## 1 Introduction  
Obesity is caused by the excessive accumulation of internal fat from an imbalance between the body's energy intake and consumption. It can also act as a significant factor that increases the likelihood of chronic diseases, such as cardiovascular disease, type 2 diabetes, hyperlipidemia and high blood pressure [1]. Various obesity-related drugs have been developed to treat obesity, but these drugs can cause serious side effects [2; 3]. Therefore, there is a need to develop anti-obesity materials using natural products with fewer or no side effects that can potentially be useful for treating obesity [4; 5]. Adipocytes play an essential role in maintaining energy homeostasis and lipid metabolism. 3T3-L1, a pre-adipocyte, accumulates triglycerides, as it differentiates into an adipocyte by the action of various hormones and transcription factors. Preadipocyte differentiation, also known as adipogenesis, is regulated by essential transcription factors for adipogenesis, including CCAAT/enhancer-binding protein (C/EBP\(\alpha\)) and peroxisome proliferatorator-activated receptor gamma (PPAR\(\gamma\)). C/EBP\(\alpha\) and PPAR\(\gamma\) can activate adipocyte protein 2 (aP2), an adipose-specific gene [6; 7; 8]. The activation of late adipogenic factors is associated with triglyceride synthesis [9]. Sterol regulatory element-binding protein 1 (SREBP1) promotes the differentiation of preadipocytes into adipocytes. Additionally, it is an important transcription factor for enzymes that regulate triglyceride synthesis. Enzymes that synthesize triglycerides, such as lyso-phosphatidic acid acyltransferase theta (LPAAT0) and lipin 1, promote fat accumulation at the end of adipocyte differentiation [10; 11; 12]. The white adipose tissue (WAT) is the main energy store in mammals. Lipolysis is the hydrolysis of triglycerides stored in the WAT into diacylglycerols (DG), monoacylglycerols (MG), and glycerol. Each step releases one fatty acid molecule [13; 14]. Phosphorylation of protein kinase A (PKA) leads to the activation of lipolytic enzymes and lipolysis [15]. It is known that adipose triglyceride lipase (ATGL), phosphorylated hormone-sensitive lipase (p-HSL), and monoacylglycerol lipase (MGL) are three types of lipases that fully hydrolyze triglycerides in lipolysis. Regarding white adipose tissue and brown adipose tissue (BAT) in mammals, in comparison with the WAT, the BAT is enriched in mitochondria and has a characteristic protein termed as uncoupling protein 1 (UCP1). UCP1 can directly dissipate energy in the form of heat by oxidative uncoupling of fatty acids during adenosine triphosphate (ATP) synthesis. BAT promotes non-shivering thermogenesis through UCP1, thus playing a unique role in energy consumption. Therefore, BAT may be a valuable target for the prevention of obesity. In addition, WAT adipocytes exhibit a BAT phenotype when subjected to certain stimuli, a process called browning [16; 17]. The prerequisite for browning is that the free fatty acids (FFAs) released during lipolysis are absorbed by cells that require energy; carnitine palmitosyltransferase 1 (CPT1) can transport FFAs to the mitochondrion, which is the site for fatty acid \(\beta\)-oxidation (FAO) to produce acetyl coenzyme a. FAO is necessary for the browning process induced by UCP1 [18; 19]. _Ecklonia stolonifera_ is an edible brown alga widely distributed in Korea and Japan. It belongs to the kelp family and is rich in many polyphenol compounds, mainly tannins [20]. Dieckol is a primary tannm compound found only in brown algae and is an indicator component of _E. stolonifera_ extract (ESE). Recent studies have shown that ESE exhibits anti-obesity, antioxidant, anti-inflammatory, and antidiabetic activities [21; 22]. Previous studies have also reported that ESE can inhibit fat accumulation by increasing lipolysis and WAT browning [23; 24]. Therefore, in this study, a clinical trial test material (SEETM, test material of _E. stolonifera_ extract) was prepared to develop a healthy functional food based on the anti-obesity effect of ESE.