The Global Burden of Disease report – a massive research effort involving almost 500 scientists in 50 countries – also concludes that we have finally got a handle on some common infectious diseases, helping to save millions of children from early deaths. But collectively we are spending more of our lives living in poor health and with disability.
"The Global Burden of Disease 2010 is the most comprehensive assessment of human health in the history of medicine," says Richard Horton, editor of The Lancet, in which the report will be published. "It provides insights into human health that are comparable in scope and depth to the sequencing of the human genome."
The report assessed the prevalence of diseases and causes of death across the globe in 2010, and compared these to data collected in 1990 to identify any trends.
For the first time on a global scale, being overweight has become more of a health problem than lack of nutrition. In 1990, undernutrition was the leading cause of disease burden, measured as the number of years of healthy life an average person could expect to lose as a result of illness or early death. Back then, a high body-mass index, or BMI, was ranked tenth. Now, undernutrition has dropped to eighth place, while BMI has risen to become the sixth leading cause of disease burden.
Too much to eat
"A greater amount of disease burden has occurred because people are fat and have too much to eat, as opposed to having too little to eat," says Alan Lopez at the University of Queensland in Brisbane, Australia, who worked on the study.
Being overweight can hike a person's blood pressure and cause stroke and heart disease; together, these two conditions are responsible for a quarter of all deaths. And the problem isn't limited to the west – the Middle East is one region that is seeing significant increases in BMI.
But while more of us may be overweight, we are also living longer. In some countries, the change has been huge – the Maldives, for example, has seen an increase in life expectancy of almost 30 years since the 1970s. Rural health programmes have also contributed to big improvements in countries including Bangladesh and Iran.
"There has been a lot of progress," says Majid Ezzati at Imperial College London, who led part of the study investigating the risk factors of disease. "These are countries that have implemented programmes in large regions and nationwide to get interventions to the people that really need them."
Progress in eliminating the causes of early childhood death – mainly infections, diarrhoea and birth problems – has been astounding. The rate of death in the under-5s has dropped by 60 per cent since 1990.
High mortality
Sub-Saharan Africa is still experiencing high levels of mortality from infectious diseases such as HIV and malaria, yet globally deaths from infectious diseases have dropped. In fact, we are more likely to die from non-infectious diseases – especially those caused by being overweight.
Looking forward, obesity and the use of tobacco and alcohol are obvious targets for health policy change. But it is also important to focus on healthy ageing.
"The large burden [of disease] related to disability was a surprise," says Christopher Murray at the University of Washington in Seattle. "There's been a focus on mortality, but there's a huge volume [of disease burden] related to things that don't really kill you."
Musculoskeletal disorders – such as neck and back pain – dominate this category, as do mental disorders and substance abuse.
There's a need to improve awareness of these chronic conditions in the developing world, says Irene Agyepong at the University of Ghana in Accra, who was not involved in the study. "The kind of awareness we have in the western world is not there in the south," she says. "We have to focus on it now rather than wait until it is upon us, like the HIV AIDS epidemic is on us."
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