BACKGROUND: For cachectic patients with chronic respiratory disease (CRD), conventional enteral nutrition formula is an optional treatment to maintain energy balance. The molecular mechanisms by which enteral nutrition formula controls appetite and weight remain unknown. We examined whether enteral nutrition formula rich in octanoic acids would increase plasma levels of ghrelin, an appetite-stimulating hormone produced in the stomach, in cachectic patients with CRD. METHODS: Plasma ghrelin profiles in cachectic patients with CRD were assessed and compared with those in age- and sex-matched controls. Plasma levels of acyl-ghrelin, an active ghrelin modified by octanoic acids, and desacyl-ghrelin were measured separately. We examined changes in 24-h plasma ghrelin profiles before and after single administration of the formula. We also evaluated the effects of 2-week administration of the formula on plasma ghrelin levels and nutritional status in patients. RESULTS: The ratio of acyl-ghrelin to desacyl-ghrelin in plasma was lower in patients than in controls. Single administration of the formula did not change plasma desacyl-ghrelin levels, but induced an increase in acyl-ghrelin levels. Two-week treatment with the formula was effective in increasing weight and acyl-ghrelin, along with improving nutritional status in patients. CONCLUSION: These results show that the formula contributes to increased weight, which may be associated with induction of acyl-ghrelin production in cachectic patients with CRD.