The global obesity epidemic is grabbing the headlines and spurring policy changes – and in the process, the undernourished are being increasingly forgotten.
That is the conclusion of a study showing that, as the economies of developing countries grow, the overweight and obese are gaining weight quickly, but the underweight are making only marginal gains.
"The world is gaining weight – that story is true – but it's just not true for everyone," Dr. Fahad Razak, a clinical fellow at the University of Toronto, said in an interview.
"What we have is a vanishing middle: The people with a healthy weight, who have the best health outcomes over time, are disappearing," he added.
Razak, co-author of a research paper published in Wednesday's edition of the medical journal Public Library of Science Medicine, said that what is left at the either end of the spectrum is a growing population of wealthy people whose weight is ballooning but whose ranks are small, and a large and neglected underclass of poor, malnourished people.
"This is just another manifestation of income inequality," he said.
From 1995 to 2010, the number of obese people in the world jumped to 475 million from 200 million. There are now as many overweight people on the planet as underweight ones.
But what the new research shows is that the underweight population is making only tiny gains and, in most low-income countries, malnourishment is a far more significant problem than overnourishment.
To conduct the study, researchers analyzed changes in the body mass index – an approximation of body fat – in more than 730,000 women in 37 low- and middle-income countries from 1991 to 2008.
In India, for example, the number of obese citizens jumped 50 per cent in that period, to 3.6 per cent from 2.4 per cent, while the underweight population fell 20 per cent, to 24.8 per cent from 30.7 per cent.
In Kenya, the outcomes were even more disparate, with the obese group growing to 8.5 per cent of the population from 3.5 per cent, while the underweight group continued to climb to 11.5 per cent from 9.4 per cent.
Being underweight and overweight can both have negative health consequences.
According to research published this year in The Lancet, however, obesity kills three times as many people worldwide as malnutrition. About three million people die of obesity-related causes, while one million deaths result from malnutrition.
Eating too much is now a more serious risk to the health of populations around the world than eating poorly, with the exception of sub-Saharan Africa, according to that study. Deaths from malnutrition are down about two-thirds over the past two decades, while obesity-related deaths have soared in that same period.
Razak said those global numbers mask some issues that are particular to developing countries.
In developed countries like Canada, obesity is a problem often associated with low income: Poorer people eat cheap, starchy foods and are less likely to be physically active. In the developing world, obesity is an issue with the wealthy: Being overweight is often seen as a sign of prosperity.