GW501516 (also known as GW501, GW516, GW1516) belongs to family of drugs that act on the PPARD receptors and is an oral drug that is bioactive (has interaction with or effect on cell tissue) in humans.
PPARD is believed to work at the gene level and affects skeletal muscle metabolism. In one laboratory study, PPARD activation seemed to nearly double the Performance of running endurance in untrained adult mice.

Other potential functions of GW501516 include its regulation of fat metabolism, glucose uptake in skeletal muscle tissue and an increase in muscle gene expression.
The combined effects of these various functions suggest it has a role in burning fat for energy instead of carbohydrates or muscle protein.
As such, it fits within an area of research into clinical applications for obese patients to lose fat effectively without experiencing muscle catabolism or the effects and satiety issues associated with low blood sugar.
In studies on mice, GW501516 led to increases in muscle mass, which improved glucose tolerance and reduced fat mass accumulation even in mice fed a very high fat diet.

Abstract: We evaluated the effects of GW501516, a specific peroxisome proliferator-activated receptor β/δ (PPARδ) agonist in metabolic syndrome mice, obtained by perinatal injection of monosodium l-glutamate, to investigate the efficacy of GW501516 against metabolic syndrome and the effectiveness of PPARδ activation as therapeutic target for metabolic syndrome. After 14 days treatment, GW501516 effectively improved the glucose intolerance, normalized the fasted blood glucose, and increased the serum high-density lipoprotein cholesterol (HDL-C) level. Postprandial blood glucose, serum insulin, leptin, free fatty acid (FFA) levels, and total cholesterol/HDL-C ratio were also significantly decreased. Moreover, semiquantitative reverse transcription–polymerase chain reaction results indicated that the above phenotypes might be due to (i) enhancement of fatty acid oxidation in muscle, adipose tissue and the liver; (ii) improvement of insulin-stimulated glucose transportation in skeletal muscle and adipose tissue; and (iii) reduced local glucocorticoid synthesis. Therefore, GW501516 could significantly ameliorate dyslipidaemia and insulin resistance in monosodium l-glutamate mice and activation of PPARδ could be envisioned as a useful strategy against human metabolic syndrome and related diseases.