Changes in fat-free mass during significant weight loss: a systematic review.
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.
Chaston
T B
TB
Australian Centre for Obesity Research and Education, Monash University, Monash Medical School, The Alfred Hospital, Melbourne, Victoria, Australia.
Dixon
J B
JB
O'Brien
P E
PE
D015502:Absorptiometry, Photon; D001823:Body Composition / Q000502:physiology*; D004038:Diet, Reducing; D015444:Exercise; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D009765:Obesity / Q000178:diet therapy / Q000601:surgery / Q000628:therapy; D016032:Randomized Controlled Trials as Topic; D015431:Weight Loss / Q000502:physiology*