Nature India | Indigenus

Big fat studies

As Body Volume Index (BVI) takes the place of dear old Body Mass Index (BMI) to become the new accepted measure of general adiposity and obesity, textbooks will hopefully be re-written and fitness experts sensitised to the ‘gold standard’.

It appears more scientific to be able to determine the difference between muscle and fat in the body to assess how obese or not a person is. This is what BVI does as opposed to BMI, which is a measure of body weight based on a person’s weight and height. BVI also takes into account body shape determining exactly where weight is distributed across the body.

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Parallely, two interesting studies in Nature Genetics this week look at new genomic regions associated with and sex-specific differences occuring in obesity. The first — a meta-analysis of 46 genome-wide association studies for BMI — identified 18 genomic regions newly associated with BMI, and confirmed 14 previously associated regions. This study highlights the role for neuronal regulators of energy balance in weight regulation.

The second — a meta-analysis of 32 genome-wide association studies for waist-hip ratio (WHR) — a measure of body fat distribution — identified 13 genomic regions newly associated with WHR. Seven of these associations show a stronger effect in women, highlighting sex specific differences.

A whole set of new genes associated with body fat distribution and obesity have been identified in these studies and that includes the largest study yet of DNA variation across our genomes involving almost ¼ million people.

Variations in DNA sequence in these genetic regions can actually be linked to whether we are apple-shaped or pear-shaped, the researchers say. A good lot of these variations have a markedly stronger effect in women than in men.

Another noteworthy aspect of these findings is that many genetic regions for WHR have been found to be independent of BMI. Genetics seems to be pointing us to biological distinctions between two components of the regulation of weight – how much we eat, and how and where calories are stored as fat.

Such fat news for a week that will see a lot of happy eating and bingeing in India, what with the festival season right ahead! Not everything can be dictated by your genes, shall we say?

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