This popular science article takes a high level look at the vast array of research data showing that excess visceral fat causes great harm to long term health. One of the more important mediating mechanisms is an increase in chronic inflammation, a state of dysfunction in the operation of the immune system that disrupts organ function and tissue maintenance, and accelerates the development of all of the common age-related diseases. There are numerous other connections between the pace of aging and the activities of visceral fat tissue, however. Becoming overweight is the path to a shorter life expectancy, greater incidence of age-related disease, and higher lifetime medical expenditures.
In general, if your waist measures 35 or more inches for women or 40 or more inches for men, chances are you're harboring a potentially dangerous amount of abdominal fat. Subcutaneous fat that lurks beneath the skin may be cosmetically challenging, but it is otherwise harmless. However, the deeper belly fat - the visceral fat that accumulates around abdominal organs - is metabolically active and has been strongly linked to a host of serious disease risks, including heart disease, cancer, and dementia. Weight loss through a wholesome diet and exercise - activities like walking and strength-training - is the only surefire way to get rid of it.
Unlike the cells in subcutaneous fat, visceral fat is essentially an endocrine organ that secretes hormones and a host of other chemicals linked to diseases that commonly afflict older adults. One such substance is called retinol-binding protein 4 (RBP4) that was found in a 16-year study of nurses to increase the risk of developing coronary heart disease. This hazard most likely results from the harmful effects of this protein on insulin resistance, the precursor to type 2 diabetes, and development of metabolic syndrome, a complex of cardiac risk factors.
The Million Women Study conducted in Britain demonstrated a direct link between the development of coronary heart disease and an increase in waist circumference over a 20-year period. Even when other coronary risk factors were taken into account, the chances of developing heart disease were doubled among the women with the largest waists. Every additional two inches in the women's waist size raised their risk by 10 percent.
Cancer risk is also raised by belly fat. The chances of getting colorectal cancer were nearly doubled among postmenopausal women who accumulate visceral fat, a Korean study found. A Dutch study published last year linked both total body fat and abdominal fat to a raised risk of breast cancer. When the women in the study lost weight - about 12 pounds on average - changes in biomarkers for breast cancer, like estrogen, leptinm and inflammatory proteins, indicated a reduction in breast cancer risk.
Perhaps most important with regard to the toll on individuals, families and the health care system is the link between abdominal obesity and risk of developing dementia decades later. A study of 6,583 individuals in Northern California who were followed for an average of 36 years found that those with the greatest amount of abdominal obesity in midlife were nearly three times more likely to develop dementia three decades later than those with the least abdominal fat.
Over all, according to findings among more than 350,000 European men and women published in The New England Journal of Medicine, having a large waist can nearly double one's risk of dying prematurely even if overall body weight is normal.