Adolescents hospitalized for anorexia nervosa could benefit from a more-aggressive feeding strategy – one that contradicts the current "start low, go slow" approach to providing calories, according to a new study.

Administration of more than the conservative 1,200 calories/day initially could prevent weight loss that typically is seen in the first week in the hospital and could mean many patients will leave the hospital sooner, Andrea K. Garber, Ph.D., lead author of the study, said in an interview.

"It was really a known thing in clinical practice – that patients on this ‘start low and go slow’ approach would lose weight initially. It was just accepted as part of the course of recovery," said Dr. Garber, who is on the pediatrics faculty within the division of adolescent medicine at the University of California, San Francisco.

Fluids shifts are widely believed to cause this initial weight loss. "Our data support that it was related in part to fluid shifts. We also really believe, and were able to show, that it is due to underfeeding as well," Dr. Garber said. "That was a surprise."

Dr. Garber and her associates in the UCSF Pediatric Clinical Research Center studied 35 patients hospitalized for weight loss secondary to anorexia nervosa (J. Adolesc. Health 2011 [doi:10.1016/j.jadohealth.2011.06.011]).All except one of the participants were girls; the mean age was 16 years. The mean body mass index on admission was 16 kg/m² (range, 11-22 kg/m²).

Although a range of calories initially were prescribed, from 800-2,200 calories/day, 94% started on 1,400 calories or fewer per day. This approach approximated the current 1,200-calorie/day recommendations from the American Psychiatric Association (Am. J. Psychiatry 2006;163:4-54) and the American Dietetic Association (J. Am. Diet. Assoc. 2006;106:2073-82).

"A major finding of ours is that the recommendations in place are probably not working," Dr. Garber said.

Most participants, 29 of the 35 treated according to the more-conservative protocol, initially lost weight. Significant weight gain was not observed until day 8 of admission. A higher-calorie starting diet predicted an increase in percentage median BMI (50th percentile adjusted for age and gender) and shorter length of stay. For every 100-calorie increase at baseline, the rate of percentage median BMI increased by 0.02%, and length of time in the hospital decreased by a mean 0.9 days.

"It’s an interesting study because it challenges the current practices," said Dr. Michelle Marks, director of pediatric hospitalist medicine, Cleveland Clinic, said in an interview when asked to comment.

Since 2005, Cleveland Clinic protocol has been to start most patients at 1,200 calories and increase intake by 250 calories/day, based on weight gain. "I have often thought that it would be realistic to start most of these kids at a higher initial calorie [baseline]," Dr. Marks said.

Dr. Marks urged some caution as well. "Even though we may believe that we may use more calories at the beginning, it’s not clear at what level to start. So this paper shouldn’t have people saying ‘Oh, great. I can start at any calorie I want, and if I start at 2,000 calories, it’s okay.’ " She added that patients with lower initial body weights should be watched more closely.