Schemes that promote cycling seem to have limited benefit

Boris bikesCity wide programmes that promote cycling – such as London’s new bike hire scheme – seem a great way to get the public active and tackle the obesity epidemic. But new research published in the BMJ suggests that interventions to promote cycling don’t have much discernible effect after all.

Public health programmes that specifically aimed to increase cycling in a population found increases the the proportion of trips made by bike or the number of bike trips per person of 3.4 percentage points at the most, whereas there was little evidence that cycling increased physical activity or reduces obesity population wide.

Adults in the UK are supposed to at least 150 minutes of moderate intensity physical activity or 75 minutes of vigorous physical activity a week, but few manage. Cycling can fit relatively easily people’s daily routines as a means of travel from place to place, so people might be more inclined to adopt and maintain this type of physical activity than something like running or swimming. Also, if people cycle rather than take the bus or get in their cars, they’re helping to reduce harmful traffic pollution – so cycling could help the environment as well as provide a double whammy of health benefits.

The authors of this paper looked at 25 controlled or “before and after” studies on the effect of various different cycle schemes, such as free bike programmes, building new cycle routes, and promoting cycling to families. The studies were from seven countries, including the UK and the US.

Six studies assessed programmes that specifically aimed to promote cycling, of which four – an intensive one-to-one scheme for obese women, improvements to a cycle route network, and two multifaceted cycle promotion initiatives at town or city level – were found to be associated with increases in cycling. For example, one study found that improving the connectivity of the cycle route network in the Dutch city of Delft increased the proportion of household trips made by bicycle from 40% to 43% over a three year period compared with a change from 38% to 39% over the same period in an area where no improvements had been made.

A further 16 studies evaluated individualised marketing of “environmentally friendly” modes of transport (walking, cycling, and public transport) via marketing and incentives such as free bus tickets. On average this approach increased the number of cycling trips each individual made by eight a year.

Three other studies examined the effects of efforts to change travel behaviour in general, such as car sharing schemes. Two of these trials found small increases in the proportion of trips made by bicycle or the frequency of cycle trips per person (+1.1 and +0.17 a week, respectively), whereas the third actually found a decrease in the proportion of bike trips of almost 12%.

Only two of the 25 studies assessed looked at the health benefits of schemes to promote cycling, one of which reported a small but positive shift in the amount of overall physical activity in the population studied.

Discussing their less that glowing findings, the authors write that “There is nevertheless a strong case for promoting cycling on health grounds,” pointing to evidence that at an individual level cycling to work or school has been shown to improve cardiorespiratory fitness and reduce mortality. “Promoting cycling is, therefore, a viable approach to improving health,” they conclude.
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Yang L et al. (2010) Interventions to promote cycling: systematic review. BMJ 341:c5293. DOI: 10.1136/bmj.c5293

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Obese children are at high risk of death before middle age

childhood obesityA study published in the New England Journal of Medicine has found that children who were obese were almost twice as likely to die before 55 years of age than those who were not obese. Moreover, children whose weight was in the top 25% out of nearly 5,000 kids were 2.3 times more likely to die from diseases before middle age than those whose weight fell in the bottom 25%.

The authors of this big, long study looked at body mass index (BMI; a measure of weight that takes into account a person’s height) and risk factors for cardiovascular disease in 4,857 children aged 5-19 years who lived on an American Indian reserve in Arizona.

BMI and markers of cardiovascular disease were measured in all children when the study started in 1966 or after. The participants were then followed up until their death, their 55th birthday, or the end of 2003, whichever came first.

A total of 559 (11.5%) participants died before the age of 55, 166 (3.4%) of whom died from a disease or from self inflicted injury such as alcohol or drug abuse – so-called “endogenous causes.”

Children whose BMI fell within the top 25% of all those in the study were 2.3 times more likely to die from endogenous causes before the age of 55 than those whose BMI was in the lowest 25%. In fact, each one unit increase in BMI increased the risk of early death from endogenous causes by 40%.  This relationship persisted but at a slightly lower level once factors like cholesterol level and blood pressure were taken into account.

The authors then looked specifically at the 1394 (28.7%) children who were obese – those whose BMI fell in the top 5% on growth charts from governmental public health body the Centers for Disease Control and Prevention. Compared with non-obese children, these kids were 31% more likely to die before they reached 55.

Children with high blood glucose levels – a sign that diabetes might be on the horizon – were at 73% higher risk of dying early, whereas those with hypertension were at 57% higher risk. This link prompted the authors to say that the link between obesity and premature death “may be partially mediated by the development of glucose intolerance and hypertension in childhood.”

Childhood cholesterol level and blood pressure, however, had no effect on the risk of premature death from endogenous causes.

Speaking to the New York Times, senior author Helen Looker said, “This suggests that obesity in children, even prepubescent children, may have very serious long-term health effects through midlife — that there is something serious being set in motion by obesity at early ages. We all expect to get beyond 55 these days.”

American Indians were studied because childhood obesity has been common for decades in this ethnic group. The prevalence of obesity in young Arizona Pima Indians in the 1960s, when this study was initiated, was similar to that seen in Hispanic and African American children today, so hopefully the results from this long study should be generalisable to kids today.

In a linked editorial, Edward W Gregg of the Centres for Disease Control and Prevention pointed out: “Since the trends with respect to obesity and diabetes among the Pima Indians have been a reliable harbinger for trends in the rest of the U.S. population during recent decades, the present study should intensify the debate about whether interventions that are initiated during childhood and young adulthood can affect our broader diabetes epidemic.”

Furthermore, in a previous study the same authors found that BMI correlated closely with total body fat – adiposity – and that adiposity in turn correlated with cardiovascular risk factors. By extension, the link between BMI and early death in this study suggests that actual body fat is linked with early death.

This is important because BMI is an imperfect measure of weight – for example, some very muscular people might be heavy for their height and thus have a high BMI – thus despite the study results weight might not genuinely be associated with early death. On the other hand, high adiposity – “fatness” – is a more indicative of an unhealthy weight.

“Childhood obesity is becoming increasingly prevalent around the globe. Our observations, combined with those of other investigators, suggest that failure to reverse this trend may have wide-reaching consequences for the quality of life and longevity,” conclude the study authors.

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Franks P et al. (2010) Childhood Obesity, Other Cardiovascular Risk Factors, and Premature Death. New England Journal of Medicine 362 (6): 485-493. DOI: 10.1056/NEJMoa0904130

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Cycling or walking to work reduces risk of obesity and cardiovascular disease… but only in men

Cycling to workOK, so it seems pretty obvious that cycling or walking to work is better for you than taking the car. New research published in Archives of Internal Medicine has clarified the beneficial effects in terms of fitness and cardiovascular health of walking or cycling to work – but they’re largely only seen in men.

This study assessed 2,364 adults from four US states, and found that less than a fifth (16.7%) used active means to get to work. Men who walked or cycled to work were fitter (able to run for longer on a treadmill) and were less likely to be obese (had a lower body mass index) than those who commuted by car, bus, train or subway.  Female active commuters were fitter than their more sedentary counterparts, but no less likely to be obese.

In addition, men who walked or cycled to work were at lower risk of cardiovascular disease, as they had lower levels of a range of cardiovascular disease biomarkers (i.e. blood levels of triglycerides and fasting insulin, and diastolic blood pressure).  This inverse correlation was not seen in women though.

So why the difference between men and women?  Well, women were less likely to be active commuters (15.6% of women versus 18.0% of men), and those who were active commuters were more likely to walk than cycle (82.8% in women versus 64.1% in men).  Although the median distance to work for active commuters was 5 miles for both men and women, men would cycle or walk up to 13.5 miles whereas the maximum commute in women was 10 miles.  It seems that women need to commute a bit further and at a higher intensity of exercise in order to see weight and cardiovascular benefits of active commuting.

The authors of this study conclude that nonleisure forms of exercise such as active commuting can help people increase their levels of physical activity and have beneficial effects on health.
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Penny Gordon-Larsen, Janne Boone-Heinonen, Steve Sidney, Barbara Sternfeld, David R Jacobs Jr, Cora E Lewis (2009) Active Commuting and Cardiovascular Disease Risk: The CARDIA Study. Arch Intern Med 169(13): 1216-1223. PMID: 19597071

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Government to tackle obesity with Change4Life campaign

Change 4 LifeI recently blogged about the alarming rates of obesity among children in England, with one in four 4-5 year old children and one in three 10-11 year olds in this country obese or overweight. The Foresight report, published in 2007, ominously predicts that by 2050 90% of British children will be overweight or obese.

The British Government has now responded to this issue by launching a huge campaign to persuade the population to switch to a healthier lifestyle. The Change4Life strategy will promote the message “eat well, move more, live longer” on TV, in the press, on billboards and online initially for 3 months, and will continue over 3 years.  The initiative will be supported by £200m of advertising and marketing donated by food companies such as Tesco, Mars, Nestlé and Flora.

Dawn Primarolo, minister for public health, said today: “We are trying to create a lifestyle revolution on a grand scale. There are very serious health consequences with allowing dangerous quantities of fat to build up in our bodies. This is not just an ad campaign – we are calling it a lifestyle revolution – it is a long-running concerted effort to change behavior.”

The television campaign launches on Saturday 3rd January with adverts designed by Aardman Animations, the people behind the much loved plasticine duo Wallace and Gromit.  The engaging clip is designed to warn viewers of the health risks associated with being overweight and is targeted at helping young families change their lifestyle for good.

Change4Life is the biggest Government campaign ever launched and is expected to follow in the success of similar cross-media anti-smoking initiatives.  Unlike anti-smoking public awareness strategies though, this campaign steers away from shock tactics and instead offers practical advice.

Critics have been quick to point out that the involvement of food companies in the campaign is a way for such corporations to cast their brand in a healthy light without actually changing the salt or fat content of their food.  Tam Fry of the National Obesity Forum warned that junk food companies were donating millions to the campaign as a way of heading off the “regulation they fear”.

The Telegraph notes that “neither the leaflets nor the screen advertisements use the word obesity”, preferring instead to state that children could grow up to have “dangerous levels of fat in their body”.  The campaign is designed to avoid pointing the finger at any one group, however, specifically avoiding talking about ‘fat bodies’ and blaming modern life rather than parents.

Let’s hope that the more kindly, blame-free approach of Change4Life gets the people of the UK off the sofa and helps to avert our obesity timebomb.

  • If you’re skeptical, the Big Question in The Independent casts a critical eye over the Change4Life campaign, asking whether the Government can really make us eat less.
  • On the other hand, it you want to get serious about improving your lifestyle there is stacks of information on how to eat better, move more and live longer on the Change4Life website.
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More than 20% of English primary school children are obese or overweight

obesechild460One in four 4-5 year old children and one in three 10-11 year olds in England are obese or overweight, according to data from the 2007/08 National Child Measurement Program published by the NHS Information Centre.  The North East, the West Midlands and London are particular obesity blackspots, and boys are more likely to be obese than girls.

The National Child Measurement Program, established in 2005, weighs and measures school children in Reception (3-4 years old) and Year 6 (10-11 years old) to assess the level of overweight and obesity among kids in England. Almost a million primary school children were measured in the 2007/08 survey, representing 88% of those eligible.

The 2007/08 survey found that 22.6% of 3-4 year old children and 32.6% of 10-11 year olds were overweight or obese.  Almost twice as many Year 6 children were obese compared with Reception-age kids (18.3% vs 9.6%), and boys were significantly more likely to be obese than were girls.

The prevalence of obesity among primary school kids in both age groups was significantly higher than the national average in the North East, West Midlands and London.  In addition, there was a high prevalence of obesity in Reception-age children in the North West and Year 6 children in Yorkshire and Humber.  The South East Coast, South Central, South West and East Midlands regions, on the other hand, had lower-than-average rates of obesity among schoolchildren.

Obesity rates in 2007/08 seem similar to those in the 2006/07 survey (9.9% among Reception-age children and 17.5% in Year 6 children); however, the National Child Measurement Program report cautions that the prevalence of obesity among Year 6 children might have been underestimated by as much as 1.3% in 2006/07 due to children opting out of being measured.

The British Heart Foundation responded to these results by calling for several measures to tackle childhood obesity, including tighter regulation of junk food marketing, consistent and simple food labelling, and more funding to help children get involved in physical activities.  Saranjit Sihota, Head of Public Policy at Diabetes UK, likewise called for more action to tackle the epidemic – remarking that “This new data confirms the shocking state of children’s health in this country” – and pointed out that said that there is a clear link between obesity and Type 2 diabetes.

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