What does obesity mean for individual and population health?

It’s no secret that overweight and obesity are a modern epidemic. They are associated with many adverse health outcomes and are therefore an important issue in the realms of both individual and public health. Articles published in this issue of the Journal remind us not only of these realities but also that we still have a long way to go in understanding the links between obesity and poor health. In this issue, we look at the role of exercise in maintaining health, and at obesity from childhood through adolescence and into the reproductive years.

In unpicking the relationship between body mass index (BMI) and poor health outcomes, Green and Maiorana (doi: 10.5694/mja11.11055) make a strong case that exercise and fitness are better than obesity for predicting cardiovascular and all-cause mortality: improved fitness has benefits that are independent of weight reduction. They acknowledge that there is a place for bariatric surgery, as outlined by Proietto last year (MJA 2011; 195: 144-146), but believe that exercise and fitness should not be forgotten. Exercise should be prescribed because in itself it is good for you, regardless of weight loss. The authors argue that, if emerging indications of epigenetic influences on lifelong weight control are borne out, the need to acquire good exercise habits at a young age is vital.

Skouteris and colleagues (doi: 10.5694/mja11.11015) observe that it does indeed seem to be good to start young. They look at existing guidelines for physical activity in preschoolers (what would our grandmothers have thought of guidelines for preschoolers?), and acknowledge that we really have no idea about appropriate guidance. Guidelines are inconsistent, and their basis uncertain. Furthermore, there is a lack of information about what is a normal level of activity, and a lack of knowledge about what activity (moderate or intense?) should be measured and how to measure it.

Nearly one in four Australian adolescents are overweight or obese, according to Morley and colleagues (doi: 10.5694/mja11.11184). Being male, less wealthy, inactive, sleep-deprived and frequently hooked to a computer or TV is characteristic of those at highest risk. The most important factor was found to be low socioeconomic status, but the way this is associated with obesity is still to be ascertained. One thing Rissel and colleagues (doi: 10.5694/mja11.10873) have confirmed is a significant association between soft drink consumption and obesity in school students.

McIntyre and colleagues (doi: 10.5694/mja11.11120) argue that overweight and obesity are now endemic in pregnant women. They found that, despite some missing data, the overall prevalence of overweight and obesity had increased little over a decade, but the obese had become more obese. In a large cohort, about one in 20 pregnant women had a BMI of 35 kg/m2 or higher. As with adolescents, obesity was associated with lower socioeconomic status. The authors confirm that being overweight or obese confers significant maternal and neonatal risk, requiring more obstetric resources. From an obstetric point of view, it is challenging to care for people who are this large, and more challenging to safely deliver their babies. Women need to know that obesity, like tobacco and alcohol, is a risk factor in pregnancy.

Despite all the unknowns in our understanding of overweight and obesity, the simple principle of energy in and energy out should underpin much of our thinking. Magarey (doi: 10.5694/mja12.10103) provides some practical suggestions for redressing the imbalance between food consumption and exercise that is so prevalent in our society. If we want our children to enjoy a long and healthy life, we need to work on this equation.