Changes in fat-free mass during significant weight loss: a systematic review.

Author: Chaston TB, Dixon JB, O'brien PE

Author affiliation: 1Australian Centre for Obesity Research and Education, Monash University, Monash Medical School, The Alfred Hospital, Melbourne, Victoria, Australia.

Publication date & source: 2006.10.31, Int J Obes (Lond)., [Epub ahead of print]

Objective:To identify the proportion of weight lost as fat-free mass (FFM) by various weight loss interventions.Methods:Medline and Embase were systematically searched for reliable measurements of FFM before and after weight loss of >10 kg and eligible data were pooled. In a fixed effect model of % FFM loss/weight loss (%FFML), linear regression analysis was used to determine the influence of degree of caloric restriction, exercise, magnitude of weight loss, initial body mass index (BMI) and type of surgery.Results:Data were included from 26 cohorts treated with dietary and behavioral interventions and 29 cohorts of bariatric surgery patients. The degree of caloric restriction was positively associated with %FFML (r (2)=0.31, P=0.006) and in three randomized controlled trials exercise was shown to decrease %FFML. Compared with laparoscopic adjustable gastric banding (LAGB), biliopancreatic diversion (BPD) and roux en Y gastric bypass (RYGB) caused greater log(e) (natural log) %FFML (r (2)=0.453, P<0.001). Differences in log(e) %FFML between surgical procedures were independent of initial BMI and magnitude of weight loss.Conclusions:The degree of caloric restriction, exercise and rate of weight loss influence the proportion of weight lost as FFM after non-surgical interventions. For surgical interventions, BPD and RYGB result in greater %FFML than LAGB.International Journal of Obesity advance online publication, 31 October 2006; doi:10.1038/sj.ijo.0803483.