*Annalijn Conklin  has completed her PhD in Medical Science at the MRC Epidemiology Unit. Picture credit: http://www.freedigitalphotos.net and Stuart Miles.
The "obesity crisis" has been given much media attention in recent months for two important reasons: there are many more people who are overweight and obese now than a generation ago in most countries worldwide, and there is a rising trend that is more than experts previously predicted. The UK in particular has the highest levels of obesity across Europe which has trebled in the last 25 years, while Mexico has the highest rate of increase in levels of obesity across the globe. Carrying extra pounds has many health consequences which create a heavy burden on the individual as well as their families and society more broadly. So, there is indeed a great need to raise public awareness about the importance of keeping a healthy weight and how governments and care providers can support people in doing so.
The causes reported in the media and elsewhere often focus on an individual's balance between the energy consumed and the energy expended. And it is the consequences for national welfare, particularly for cost-constrained healthcare systems, that place obesity and its causes high on the agenda of policymakers. However, experts and researchers in the area recognise that the causes of obesity are complex and extend beyond an individual's lifestyle choices related to diet and physical activity. Both sleep and stress are known to influence a person's weight, but much less attention is given to these factors and to initatives that tackle them such as stress management.
More importantly, obesity is a prime example of a social inequality in health because not all social groups have the same levels, or rates of increase, of obesity. For example, there are strong and consistent educational differences in obesity levels such that lower educated groups have a higher proportion of individuals who are obese.
However, even when individuals share similar levels of education (or social class or wealth), they may differ in their experience of everyday financial troubles. One of the largest drains on disposable income, especially for older people, is paying bills and affording adequate food and clothing. Yet both policy and health research give little attention to how financial hardships may be a unique determinant of obesity.
Recent research on British adults aged 50 and over showed that different types of financial hardship were more strongly correlated with the likelihood of obesity than education, social class or home-ownership. Findings also showed important differences between women and men in which type of financial hardship was most related to which type of obesity. In women, both body mass index (general obesity) and waist circumference (central obesity) were most likely to be highest when they reported the greatest level of difficulty paying bills. In men, greatest difficulty paying bills was most strongly related to a higher odds of general obesity while having less than enough money for needs was most strongly related to a higher odds of central obesity. Moreover, among adults employed in the British civil service, women but not men were more likely to gain excess weight (≥5 kg) when they experienced insufficient money for food or clothing at least twice or more over 11 years, after considering their education, employment grade and home-ownership. This study also found the relationship between financial hardship and excess weight gain remained robust to possible explanatory factors such as diet, physical activity, smoking and alcohol consumption.
Overall, current evidence indicates that public health policies need to consider the role of different types of financial hardship as part of strategies to support women's and men's effort to achieve or maintain a healthy weight. The research suggests, furthermore, that strategies to tackle obesity must address additional pathways of influence beyond energy balance.
Difficulty paying bills or frequently insufficient money for food or clothing is a bigger problem than simply an everyday financial trouble. A recent Science article indicates that financial concerns block cognitive function among poor individuals and that the impact of consuming more mental resources was comparable to losing a full night of sleep. Thus a considered approach to novel interventions could have significant health benefits.