Each adipocyte cell has a large, central, uniform, lipid packed central vacuole which, as it enlarges, pushes all the cytoplasm, the nucleus and all the other organelles to the edge of the cell, making it look a bit like a band or ring under the microscope.
These cells can vary in size from about 30 microns to over 230 microns, and, despite their distorted appearance, contain all the necessary biochemical machinery of other cells.
Every adipose cell must touch at least one capillary or blood vessel (an artery or vein). From this the cells draw all their needed supplies, including lipids.
Fatty foods, with high lipid content, often provide more lipids than can be digested and used right away. The excess is stored in the adipose tissue. Excess carbohydrate and protein taken in with meals can also be converted to fat (usually in the liver) and then moved to the adipose tissue for longer-term storage.
Lipids are the major fuel reserve for humans and most mammals. These molecules are very efficient at storing needed energy. One gram of fat stores about 9 kcal per gram, compared to carbohydrate or protein (4 kcal per gram). For mobile animals, this means that less bulk has to be carried around and a normal sized body that is about 20% fat has enough stored energy to last about 20 30 days without eating!