There's been a lot of press coverage recently of a natural substance called- and the potential health and fitness benefits it may hold.
A number of studies have been done on this compound, and the list of positive effects are impressive.
Ursolic Acid is believed to:
Reduce fat storage and increase fat burning, through inhibition of pancreatic lipase and lipolysis in fat cells. 
Reduce the conversion of blood sugar to fat, through inhibition of fatty acid synthase. 
Increase energy reserves in muscles by enhancing glycogen storage. 
Reduce abdominal (visceral) fat through the inhibition of 11bHSD1. 
Be anti-carcinogenic through inhibition of the STAT3 activation pathway. 
Lower cholesterol through the activation of peroxisome proliferator-activated receptor (PPAR)-α. 
Reduce estrogen levels through aromatase inhibition. 
Strengthen bones by enhancing differentiation and mineralization of osteoblasts. 
Increase lean through enhanced sensitivity to and insulin and inhibition of atrogin-1 and MuRF1. 
Always make sure you buy a high quality ursolic acid supplement like E-Pharm Ursobolic.
Apple peel helps build muscle and control weight - Daily Mail
An apple a day keeps your body toned and slender - Telegraph
Can a compound in apple peel help build muscle? - Health News - NHS Choices
Ursolic acid: apple anabolic - Ergo-Log
 Arch Pharm Res. 2009 Jul;32(7):983-7.
Anti-lipase and lipolytic activities of ursolic acid isolated from the roots of Actinidia arguta.
 Biochem Biophys Res Commun. 2010 Feb 12;392(3):386-90.
Evaluation of inhibition of fatty acid synthase by ursolic acid: positive cooperation mechanism.
 Issled. Mekh. Vliyaniya Bal'neol. Faktorov Regul. Sist. Org. (1976), 101-2.
Effect of ursolic acid on the energy and carbohydrate metabolism of muscles
 Bioorg Med Chem. 2010 Feb 15;18(4):1507-15.
11beta-Hydroxysteroid dehydrogenase 1 inhibiting constituents from Eriobotrya japonica revealed by bioactivity-guided and computational approaches.
 Mol Cancer Res. 2007 Sep;5(9):943-55.
Ursolic acid inhibits STAT3 activation pathway leading to suppression of proliferation and chemosensitization of human multiple myeloma cells.
 Bioorg Med Chem Lett. 2011 Oct 1;21(19):5876-80.
Ursolic acid is a PPAR-α agonist that regulates hepatic lipid metabolism.
 Eur J Med Chem. 2008 Sep;43(9):1865-77.
Evaluation of ursolic acid isolated from Ilex paraguariensis and derivatives on aromatase inhibition.
 Pharmacol Res. 2008 -Dec;58(5-6):290-6.
Anabolic activity of ursolic acid in bone: Stimulating osteoblast differentiation in vitro and inducing new bone formation in vivo.
 Cell Metabolism. Volume 13, Issue 6, 8 June 2011, Pages 627-638
mRNA Expression Signatures of Human Skeletal Muscle Atrophy Identify a Natural Compound that Increases Muscle Mass