Disease causes of poor appetite. Chronic conditions can cause poor appetite including: Cancers (ovarian, pancreatic, colon, or stomach, for example). Chronic obstructive pulmonary disease (COPD, includes emphysema and chronic bronchitis).n some cases, poor appetite may be a symptom of a serious or life-threatening condition that should be immediately evaluated in an emergency setting. These include: Dehydration (loss of body fluids and electrolytes, which can be life threatening when severe and untreated).