When we gain weight, the weight is usually put on in the form of fat. The exception to this general rule is when weight is gained in the form of muscle, usually by lifting weights or participating in other muscle building activity. Weight that is put on as fat can be distributed to different regions of the body. The two most common areas that fat can be stored is in subcutaneous fat or visceral fat. Subcutaneous fat is located directly underneath the skin. Visceral (belly fat), or intra-abdominal fat is located in the abdomen and it surrounds many vital organs such as the stomach, intestine, aorta, and liver.
It was once thought that all fat was the same and just utilized for energy storage. We now know that the location of fat deposits on the body is critically important to the influence that the fat will have on your health. Visceral fat (belly fat) is much more harmful to your health than subcutaneous fat. Belly fat is much more metabolically active and produces several appetite regulating hormones. One of these hormones is leptin, which signals to your brain and other organs that you have eaten enough and should stop eating. A second important hormone that is secreted by fat is adiponectin, which regulates the response of cells to insulin. Belly fat also produces inflammatory cytokines, such as tumor necrosis factor and interleukin-6, which cause chronic inflammation. Chronic inflammation is increasingly becoming viewed as a leading cause of cardiovascular disease, such as heart attack and stroke, and can accelerate the process of atherosclerosis (hardening of the arteries).
The location of belly fat is also an important factor in its influence of health. Visceral fat is located near the portal vein, which lead directly into the liver. As belly fat secretes hormones and inflammatory cytokine in the portal vein, the first organ that is influenced by them is the liver. As a result, the production of lipids such as fatty acids, triglycerides, and cholesterol in the liver is effected and can lead to elevation of these lipid molecules. Elevation of lipids can lead to progressive atherosclerosis and plaque deposition in the coronary and cerebral arteries that can lead to heart attack and stroke, respectively.
Belly fat also influences the response of cells to insulin, and can result in decreased effectiveness of insulin on controlling blood sugar levels. As the effectiveness of insulin decreases, a condition termed insulin resistance, the risk of type 2 diabetes increases. Insulin resistance is a direct precursor to the development of type 2 diabetes as well as the metabolic syndrome. Both type 2 diabetes and the metabolic syndrome increase the risk for cardiovascular disease and can accelerate the atherosclerotic process. Recent research has also shown that obesity can increase the risk of cognitive decline that is seen with older adults, such as mild cognitive impairment and dementia. In addition, it has recently been found that belly fat increases the heart disease even in normal weight individuals.
The good news is that with weight loss and decreasing belly fat, blood pressure improves, cholesterol and other lipid parameters improve, and chronic inflammation decreases. Limiting processed high glycemic index foods, such as pasta and bread, can help decrease insulin levels and fat accumulation in visceral fat deposits. With weight loss and regular exercise, we can limit the negative influence of belly fat on our health and improve our cardiovascular risk profile. The World Health Organization recommends 150 minutes of moderate intensity exercise per week for healthy adults. We should all strive to obtain this level of activity to limit visceral fat accumulation and its negative health effects.
S. Girgis, MD