Decreased appetite in adults can result from various physical and psychological factors. Common causes include infections, chronic diseases such as diabetes or cancer, gastrointestinal disorders, hormonal imbalances, and medication side effects, including antibiotics like cephalexin capsules. Mental health conditions such as depression, anxiety, and stress often reduce interest in food. Aging may also diminish taste and smell, lowering appetite. Lifestyle habits like irregular eating patterns, excessive alcohol consumption, or lack of physical activity contribute as well. Identifying the underlying cause is essential, as persistent appetite loss can lead to nutrient deficiencies, weight loss, weakened immunity, and overall health decline significantly.