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Can a virus ever make you fat?

Ami Banerjee
Last edited 24th September 2010

On both sides of the Atlantic, obesity, particularly in childhood, is a growing problem (no pun intended). So earlier this week, when new research claimed to associate a virus that causes the “common cold” with the development of obesity, the media took interest in both the UK and the US.

Jeffrey Schwimmer, lead researcher was quoted on the BBC:
"It is time that we move away from assigning blame in favour of developing a level of understanding that will better support efforts at both prevention and treatment. These data add credence to the concept that an infection can be a cause or contributor to obesity.”

That is big chat. Like all papers published in major journals, the abstract or summary of the paper is available on PubMed for free. I used the abstract to examine these claims a bit further.

The authors set out to compare blood levels of antibodies to adenovirus (AD36) in children who were obese versus those who were not. The first problem is that they did a “cross-sectional study”, which means they took a snapshot of their patients at a single point in time, rather than following them up over a length of time. That means that we deduce nothing about the virus (the “exposure”) causing obesity (the “outcome”) since we are not following the children up over time from the onset of the infection of the virus. At best, we can talk about an association or a link. Secondly, they have kids from 8-18 years of age. Children at eight are very different to children at eighteen and so you might expect the effect of infection at different stages of childhood to be different. So why are they lumping all kids of all ages together?

In the results, only 124 children were studied, and we have no idea how many patients were excluded from original recruitment. Half of the 124 children were obese. Before we go any further, the antibody (AD36) was present in 15% of the children. In other words, any comments made about the relationship between the antibody and obesity is based on 19 children. That does not seem a big enough number to be making any claims.

The paper’s main findings are: “The majority of children found to be AD36-positive were obese (15 [78%] of 19 children). AD36 positivity was significantly (P _ .05) more frequent in obese children (15 [22%] of 67 children) than nonobese children (4 [7%] of 57 children)”. Again, we are looking at only 19 children who had viral antibodies. In addition, the p-value is only just statistically significant (p=0.05). You do not have to read the whole paper to see the limitations of research. Bottom line: regular Big Macs and lack of exercise are still much more likely to cause obesity in childhood than the common cold.

If you’re reading this you’re probably thinking what has cross promotional marketing to do with children. Personally when I first heard the term I was thinking what exactly is it?

Simply, cross-promotional marketing is the act of strategically aligning businesses that target the same market but do not directly compete with each other. Whenever two organizations join forces to attract their mutual customers they can more than double the number of prospects they each reach.

For example, in 1996 MacDonalds and Disney signed a ten year deal to cross-promote. Get it? Same market, but not in direct competition and double the reach. A subsequent survey by Eric Schlosser of US schoolchildren found that the only fictional character with greater recognitions than Ronald MacDonald – who had 96% recognition – was Santa Claus. Oh, by the way, MacDonalds operates more playgrounds – designed to attract children and their parents to its restaurants – than any other private entity in the US;

This sort of promotion is also seen with film tie-ins such as Burger King and Toy Story.

Sorry to be a spoilt sport, but given the obesity epidemic - currently 10% of children worldwide are either overweight or obese - it’s time to rethink cross-promotion.

Beware; next time you are out and about, particularly if you have children, you will start to see cross-promotion all around you.

After Christmas and in the run-up to Lent, people are often thinking about New Year’s resolutions and what to give up. One of the most common excesses that people want to address is food. This is the most common time of year to start new diets, exercise regimes and gym memberships, and yet obesity, particularly in childhood, is on the rise. The direct cost of overweight and obesity to the NHS has been estimated at over £3 billion. Inequalities in obesity have been identified between North and South, between men and women, and between social classes, and these inequalities seem to be worse for childhood obesity.

With the big public health problems of our age, whether smoking and high blood pressure, or diabetes and obesity, there are health inequalities, but there are also cheap, simple, population-wide interventions which can save thousands, if not millions, of lives. In the case of childhood obesity, it is not rocket science- healthier diet, less processed food, more exercise, and there are signs that the childhood obesity epidemic is levelling off. However, there is a constant push by device companies and drug companies to offer more complicated solutions which will produce big profits for them in these disease areas, because they affect so many people in the population.

This week’s BMJ includes a randomised controlled trial of a novel computerised device, the Mandometer, which provides feedback to participants during meals to slow down speed of eating and reduce total food intake. The trial ran for 12 months comparing the Mandometer with standard lifestyle modification advice and included 106 obese people aged 9 to 17 years. The Mandometer group had a BMI 0.24 units lower than the group receiving standard care. Not only does this seem a paltry difference in BMI; two of the study authors own 60% of the company which produces Mandometer, and so it is unsurprising that they found a positive effect for their device. It is hard to envisage a world where this device is going to be widely used or where it is going to make any difference to childhood obesity. If widely used, such devices will at best only increase the socioeconomic inequalities which already exist in childhood obesity. Surely the simple, population-wide policies of encouraging more exercise and better diet should be promoted instead?

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