Obesity is a common nutritional disorder associated with a variety of chronic diseases, among them, type 2 diabetes (T2DM) has emerged as a serious worldwide health problem. Insulin resistance and β cell dysfunction are the main pathological characteristics of T2DM, and obesity and hyperlipidemia are the critical causal factors. It is commonly accepted that dietary factors are of paramount importance in the management of obesity and T2DM. Particularly, many botanic products and their extracts are endowed with a wide spectrum of biological activities, making them extensively reviewed as anti-obesity and anti-diabetes dietary supplements or new drug candidates. In this review, we aimed to summarize the effects, related mechanisms, and safety issues of dietary continents on obesity and T2DM, to provide theoretical support for better research and development of dietary therapy strategy for the treatment of obesity and T2DM. Based on many clinical investigations, specific carbohydrates and fatty acids, such as dietary fibers, polysaccharides, unsaturated fatty acids, have hypoglycemic and hypolipidemic effects. Vitamin D plays an important role in metabolism and immunity modulation. Apart from them, natural bioactive ingredients from plants, such as flavonoids, polyphenols, alkaloids, terpenoids, polysaccharides, and quinones are efficient in helping weight loss and improving insulin sensitivity and glycemic control. They can protect β cell function by antiinflammation, anti-oxidation, and anti-apoptosis properties, as well as regulating lipid metabolism. Therefore, promoting the consumption of diverse natural bioactive ingredients-rich products could be an effective nutritional strategy to benefit patients with obesity and type 2 diabetes.