Context: Deciphering the early processes occurring in adipose tissue during weight gain is a major issue for understanding the development of fat mass and obesity. Experimental overfeeding in humans is a unique situation to tackle these events. Objective: Our aim was to identify the pathways involved in sc adipose tissue remodeling during the initial phase of weight gain. Research Design and Methods: Forty-four healthy men were involved in an overfeeding protocol with a lipid-enriched diet (+ 760 kcal/d) for 2 months. Subcutaneous abdominal adipose tissue biopsies were taken for histology, transcriptomics, and Western blotting in the basal state, after 14 d, and at the end of the protocol. Results: Overfeeding significantly increased body weight (+ 2.5 kg) and fat mass. Reorganization of gene expression patterns occurred in adipose tissue with an up-regulation of numerous genes involved in lipid metabolism and storage, followed by clusters of genes related to angiogenesis and extracellular matrix remodeling. Histological examination showed increased microvascular density and connective tissue deposition after 56 d of overfeeding, with no changes in the number of macrophages or inflammatory cells. Inhibition of the canonical Wnt/beta-catenin signaling pathway and induction of the renin-angiotensin system might be implicated in the remodeling of sc adipose tissue. Conclusions: We characterize the coordinated and time-dependent processes that occur in human adipose tissue during the early phase of weight gain in healthy subjects and identify pathways representing potential targets in pathologies of adipose development, including obesity. (J Clin Endocrinol Metab 97: E183-E192, 2012)