Anxiety Disorder: Loss of appetite is a common symptom of anxiety disorders, such as generalized anxiety disorder or panic disorder. The presence of anxiety symptoms, such as worry, fear, or nervousness, supports this diagnosis.
Depression: Depression is another common cause of loss of appetite, and it can be difficult to distinguish from anxiety. However, depressive symptoms, such as sadness, hopelessness, or loss of interest in activities, are typically more prominent.

Gastrointestinal Disorders: Conditions like gastroesophageal reflux disease (GERD), irritable bowel syndrome (IBS), or inflammatory bowel disease (IBD) can cause loss of appetite due to symptoms like nausea, vomiting, or abdominal pain.
Medication Side Effects: Certain medications, such as antidepressants, antihistamines, or chemotherapy, can cause loss of appetite as a side effect.
Sleep Disorders: Sleep apnea, insomnia, or restless leg syndrome can lead to loss of appetite due to fatigue, stress, or disrupted sleep patterns.

Cancer: Although less common, cancer can cause loss of appetite, especially in advanced stages. It is essential to rule out cancer, particularly if there are other symptoms like weight loss, fatigue, or pain.
Neurological Disorders: Conditions like Parkinson's disease, multiple sclerosis, or dementia can cause loss of appetite due to neurological dysfunction.
Infections: Chronic infections like tuberculosis, HIV, or hepatitis can lead to loss of appetite, especially if left untreated.

Endocrine Disorders: Rare endocrine conditions like adrenal insufficiency, hypopituitarism, or pheochromocytoma can cause loss of appetite.
Nutritional Deficiencies: Deficiencies in vitamins like B12 or minerals like zinc can lead to loss of appetite, although this is relatively rare.
Psychiatric Conditions: Conditions like anorexia nervosa, bulimia nervosa, or avoidant/restrictive food intake disorder can cause loss of appetite, although these typically involve significant weight loss or distorted body image.