A standard enteral formula versus an iso-caloric lower carbohydrate/high fat enteral formula in the hospital management of adolescent and young adults admitted with anorexia nervosa: a randomised controlled trial

Background: The nutritional rehabilitation of malnourished patients hospitalised with anorexia nervosa is essential. The provision of adequate nutrition must occur, while simultaneously, minimising the risk of refeeding complications, such as electrolyte, metabolic, and organ dysfunction. The aim of this study was to compare the efficacy and safety of an iso-caloric lower carbohydrate/high fat enteral formula (28% carbohydrate, 56% fat) against a standard enteral formula (54% carbohydrate, 29% fat). Methods: Patients (aged 15–25 years) hospitalised with anorexia nervosa were recruited into this double blinded randomised controlled trial. An interim analysis was completed at midpoint, when 24 participants, mean age 17.5 years (± 1.1), had been randomly allocated to lower carbohydrate/high fat (n = 14) or standard (n = 10) feeds. Results: At baseline, there was no significant difference in degree of malnutrition, medical instability, history of purging or serum phosphate levels between the two treatment arms. A significantly lower rate of hypophosphatemia developed in patients who received the lower carbohydrate/high fat formula compared to standard formula (5/14 vs 9/10, p = 0.013). The serum phosphate level decreased in both feeds, however it decreased to a larger extent in the standard feed compared to the lower carbohydrate/high fat feed (standard feed 1.11 ± 0.13 mmol/L at baseline vs 0.88 ± 0.12 mmol/L at week 1; lower carbohydrate/high fat feed 1.18 ± 0.19 mmol/L at baseline vs 1.06 ± 0.15 mmol/L at week 1). Overall, serum phosphate levels were significantly higher in the lower carbohydrate/high fat feed compared with standard feed treatment arm at Week 1 (1.06 ± 0.15 mmol/L vs 0.88 ± 0.12 mmol/L, p < 0.001). There was no significant difference in weight gain, number of days to reach medical stability, incidence of hypoglycaemia, or hospital length of stay. Conclusions: The results of this study indicate that enteral nutrition provided to hospitalised malnourished young people with anorexia nervosa using a lower carbohydrate/high fat formula (28% carbohydrate, 56% fat) seems to provide protection from hypophosphatemia in the first week compared to when using a standard enteral formula. Further research may be required to confirm this finding in other malnourished populations. Trial Registration: ANZCTR, ACTRN12617000342314. Registered 3 March 2017, http://anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=12617000342314