another body fat study

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This was a limited 5.8 year study for people between the ages of

50-64. Same conclusions, though. High body fat is bad, and so is low

fat-free mass.

Mortality and body fat and fat-free mass

Nutrition Research Newsletter, Sept, 2004

The health effects of obesity have been thoroughly studied using BMI

as a measure of adiposity and all-cause mortality as the endpoint.

Many studies have identified U- or J-shaped associations between BMI

and mortality. It has been hypothesized that all-cause mortality is

increased at high levels of body fat mass and at low levels of

fat-free mass (FFM), creating this U-shaped association. Previous

research has investigated this using total body potassium counting or

measurements of skinfold thickness to determine lean and fat mass.

However, a new prospective study measured body composition by

bioelectrical impedance to investigate whether the association between

BMI and all-cause mortality could be disentangled into opposite effect

of body fat and FFM.

Data was used from 27,178 men and 29,875 women included in the Danish

follow-up study, Diet, Cancer and Health. The subjects were 50 to 64

years old. All anthropometric data were collected at two study clinics

in Aarhus and Copenhagen. Body composition was assessed by

bioelectrical impedance. All-cause mortality was the endpoint in the

study with the median follow-up period being 5.8 yr.

Men and women showed similar J-shaped associations between body fat

mass index and mortality after adjusting for FFM and smoking. The

mortality rate ratios in the upper part of body fat mass were 1.12 per

kg/[m.sup.2] in men and 1.06 per kg/[m.sup.2] in women. Reversed

J-shaped associations were found between FFM index and mortality with

a tendency to level off for high values of FFM. There were no effect

modifications of age, time since baseline examination, smoking or

hospital contacts.

The results demonstrated that the U-shaped association between BMI and

all-cause mortality reflects the combination of a J-shaped association

between body fat mass index (BFMI) and mortality and a reverse

J-shaped association between FFM index (FFMI) and mortality. Both high

body fat and low FFM are independent predictors of all-cause

mortality. However, caution should be taken when generalizing these

findings since the age range was limited to 50 to 64 years old and

there was a relatively short follow-up period.

Janne Bigaard, Kirsten Frederiksen, Anne Tjonneland, et al., Body fat

and fat-free mass and all-cause mortality, Obesity Research 12(7):

1042-1054 (July 2004) [Address correspondence to Janne Bigaard,

Institute of Cancer Epidemiology, The Danish Cancer Center,

Strandboulevarden 49, DK-2100 Copenhagen, Denmark. E-mail:

janne@...]