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Science & Technology

Obese exposure

Aug 15, 1995 | From the print edition
Detecting the body's fat deposits

The effects of body fat are no (Credit: Arvind Yadav /CSE)SLIM figures are in vogue. Flab is consid-
ered ugly aesthetically and unhealthy
scientifically. Recently, researchers at
the London-based Hammersmith
Hospital developed a state-of-the-art
technique for mapping fat deposits in
the body through Magnetic Resonance
Imaging (MRI) that leaves no place for
fat to hide (New Scientist, Vol 146, No 1974).

Weight watchers usually gauge body
fat by crude methods like measuring
skin fold thickness and ratios of height
to weight and of waist to hip. Though
these reveal the total amount of flab in
the body, nothing is specified about its
distribution, especially its deposition
around the internal organs, which is
crucial to illness related to obesity such
as coronary heart disease.

With an MRI scan, 3-dimensional
images of slices of body are got by pushing the subject slowly through a magnetic field, pausing at regular intervals
of 3 centimetres to pick out fat contours. Then, the composition of a slice
of flesh up to 10 millimetres thick is
analysed by using brain-imaging
software that processes the slices to
reveal dazzling white layers of fat on a
computer screen.

The technique has confirmed the
notion that people with fat concentrated
around their stomachs are more prone
to heart attacks than people with heavy
bottoms. According to Jimmy Bell of the
Hammersmith Hospital, obese people
have most of their fat deposited around
the internal organs. That fat people have
about 2.7 times as much fat as thin people but 4 times as much visceral fat, has
been established.

The effect of weight loss on obese
people has also been revealed. Previous
findings that weight loss caused a
change in fat distribution with internal
deposits shrinking most sharply, has
been backed by this technique. Further,
the role of fat in the development of our
bodies and brains has been invekigated.

A preliminary study has revealed
that the composition of adipose tissue in
infants alters with age. With unsaturated fats gradually forming the bulk of the
fat deposits, the saturated fat content
goes down. The reason put forth is that
saturated fats being high in energy content, meet the energy requirements of a
growing brain. However, Louise Thomas of the Hammersmith team says that
the amount of polyunsaturates peaks at
about 10 months of a baby's age, before
plummeting to adult levels.

But the mRi technique has its limitations. Besides being expensive, it is
insensitive to individual fatty acids in
the body. However, slicing through fat
by scanners is truly revolutionising the
study of the effect of body fat on general body health.


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