Fatty acids (FAs), as primary constituents of triglycerides, are of three distinct types: saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs). PUFAs, which are derived from diverse biological pathways, are of particular significance owing to their multifaceted roles and potential therapeutic implications. Moreover, high amounts of fat can lead to lipotoxicity, which is associated with immunometabolic pathways and cancer. Lipids, such as cholesterol and triglycerides, possess a hydrophobic nature, necessitating their transport into the bloodstream through association with proteins, notably lipoproteins. Dietary recommendations advocate the incorporation of fats, emphasizing that 30% of daily caloric intake should be derived from this macronutrient. In intensive care medicine, dyslipidemia is commonly observed. Acute critical illnesses disrupt lipid metabolism, resulting in alterations in lipid components and metabolic pathways, thereby influencing patient outcomes during the inflammatory response. Parenteral and enteral nutrition solutions containing fats play vital roles in intensive care unit (ICU) therapy, although debate persists regarding the ideal FA composition. While fat-modified enteral solutions hold promise for enhancing feeding tolerance and mitigating complications, uncertainties surround the effects of omega-3 FAs on inflammation and mortality. Fat overload syndrome, resulting from rapid infusion of intravenous fat emulsions, can lead to multiorgan failure, affecting the cardiovascular, respiratory, renal, neurological, and hemato-immunological systems. Elevated triglyceride levels and fat droplets typically resolve upon cessation of infusion, highlighting the importance of monitoring infusion rates to prevent this syndrome. Carnitine deficiency, which is essential for FA transport across mitochondria, is prevalent among critically ill patients and may manifest as unexplained hypertriglyceridemia, fatty liver, or severe cardiomyopathy. Supplementation with carnitine has shown promise in reducing inflammatory biomarker levels and mortality rates in ICU patients. Omega-3 FAs, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), demonstrate potential benefits in conditions such as ARDS, neuroprotection following traumatic brain injury, and possibly mitigate delirium episodes in ICU patients. Although high-quality randomized control trial and meta-analyses should be viewed as hypothesis-generating, ASPEN and ESPEN guidelines highlight the potential benefits of fish oil-containing parenteral solutions reducing infection risk and length of hospital stay, even though the Surviving Sepsis Campaign does not specifically recommend lipid-adapted therapy. These findings emphasize the critical role of lipid management in improving the outcomes of critically ill patients.