A true obesity epidemic is gradually
advancing throughout the developed world. A large new Danish-British study from
the University of Copenhagen and University of Bristol documents for the first
time a definite correlation between a high BMI and the risk of developing
life-threatening cardiac disease.
Heart
attack, atherosclerosis of
the coronary arteries and angina –
also called ischemic heart
disease – are the most common causes of death in adults worldwide. In
the US alone, 500,000 people die each year from heart disease. Now for the
first time, researchers can show that there is a direct correlation between a
high Body Mass Index (BMI) and the risk of developing heart disease.
The new
study is published in the esteemed journal PLoS Medicine on
May 1. Here scientists from the University of Copenhagen and their colleagues
at the University of Bristol show that obesity in itself is
damaging to heart health. The results are based on a study of 75,627
individuals.
"Our
study supports existing observational studies, but weighs much heavier as a
scientific argument. A BMI increase of 4 kg/m2 increases the risk of heart
disease by no less than 52 per cent," says Professor Børge Nordestgaard,
chief physician at Copenhagen University Hospital and clinical professor at The
Faculty of Health and Medical Sciences, University of Copenhagen.
Obesity
a problem in itself
"By
doing epidemiological studies combined with genetic analysis, we have been able
to show in a group of nearly 76,000 persons that a high BMI is enough in itself
to damage the heart. Observational studies have also suggested a relationship
between heart disease and obesity, but that is not enough to prove a direct
correlation. Obese people can share characteristics or lifestyle traits that
have an influence on both the heart and weight. Or there can be a reverse
causality – that is, it is the diseased heart that causes obesity and not the
other way round," explains Professor Børge Nordestgaard.
No
shortcuts in sight
Scientists
analysed data from two large population studies – the Copenhagen General
Population Study and the Copenhagen City Heart Study – involving about 76,000
adult individuals who were given a physical examination and were asked
questions about their lifestyle. The researchers found that individuals with a
high BMI had a 26 per cent greater risk of contracting heart disease. By combining
data with analyses of the patients' genotypes, researchers saw an increased
risk of up to 52 per cent.
Three
ordinary genetic variations were used in the study – all associated with a high
BMI. Because genes are inherited at random and are free from reverse causality,
the analysis allowed researchers to demonstrate a convincing causal correlation
between high BMI and heart disease.
According
to professor Børge Nordestgaard, there are only two ways out of the obesity epidemic,
which he considers to be a major problem for Western civilization. Although
fewer people smoke and more eat a healthy diet – far too many people eat too
much:
"It
is really very simple. If you want to lose weight, you have two options. You
can exercise or you can eat less. There are no shortcuts, it is either or – and
preferably both," says Nordestgaard.
Dr
Nicholas Timpson, Lecturer in Genetic Epidemiology from University of Bristol's
School of Social and Community Medicine, adds: "In light of rising obesity
levels, these findings are fundamental to improving public health.
Our
research shows that shifting to a lifestyle that promotes a lower BMI (even if
it does nothing else) will reduce the odds of developing the disease." Dr.
Timpson is the lead author from the Bristol team.
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