Final answer:
The process of an adipocyte filling with lipid and increasing its cell size is called lipogenesis.
Step-by-step explanation:
The process of an adipocyte filling with lipid and increasing its cell size is called lipogenesis. Lipogenesis is the process by which adipocytes synthesize and store triglycerides from fatty acids and glycerol. This filling of lipids in adipocytes leads to an increase in cell size, which is one of the mechanisms responsible for weight gain and obesity.