Weight Loss and Body Composition

August 8, 2006

Hi JW:

Here is one study about changes in body composition during weight

loss in obese subjects. Granted the food restriction was imposed in

this study by bariatric surgery, which conceivably might have

different effects from simple restriction:

" Obes Surg. 2006 Apr;16(4):469-77.

Body composition and metabolic changes following bariatric surgery:

effects on fat mass, lean mass and basal metabolic rate.

Carey DG, Pliego GJ, RL, Skau KB.

Health and Human Performance, Mail #5003, University of St. ,

2115 Summit Avenue, St. , MN 55105, USA.

BACKGROUND: Bariatric surgery has become the method of choice for

weight loss in severely obese patients. While the incidence of

obesity and its co-morbidities have been well-documented, less is

known about the outcomes of the surgery as it relates to body

composition and metabolic changes. METHODS: 19 bariatric surgery

patients (14 female, 5 male) were assessed for basal metabolic rate

(BMR), percent fat, fat mass, and lean body mass (LBM) just prior to

surgery and at 1, 3 and 6 months after surgery. RESULTS: Analysis of

Variance (ANOVA) using the general linear model indicated significant

changes in all measures of body composition for each time period.

Linear regression was developed for each of these measures. Of the

39.7-kg weight loss, 26.4 kg (66.5%) was fat mass loss and 13.3 kg

(33.5%) was LBM loss. BMR significantly decreased from pre-surgery

(2091 kcals) to 1 month post-surgery (1758 kcals), with no

significant changes in subsequent time periods. Repeated measures

ANOVA for the ratio of BMR/LBM indicated no significant differences

for any comparison of time periods (F=2.29, P=.111), suggesting that

there is no adaptation of an energy-conserving mechanism in these

patients. CONCLUSION: Bariatric surgery was highly successful in

inducing significant changes in body weight (39.7 kg), fat mass (26.4

kg), % body fat (7.9%) but also lean body mass (13.3 kg). The 440

kcal decrease in BMR, while significant, was not greater than

expected due to significant decreases in LBM.

PMID: 16608613 "

You will note that, once again, in these obese subjects, between 60%

and 70% of the weight lost was fat mass.

Rodney.

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