This study is a phase I, randomized, placebo-controlled, double-blind (sponsor unblind), three part study. The primary objective of the study is to characterize the safety, and tolerability of GSK3008356 single dose, 14 daily repeat doses in healthy subjects and 28 daily repeat doses in obese subjects. The study has three parts. Part 1, will be a single and multiple-dose, dose-rising study in healthy subjects. Part 2, will be a 14-day, repeat-dose, dose-rising study in healthy subjects, and part 3 will be a 28-day, repeat-dose study in obese subjects. For Parts 1 and 2, data from prior doses cohorts will be available prior to escalation decisions. Data from Parts 1 and 2 will be available prior to initiation of the three parallel cohorts in Part 3. A dose escalation meeting will be held to review these data and document the decision to proceed as planned or make any alterations in dosing, if indicated. Part 1, Part 2 and Part 3 study will have approximately 88, 24 and 30 subjects, respectively.