Weight loss can be the first manifestation of some infectious diseases, such as HIV infection, tuberculosis, endocarditis, and fungal and parasitic infections. Hyperthyroidism or pheochromocytoma increase basal metabolism; the elderly with apathetic hyperthyroidism may present with weight loss and weakness, with few other manifestations of thyrotoxicosis. New-onset diabetes mellitus is often accompanied by weight loss due to glycosuria and loss of the anabolic effects of insulin. Nutravesta Proven Reviews