Commuting and BMI: What Is the Link?

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Cycling, walking, or public transit to work may help fight obesity.
Cycling, walking, or public transit to work may help fight obesity.

Getting to work by cycling, walking, or taking public transit was linked to a lower BMI for people in their 40s, according to results from a large observational study in the United Kingdom.

The greatest difference in BMI occurred between cyclists and drivers, but researchers found that people who walked also had significantly lower BMI (See Tables 1 and 2). The association held even for those who combined activity with driving or taking public transit, and researchers noted that active commuters also had lower body fat.

“Broadly, we found that those who used active modes of transport, walking, cycling, and mixing walking and cycling with bus or train use, had significantly lower BMI and percentage body fat compared with the more sedentary car users,” Ellen Flint, PhD, a lecturer in public health at the London School of Hygiene and Tropical Medicine, said during a podcast interview. She conducted the study along with her partner Steven Cummins, PhD, also of London School of Hygiene and Tropical Medicine.

Dr Flint added that energy intake appeared to have to no effect on the findings.

The results were published in The Lancet Diabetes & Endocrinology.

Using baseline data from the UK Biobank, researchers conducted a cross-sectional, observational study to explore the connection between commuting method and midlife obesity. There were 2 analytical samples, 1 for BMI (n=72 888 men; n=83 667 women) and 1 for body fat (n=72 139 men; n=82 788 women).

Participants aged 40 to 49 years were asked to select 1 or more method of commuting: driving a car or other motor vehicle, walking, public transport, or cycling. Overall, 23% of men and 24% of women engaged in some degree of active commuting.

Table 1: BMI compared with car-only men

Cycling –1.71 kg/m² (95% CI, –1.86 to –1.56)
Walking –0.98 kg/m² (95% CI, –1.2 to –0.76)
Public transit –0.7 kg/m² (95% CI –0.83 to –0.57)
Combined active/public transit –1.00 kg/m2 (95% CI, –1.14 to –0.87)


Table 2: BMI compared with car-only women

Cycling –1.65 kg/m² (95% CI –1.92 to –1.38)
Walking –0.8 kg/m² (95% CI –0.94 to –0.66)
Public transit –0.7 kg/m² (95% CI –0.83 to –0.57)
Combined active/public transit –0.67 kg/m2 (95% CI, –0.86 to –0.47)

Additionally, body fat percentage was lower in both men (–1.32%; 95% CI, –1.53 to –1.12) and women (–1.1%; 95% CI, –1.4 to –0.81) who combined public transport with active commuting methods compared with car-only commuters. Similarly, results were seen among cycling or cycling and walking vs car-only in men (–2.75%; 95% CI, –3.03 to –2.48) and women (–3.26; 95% CI, –3.8 to –2.71).

Dr Flint said that she and Dr Cummins looked specifically at commuting because obesity has risen as the amount of active travel has decreased.

“We know that physical activity can help prevent obesity, yet two-thirds of the UK population don't achieve recommended weekly levels of physical activity,” she said. “The commute to work is a point at which we could intervene to increase the amount of physical activity that we do that is easily adopted, quite feasible, and doesn't require any greater time or money expenditure.”

Writing in an accompanying editorial, Lars Bo Andersen, PhD, of Sogndal and Fjordane University College said that these results show that active commuting can be a way for people to incorporate exercise into their daily routines. He added that the findings have important implications for city planners and government officials.

“The study of Flint and Cummins suggests active commuting can prevent obesity, but many other health benefits could be gained with a more cycle and walking friendly environment,” Dr Andersen wrote. “Promotion and facilitation of active commuting should be part of national and global strategies for the prevention of obesity, and it should be mandatory for policymakers and planners to take cycling and walking facilities into account.”

References

  1. Flint E, Cummins S. Active commuting and obesity in mid-life: cross-sectional, observational evidence from UK Biobank. Lancet Diabetes Endocrinol. 2016. doi:10.1016/
  2. S2213-8587(16)00053-X.
  3. Andersen LB. Active commuting: an easy and effective way to improve health. Lancet Diabetes Endocrinol. 2016. doi:10.1016/ S2213-8587(16)00077-2.
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