Lipitor is a brand name for the drug atorvastatin, which is a medication used to lower cholesterol levels in the body [1]. The drug works by inhibiting an enzyme called HMG-CoA reductase, which is responsible for producing cholesterol in the liver [2]. By inhibiting this enzyme, Lipitor reduces the amount of cholesterol produced by the liver and increases the liver's ability to remove LDL cholesterol from the bloodstream [3].

The study published in PubMed [2] explains that Lipitor also alters fat metabolism by increasing the activity of an enzyme called lipoprotein lipase (LPL). LPL is responsible for breaking down triglycerides (a type of fat) in the bloodstream and storing them in fat cells. By increasing LPL activity, Lipitor can increase the rate at which triglycerides are broken down and stored, leading to a decrease in triglyceride levels in the bloodstream [2].

The FDA label for Lipitor [3] also notes that the drug can cause changes in lipid metabolism, including a decrease in total cholesterol, LDL cholesterol, and triglycerides, as well as an increase in HDL cholesterol (the "good" cholesterol). The label also notes that Lipitor can cause changes in liver function tests, so patients taking the drug should have their liver function monitored regularly [3].

In summary, Lipitor alters fat metabolism by inhibiting the production of cholesterol in the liver and increasing the breakdown and storage of triglycerides through increased LPL activity. This leads to a decrease in total cholesterol, LDL cholesterol, and triglycerides, and an increase in HDL cholesterol. However, patients taking Lipitor should have their liver function monitored regularly due to potential changes in liver function tests [2][3].

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://pubmed.ncbi.nlm.nih.gov/23959724/
[3] https://www.accessdata.fda.gov/drugsatfda_docs/label/2009/020702s057lbl.pdf