Under the Microscope:There are now more overweight people than hungry people in rapidly developing countries. This rather surprising fact is reported by Barry M Popkin in the September 2007 issue of Scientific American,writes Prof William Reville
As a consequence, obesity is a more serious health risk than hunger in most of these nations. Traditionally, under-nutrition was a serious health risk in these countries, but a dramatic change driven by globalisation has occurred over the past 20 years.
Popkin reports that in countries such as Egypt, South Africa and Mexico more than half the adults are either overweight or obese. These weight categories are defined by body mass index (BMI). BMI is calculated as your body weight in kilos divided by the square of your height in metres. A BMI of 25 to 29 is defined as overweight and a BMI of 30 and above as obese. These criteria are very strict at the lower limits - for example someone with a BMI of 26 will scarcely look overweight and, so, the obesity statistics quoted above may not be quite as alarming as they seem. Nevertheless it is clear that a serious problem exists, and it is growing. Obesity correlates with diabetes, heart disease and other illnesses and a public health crisis is threatened for these economies.
Popkin homes in on Mexico as a specific example. Fewer than 10 per cent of Mexicans were overweight in 1989, but surveys in 2006 showed that 71 per cent of Mexican women and 66 per cent of men were overweight or obese (these figures rival the figures in the US). In 1989, diabetes was very rare in Mexico but today almost one seventh of the population suffers from adult-onset (Type Two) diabetes and diabetes is spreading fast.
Over the past 20 years, living styles have changed dramatically in countries such as India, Mexico, China and the Philippines. Supermarket chains have spread to those regions and as average incomes rise poorer people have adopted dietary and exercise habits that lead to obesity - consuming sugary soft drinks and foods, watching TV, riding motorbikes instead of walking, and buying convenient processed foods from supermarkets.
People are now consuming much more energy-dense food such as vegetable oils and food derived from animals (meat, fish, eggs and dairy products). The combination of a more sedentary lifestyle and high-calorie food intake has precipitated an obesity problem that is concentrated in the poorest sections of these societies where access to education that would promote healthy eating and exercise is severely limited.
Popkin describes the interesting hypothesis that obese people in these countries may be more susceptible to developing diabetes or high blood pressure than obese people in the developed world. The argument is that populations in Latin America, Africa and South East Asia carry a disproportionate number of "thrifty genes" that evolution selected in order to help survival during famines by enabling people to store fat more efficiently in times of plenty. Unfortunately when high calorie food becomes freely available, a person with these genes efficiently accumulates fat around the heart and liver, increasing the risk of diabetes and heart disease. Popkin reports that nearly one third of people in China, where obesity is sharply increasing, suffer from high blood pressure.
People in these regions are rapidly switching from their traditional low-fat, high-fibre diets to calorie-rich fats, sweeteners and refined carbohydrates. One of the biggest contributors to obesity is the sweetened beverage. Over most of our evolutionary history, after weaning, the only beverages we took were breast milk, and water. Water has no calories and we never evolved mechanisms to automatically reduce food intake to compensate for beverage consumption. Up to 50 years ago the average proportion of dietary calories contributed by beverages was small but this is no longer the case as sugary soft drinks have spread everywhere on earth. The average Mexican now consumes more soft drinks than the average US citizen.
Other key contributors to obesity are energy-dense foods such as vegetable oils, meat, fish, eggs and milk. Technological advances and government subsidies in the production of oilseeds have made vegetable oils cheap. And most of the growth of the world production of meat, fish and dairy produce has come from these nations and this is injecting excessive amounts of saturated fat into the average diet thereby greatly increasing the risk of cardiovascular disease.
Globalisation means the free movement of capital, technology, goods and services around the world and is the main driver of the changes in diet and lifestyle described in this article. Of course globalisation also confers benefits on many of these countries such as encouragement of trade, introduction of technology, improvement in employment, and so on, but unfortunately there are many negative effects such as the obesity problems described in this article. Remedial measures must be put in place to reverse these negative effects.
Unless strong preventive policies are implemented the medical costs of obesity-related illness could topple the economies of China, India and other rapidly developing countries. China already spends six per cent of its GDP on nutrition-related chronic diseases. Popkin suggests restructuring the huge agricultural subsidies that encourage the production of meat and dairy products, thereby encouraging farmers to grow fruit and vegetables. New policies should also promote the consumption of more whole grains, with their enhanced fibre, vitamins and minerals, as opposed to refined carbohydrates. Taxes should be imposed on caloric sweeteners in order to discourage their consumption.
• William Revilleis associate professor of biochemistry and public awareness of Science Officer at UCC - www.understandingscience.ucc.ie