INTRODUCTION Type 2 diabetes mellitus (T2DM) is recognized as a major public health problem in the modern world, with its prevalence increasing each year. Consistently poor lifestyle habits — namely, nutritional excess coupled with sedentary behavior — are the leading causes of obesity, which in turn leverages the gradual desensitization of cells to insulin, followed by the onset of insulin resistance (IR) and the subsequent development of T2DM. Countless studies and ongoing research have confirmed that nutrition plays a definitive role in contributing to the development and onset of T2DM. However, in recent years, there has been increasing controversy surrounding the role that branched-chain amino acids (BCAAs) may play in influencing IR and the development of T2DM.

AIM To review existing literature regarding both the purportedly harmful and beneficial roles and impacts of BCAAs on metabolic health, in order to better understand the contradictory nature of BCAAs and their effects on IR and T2DM.

METHODS Relevant research, review articles and epidemiological studies spanning the time frame from 2004 to 2020 were collected, analyzed and summarized with the goal of underscoring and delineating the conflicting roles of BCAAs.

RESULTS Evidence of beneficial effects of BCAAs includes enhanced muscle protein synthesis, more efficient glucose homeostasis, increased satiety, better body composition and improved body weight regulation. Evidence of harmful effects of BCAAs includes elevated fasting concentrations of circulating BCAAs correlating with an increased risk of IR and T2DM in human and rodent models.

DISCUSSION In spite of the various studies that have been undertaken to shed further light on BCAAs, it still remains unclear whether they are simply markers of metabolic disturbances that ultimately lead to the development of T2DM, or if they are, at least in part, the actual cause of metabolic disturbances leading to T2DM. The general consensus amongst the scientific community is that more research is needed on this topic.