Methods of modulating peroxisome proliferator-activated receptor a (PPARa) activity in a cell in a subject In need thereof are provided. The methods include administering an effective amount of a PPARa ligand to the subject where the PPARa ligand is selected from 3-hydroxy-2,2-dimethyl butyrate (HMB), hexadecananamide (HEX) and 9-octadecenamide (OCT), Methods of treating dementia, neurodegenerative disorders, lysosomal storage diseases and body weight disorders in a subject in need thereof are provided. The methods include administering an effective amount of a PPARa ligand to the subject.