat loss during weight loss is correlated with an increase in blood pressure and the worsening of metabolic risk factors [16,17,18]. These opposing (and perhaps paradoxical) effects of abdominal fat mass on cardiovascular disease risk can be explained in several ways. First, hormonal factors may impact waist circumference, thigh circumference and hip circumference differently. These same factors can also have a role on insulin resistance. For example, excess glucocorticoid production or growth hormone deficiency and high testosterone levels in women are frequently accompanied by an increase in visceral fat mass and a reduction in appendicular muscle mass. Similarly in men as well as low testosterone levels increase the level of insulin resistance [20].
Endogenous estrogens stimulate the accumulation of subcutaneous fat in the buttocks and thighs [19]. Furthermore, abdominal fat and fat accumulated in the lower part of the body have very different biochemical characteristics on the risk of developing cardiovascular diseases [21, 22]. This is related to a capacity in the secretion of adipokines (qualitatively and quantitatively) very different between these two types of fat [23].
An increase in gluteal muscle size could explain an increase in hip circumference and could represent a marker of overall skeletal muscle mass, an anthropometric parameter favorable to the reduction of insulin resistance for example. Furthermore, it is well recognized that a high WHR is usually associated with a relative reduction in muscle mass of the lower limbs and gluteal region [24]. A representative US cohort has demonstrated that appendicular muscle mass is a variable that modifies the relationship between BMI and mortality. Thus, it is advisable to further consider this adjustment variable to evaluate the deleterious effect of body fat mass in the epidemiologic assessment of cardiovascular risk. [25].
Thus, the ratio of fat mass to muscle mass (sarcopenic adiposity) may be a risk factor for CVD, particularly in the elderly. This type of sarcopenia with fatty infiltration of the vastus lateralis muscle (infiltrated adiposis droplets) has been found to be particularly frequent in elderly patients with metabolic syndrome in recent studies [26].