Obesity: not just a disease of the rich

Hi. My name is Ross McManus, and I am a Professor of Molecular Medicine in TCD. My main area of interest is in the genomics of common diseases. In other words, the impact of our genetic inheritance on developing complex conditions, including obesity and inflammatory diseases. In developing countries, traditionally much of the emphasis in health has been on communicable diseases and for good reason. HIV/AIDS, diarrheal diseases, malaria, and TB are among the biggest killers. However, conditions usually associated with more affluent societies, such as overnutrition, overweight, and obesity are becoming more common in developing countries.

For example, ischemic heart disease is a more important cause of morbidity and death, that’s 35 per 100,000 individuals per year, than TB, and not far beyond diarrheal diseases and malaria, which killed 68 and 62 per 100,000 respectively. Seventh on the list in developing countries is type 2 diabetes. And this is an accelerating trend in both adults and children. In 2008, there were conservatively estimated to be over 900 million overweight or obese individuals in developing countries, compared to less than 600 million in affluent countries. By 2030, half the world’s population is expected to exceed normal weight, and a large proportion of these are going to be in the developing world.

So obesity has increased tenfold in China since 1980 to about 8%, and that is a country at the low end of the spectrum. At the high end, it’s gone from between 15% to 40% in Egypt, and the numbers are similar in South Africa. And these rates actually are surpassing those that are found in the USA, for example. So what is the cause of this rise in overweight individuals? Well, it is affected by many factors. Obviously, food intake and decreasing physical activity are foremost amongst them. And these behaviours are greatly impacted by increasing urbanisation and disposable incomes.

If we consider children according to the UNICEF WHO World Bank estimates, overweight and obesity increased across the board in developing countries from 2000 to 2016. However, rates of increase vary greatly on a regional basis. So from about 3% to 4% in Latin America and Africa to staggering increases of 38% in Asia and 86% in Oceania, and this is against a backdrop of burgeoning populations. That means the total number of children affected are increasing at worrying rates. Currently, in total, 6% of the world’s children under the age of five years are overweight or obese. However, if we zoom in, we can see that in North Africa, that is 10% of the child population. It’s 11% in Central Asia.

And 12% of children are overweight in South Africa. That equates to nearly 10 million children in this category in Africa. That’s almost a 50% increase in total numbers from 2000 to 2016. If we look at countries in terms of their incomes, in fact, the rate of overweight children has risen most markedly in low income and lower-to-middle income countries. So the increases there are 37% and 53% respectively, while the rate of increase in high-income countries is a more modest 12%. Now there are more overweight children in countries in the lower half of the income spectrum than in the upper half, even in regions with lower rates of overweight and obesity, such as West Africa.

The overall figures can hide disparages at local levels. For example, between urban and rural communities. Urban communities, as a general rule, have twice the rate of obesity as rural communities in much of Africa. Obesity is, of course, increasing across all ranges, so why do we focus on children? Well, childhood obesity, with rare exceptions, translates to adult obesity. And our likelihood of putting on weight increases as we get older. So overweight is considerably higher in children in the category of five to 17 years of age, where it reaches one in 10 in sub-Saharan Africa.

Indeed, really interesting findings in recent years have indicated that environmental exposures in the womb at early childhood can influence weight gain and associated metabolic disease in later life. These diseases include a whole raft of health problems, including cardiovascular disease, metabolic syndrome, and type 2 diabetes. These are referred to as complex diseases, because they have many causes, thus making it difficult to understand and combat. This is another reason why there have been less of a focus on communicable diseases. However, they are now a major focus of research right around the world and here in Trinity. Diseases associated with excessive weight are already significant causes of ill health in developing countries.

So hypertension is on the increase, affecting up to half of adults in some West African cities. A recent review states that prevalence of type 2 diabetes is in West Africa ranges from 2.5 to 10%. And the International Diabetes Federation predicts a 98% increase in the region by 2013. That’s only 13 years away. This is in a region with comparatively low prevalence at present. So health challenges in developing nations are not just about infectious diseases. Ongoing research has shown that the non-communicable diseases, such as overweight and obesity, not to mention the even bigger problem of under-nutrition, this is the so-called double burden of malnutrition, these nutrition-associated diseases are serious problems.

Overweight obesity is an epidemic of worldwide concern and a key challenge for SDG3, posing maybe even a greater threat for developing than affluent nations. It is really important that not only do rates of increase slow down, but they must be thrown into reverse. And children need to be a particular focus of attention.