Introduction: The rising prevalence of obesity has led to growing interest in very low-calorie diets (VLCDs), which typically provide fewer than 800 kcal/day and limit carbohydrate intake to 20-50 g/day. These diets are promoted for their rapid weight loss effects; however, concerns have emerged regarding their long-term safety and physiological impact [1–3].

Methodology: A comprehensive review was conducted to assess the physiological and psychological effects of prolonged VLCD adherence. Studies published between 2009 and 2025 were retrieved from PubMed, ScienceDirect, and Google Scholar. Selection criteria focused on research examining outcomes related to bone health, lean body mass, liver function, cardiometabolic risk, and mental health.

Results: A total of 31 studies were included, with 14 addressing multiple complications. VLCDs were associated with reduced bone mineral density and quality, increasing the risk of osteoporosis [4]. Lean body mass loss, especially in older adults, was commonly reported and linked to sarcopenia, decreased physical function, and frailty [2]. Hepatic issues such as portal inflammation and fibrosis were observed, particularly with rapid weight loss [5]. Weight cycling, characterized by repeated loss and regain, was associated with insulin resistance, dyslipidemia, hypertension, and increased cardiometabolic risk [6]. In mental health, while short-term mood improvements may occur with behavioral support, long-term VLCD use has been linked to adverse effects on cognitive function, mood, and anxiety [3].

Conclusion: Although VLCDs can induce short-term weight loss, prolonged use raises significant safety concerns. This review highlights potential risks affecting skeletal, muscular, hepatic, metabolic, and psychological health. These findings support the need for individualized dietary planning, incorporation of physical activity, and professional supervision to ensure nutritional adequacy and minimize health risks.