Being physically fit is very much better for long term health than being unfit. But in this era of cheap and attractive calories, it is quite possible to be both physically fit and overweight to some degree. Many people are. Unfortunately, being fit doesn't meaningfully protect against the detrimental effects of excess fat tissue on health and disease risk. If you are carrying more visceral fat tissue, then you have a higher risk of all of the common age-related diseases, when compared with someone of the same level of fitness with less visceral fat tissue.
Not so many years ago, metrics based on the ratio of height to waist circumference - such as the simple waist-stature ratio - began to appear in epidemiological studies as a replacement for the time-worn use of body mass index. The waist-stature ratio correlates more closely than body mass index with risk of disease, mortality, and other unfortunate aspects of aging. This points to the importance of visceral fat in disease processes. Even so it will take some time to percolate through the research community. Epidemiology doesn't move rapidly, and older data sets often lack the necessary information for use of waist-stature ratio, while most include body mass index.
How does visceral fat cause harm over the long term? Chronic inflammation is likely the primary mediating mechanism. Visceral fat cells are metabolically active, and when present in large numbers secrete signals that rouse the immune system. In addition, excess visceral fat appears to generate senescent cells at an accelerated rate, and these also secrete a mix of molecules that cause chronic inflammation. Fat cell debris further contains DNA fragments that aggravate the immune system in a different way. The inflammation generated by fat tissue disrupts processes of regeneration, and accelerates the progression of age-related diseases such as atherosclerosis and dementia.
Researchers have found that physically active men who were not overweight but whose waist-stature ratio (WSR) was close to the risk threshold were also more likely to develop heart disorders than individuals with lower WSRs. Recent research suggests that the WSR (waist circumference divided by height) is a more accurate predictor of cardiovascular risk than the body mass index (BMI), a widely used measure of body fat.
The researchers further investigated this hypothesis by analyzing the autonomic recovery of heart rate after aerobic exercise in healthy men with different WSRs. To this end, 52 physically active healthy men aged 18-30 were divided into the following three groups according to WSR: between 0.40 and 0.449, which is below the risk threshold for cardiovascular disease; between 0.45 and 0.50, which is close to the threshold; and between 0.50 and 0.56, which is above the threshold. The participants were tested on two separate days with a 48-hour interval between the two tests. Their heart rate and heart rate variability were measured while at rest and six times during a recovery hour to assess their speed of autonomic recovery after physical activity.
Analysis of the measurements showed that the autonomic recovery was slower in the groups with WSRs close to and above the risk threshold for heart disease after both the maximum effort test and moderate aerobic exercise. "We found that volunteers in the group with WSRs close to the risk limit were also more likely to develop cardiovascular disorders." The results of the statistical analyses suggested that two factors were most significantly correlated during the first ten minutes of the postexercise recovery period, when the parasympathetic nervous system (PNS) was being reactivated. Among other functions, the PNS, one of the three divisions of the autonomic nervous system, slows heart rate, and reduces blood pressure via the release of hormones.
Amongst the indicators of abdominal obesity, body mass index (BMI), waist circumference (WC), hip circumference (HC), conicity index (CI), waist-stature ratio (WSR) have been studied and are widely accepted in disease assessment, management and predictions in clinical practice and public health surveillance. Lately, WSR has been widely applied as it is simple, easy to measure and calculate. It is obtained by dividing the WC by height, in which WC demonstrates abdominal obesity and height remains constant in adults, which allows the possibility for direct comparisons in the general population.
Although the research literature has focused on obese patients with increased risk based on the WSR, it lacks evidence in subjects with values closer to the limit, herein moderate risk. In this sense, we appraised autonomic recovery after aerobic exercise in healthy men with different ranges of WSR. We found that healthy men with higher WSR accomplished delayed autonomic recovery following maximal effort exercise. Our results draw attention to the importance of cardiovascular prevention in the population within WSR values above 0.45, since we established that physically active men in this group offered slower autonomic recovery following aerobic exercise.