**Abstract**

Obesity is strongly associated with the insulin resistance development and is an integral pathogenic part of the metabolic syndrome, type 2 diabetes, atherosclerosis, and other comorbid pathologies. It is well known that the obesity causes the disorders in adipose tissue endocrine and metabolic activity, which results in the activation of free radical processes. The administration of natural origin substances with antioxidant properties could be a promising direction for obesity and overweight correction. The objective of the current study was to evaluate the usefulness of natural origin active substances with antioxidant properties' administration under the obesity and comorbid disorder treatment. This chapter presents the results of experimental studies that proved the usefulness of phenolic compounds from apple food concentrate (*Malus domestica* L.) and dry bilberry extract (*Vaccinium myrtillus* L.) application under experimental metabolic syndrome, insulin resistance syndrome, and type 2 diabetes mellitus, which are extremely associated with obesity. It has been found that due to expressive antioxidant activity, these compounds exhibit the high efficiency in carbohydrate metabolism disorders' correction (in cases of metabolic syndrome and type 2 diabetes), lipids metabolism disorders' correction (in case of metabolic syndrome), preventing of endothelial dysfunction under experimental insulin resistance, and normalization of antioxidant status in the liver (under experimental type 2 diabetes mellitus).

**Keywords:** obesity, apple polyphenol extract, blueberry dry extract, metabolic syndrome, insulin resistance, antioxidant activity, diabetes mellitus
