The carbon footprints of obesity, chronic disease and population growth: four things doctors can do

It is no accident that the obesity epidemic coincides with signs of climate change. Both phenomena stem from a fundamental and unsustainable imbalance in use of food and other energy by humans that is linked to modern agribusiness and transport systems, and the growing number of people using them.1 A recent review2 estimated that a population with an abnormally high mean body mass index (BMI) and 40% obesity requires 19% more food energy for maintenance than one with a normal mean BMI and 3.5% obesity; the marginal greenhouse gas emissions from food production and car travel associated with the higher level of human adiposity is between 0.4 and 1.0 gigatonnes of carbon dioxide (CO2) equivalents per year per billion people — up to 2.5% of total emissions for 2002.

This year, we reached the point where more than half the world’s population lives in cities. Population growth, and absolute growth in the overweight and obese populations, is occurring most rapidly in developing countries, with rapid urbanisation and uptake of energy-dense diets.3 At the same time, millions have been lifted from poverty, and life expectancy has increased because of better nutrition, as well as access to vaccination and other effective primary health care services.4 Populations of developing countries have historically contributed least to global warming, yet they will likely bear the greatest economic and health burden from it. They will be the most vulnerable to food and water scarcity, environmental degradation and mass migration.5 Globally, at least 200 million women want, but do not have, access to modern contraceptives and, as a result, 76 million unwanted pregnancies occur each year.6

In Australia, ageing, obesity and associated conditions account for the greatest proportion of disability and accelerating health care use. Health care spending approaches 9% of gross domestic product here and in the developed countries generally (except in the United States, where it is much higher), but without a clear relationship with better health outcomes.7,8 The health sector itself has a significant and expanding carbon footprint. For example, the National Health Service in the United Kingdom has calculated its carbon footprint to be more than 18 million tonnes of CO2 per year, 25% of total public-sector emissions.9 In the US, Practice Greenhealth has created an energy impact calculator for hospitals, which allows an understanding of some of the health co-benefits of energy efficiency and on-site energy generation.10

When we add the increasing costs of health care and the health industry’s carbon footprint to the entirely preventable loss of years of life and wellness caused by obesity and physical inactivity, we have a compelling case for specific action led by doctors in four health-related domains.

It has been shown that policies that increase inequity (in income, economic opportunity, education, access to health and other services) also reduce overall health in the whole population, not just in those groups who are directly disadvantaged.17 There are well founded concerns that some proposed strategies (eg, emissions trading) may increase inequities nationally and globally, without necessarily achieving the proposed reductions in carbon and other greenhouse gas emissions.18 The “equity ruler” should be used to balance the likely costs and gains in human health and welfare of all proposed and existing climate change policies. The Stern Review19 suggests that:

The presidents of 10 medical colleges called on governments to act decisively in negotiating a new United Nations Framework Convention on Climate Change in Copenhagen in December 2009.20 They also called on doctors to take the lead in practical steps to effect needed changes. The disappointing outcomes of the Copenhagen summit make the need for action all the more pressing. The four domains for action that I have singled out are precisely those where doctors can and should be leading.