The purpose of this study is to determine the effect of a 4-week treatment period with GW501516X on how the heart obtains and uses energy. The energy of the heart will be measured by Magnetic Resonance Imaging (MRI). This study will also measure a number of other potential markers of drug activity, including levels of certain lipids (fats) and proteins in your blood. The data from this study may help researchers better understand the actions of this drug in the body and if this drug may be useful to treat patients with heart disease.

Inclusion criteria:

• Non-smoking.
• Body Mass Index of greater than 27 and less than 32 and who weigh 120 kg (264 lbs) or less and have a waist circumference of greater than 95 cm (37.5 inches).

Exclusion criteria:

• History of muscle disease, coagulation disorders, heart disease or abnormal heart rhythm (or a family history of early coronary artery disease).
• Documented diabetes, hypoglycemia, thyroid disfunction or adrenal disorder.