Public transport commuters have healthier weights than people who drive to work

It is no great surprise that a new study has found that active methods of commuting to work such as walking and cycling are linked to lower body weights and body fat compositions than those who drive. However, the research in question has also found that these health benefits are also shared by people who commute to work by public transport. 

The research was carried out by a team of scientists from the London School of Hygiene & Tropical Medicine and University College London, who were aiming to find clinical evidence linking active commuting with objective measures of obesity.

Previous studies have illustrated the health benefits of physical activity and linked active commuting with a lower risk of obesity. However, self-reporting of weight in adults is known to be prone to bias, and this has been a limitation of previous research.

The researchers analysed data from Understanding Society, the United Kingdom Household Longitudinal Study: a large and nationally representative source of data. They examined a total of 7,534 BMI measurements and 7,424 percentage body fat measurements of both men and women.

Of these participants, the following percentages were reported with regard to methods of commuting to work:

§  Private transport: 76% men, 72% women

§  Public transport: 10% men, 11% women

§  Walking or cycling: 14% men, 17% women.

The researchers found that with regard to BMI and percentage body fat, both the participants who commuted actively and those who used public transport were significantly healthier than those who travelled to work privately.

Men commuting via public or active transport had, on average, a BMI score 1 point lower than men who used private transport - a difference in weight of about half a stone (7 lb). For women, the BMI difference was 0.7 points, equating to a difference in weight of 2.5 kg (5.5 lb).

The difference between people commuting via private transport and people commuting actively or publicly was similar in both size and significance for percentage body fat. These associations were also unaffected when the researchers adjusted their findings to take into account other factors such as age, pre-existing medical conditions and physical activity in the workplace.

These differences are "larger than those seen in the majority of individually focused diet and physical activity interventions to prevent overweight and obesity," report the authors.

The study utilised a reliable source of data that measured its outcomes objectively. However, it is limited by the basic measurement of the participants' diet and the restrictive nature of its options for reporting transportation. Mixed-mode journeys were not captured as participants were asked to report only their main method of commuting. Finally, the study is observational and does not define causation.

In an accompanying editorial, researchers from Imperial College London in the UK suggest that "this benefit is likely to accrue because use of public transport generally involves walking and occasionally cycling to transport access points or interchanges, thus increasing incidental physical activity."

Despite this, they are keen to point out that the commute to work is a great opportunity to increase levels of physical activity and improve physical health. Unfortunately, increased rates of car ownership have correlated with a steady decline in active commuting in most areas of the world since the middle of the 20th century.

The authors acknowledge that further longitudinal research is required to confirm causality, but for now they advise that the use of public transport and walking and cycling in the journey to and from work should be considered as part of strategies to reduce the burden of obesity and related health conditions.

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