Ultra-processed foods (UPFs) and their nutritional value have become a trending topic in the scientific community because of their increasing demand, and their potentially adverse effects on human health. Besides the poor nutritional value attributed to UPFs, countless studies have also reported the presence of different dietary oxidized substances in these meals. DOxS are associated with several chronic diseases such as cardiometabolic diseases (CMD), cancer, diabetes, Parkinson’s, and Alzheimer’s disease. In this study, a database of DOxS and other dietary metabolites detected in 63 UPFs meals part of the Western diet is reported. Significant differences were found in DOxS and phytosterol contents between ready-to-eat and fast food (FF). Putative biomarkers were suggested for RTE (brassicasterol) and FF (7α-OH and 7β-OH), as well as for all 6 different food categories: dairy (brassicasterol), eggs & derivatives (stigmasterol and β-sitosterol), meat & poultry (7α-OH), seafood, baby food (β-sitosterol), and others (campesterol). Ideally, the use of dietary biomarkers could potentially help in the future to identify in an early stage the presence of different chronic diseases, and even, prevent their development. Nevertheless, an exposure assessment is critical to understand the exposure level of DOxS and their relationship with different chronic diseases.