- Fat loss extends human longevity.
- Weight loss may extend longevity only if sufficient loss
is from fat loss.
- Weight loss that is related to increases in mortality may
be a result of lean body mass
Obesity is associated with increased all-cause mortality.
Moreover, modest reductions in obesity are associated with
reduced obesity-related comorbidities. This has lead
to the speculation that weight loss itself might strongly
be associated with reduced all-cause mortality rate. However,
there has been counter-intuitive evidence that the weight
loss is associated with increased mortality. This issue
remains controversial. To see how weight loss operates
in mortality analyses, we tried to separate the effects of weight
loss (WL) from those of fat loss (FL). Specifically,
WL and FL were hypothesized to have increasing and decreasing
effects, respectively, on all-cause mortality rate.
Using Data from the Tecumseh Heart Study (THS;n-1890) and
the Framingham Heart Study (FHS;n-2734) we investigated how
WL and FL are associated with all-cause mortality.
Materials & Methods:
For both studies, fatness was measured by skin fold thickness
and the losses in kg (WL and FL) were calculated as the measurements
taken at time 1 minus those at time 2, this being later than
time 1 and earlier than end of the follow-up.
Results from logistic regression analyses in both data bases,
adjusted for age, sex, and smoking status, supported the
hypotheses. That is, WL and FL were positively and
negatively associated with all-cause mortality, respectively
(OR for one unit change in WL=1.02 (p<0.001) for FHS and
1.06 (p=0.002) for THS; OR for one unit change in FL=0.97
(p=0.049) for FHS 0.83 (p=0.022) for THS). Therefore, the
positive association of weight loss with mortality might
have resulted from lean body mass loss. In addition,
these results underscore the importance of more accurate
and precise body composition measurements for better understanding
of measurements for better understanding of mechanisms of
their effects on all-cause mortality. To our knowledge,
this is the first study to show that fat loss extends longevity
among humans. These results suggest that weight loss
may only extend longevity if a sufficient proportion of the
weight loss is lost as fat.
*Reprinted from Tanita Corporation
of America, Inc.
Sources: Angelo Pietrobelli, Myles S. Faith, Moonseong Heo, Steven
B. Heymsfeld, David B. Allison,
Obesity Research Center, St. Luke's-Roosevelt Hospital Center,
Columbia University College of Physicians & Surgeons, New York, NY USA
First printed in the International Journal of Obesity and related metabolic
Volume 22, Supplement 3, Aug. 1998.
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