There are two main types of body fat: subcutaneous, the protective and relatively harmless layer of fat underneath the skin, and visceral fat, which surrounds body organs deep within the abdomen and, in excess, can trigger inflammation and lead to metabolic syndrome and type 2 diabetes.
Metabolic syndrome is a combination of abnormal physical conditions including high levels of bad cholesterol and low levels of good cholesterol, excess fat around the waist, elevated blood pressure and blood sugar, insulin resistance, chronic inflammation, and excess uric acid in the blood. When some or all of these factors combine, chances for heart disease and type 2 diabetes rise.
Participants in this study weighed at least 350 pounds, were not pregnant, did not have cardiovascular disease, and had normal kidney function. As blood levels of vitamin D rose, waist size and insulin levels fell.
Researchers found the strongest link between high levels of visceral fat and low levels of vitamin D, which they concluded could contribute to insulin resistance and metabolic syndrome.