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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.

Obesity and alcohol-bad for your liver and worse in combination

Ami Banerjee
Last edited 22nd March 2010

After smoking, alcohol is the next public health behavioural challenge of our generation. There have been moves at national and international level to recognise and tackle the problem of alcohol misuse. Its consumption is increasing, particularly among younger adults.

Alcohol consumption increases risk of liver disease. However, levels and patterns of alcohol consumption do not fully explain the rises in liver disease mortality that have occurred in some countries.

A recent Scottish study showed that body mass index(BMI) is related to liver disease, suggesting that the current rise in overweight and obesity may lead to a continuing epidemic of liver disease. Looking in the same cohort of men in Scotland, the same authors found that raised BMI and alcohol consumption are both related to liver disease, with evidence of a supra-additive interaction between the two. This led the study authors to suggest that BMI-specific "safe" limits of alcohol consumption may need to be defined. In the same issue of the BMJ, a study of 1.2 million middle-aged women in the UK showed that 1800 of the women developed or died from liver cirrhosis during follow-up. Increasing BMI was associated with increased liver cirrhosis, with a 28% increase in risk for every 5 unit increase in BMI. In addition to the effect of BMI, the absolute risk of liver cirrhosis increased as alcohol intake increased. The authors estimated that 17% of liver cirrhosis is due to excess body weight, compared to 42% due to alcohol.

An accompanying editorial makes the point that “compared with the risk of cardiovascular events in middle aged people, an absolute risk of one case per 1000 people over five years for liver cirrhosis seems low. However, this absolute risk still represents a substantial burden of illness for the patients concerned and for the health service”. The upshot is that alcohol and obesity in combination cause liver cirrhosis, another negative consequence of unhealthy lifestyle. Reductions in alcohol consumption and obesity are currently the only way we can prevent non-viral liver disease.

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