Slashdot Mirror
Obesity Contagious?
An anonymous reader writes "University of Wisconsin-Madison researchers have found that certain human viruses may cause obesity, and by extension make being severely overweight a contagious condition. 'It makes people feel more comfortable to think that obesity stems from lack of control,' the lead researcher says. 'It's a big mental leap to think you can catch obesity.' But other diseases once chalked up to environmental factors, like stomach ulcers, are now known to stem from infectious agents."
There are some staggering data in there regarding the extent to which humans mimic the behavior of similar others. For example, there are statistically significant increases in the number of teenage-couples killed in car accidents among those teenage-couples who recently heard about accidents where teenage couples were killed. The increase is not observed in teenage-couples who didn't hear about the recent accidents, and is not observed among singleton teenagers or older couples who have been exposed to the news. These results have been repeated with a wide range of demographic groups, on a wide range of phenomena, and have been found to be consistent and strong. Hmm, notice a rash of mine accidents recently? Yes, I'm sure it's media focus-bias to some extent...
I really urge you to check that book out if you're interested in the instinct-level mental processes that control us without our being aware of them, or if you want to be..ah...evil?
Look, the cause of obesity is really very simple: the human body (and its ancestors) evolved in environments in which food was scarce, and during that time mechanisms came into being which helped to deal with that scarcity. As a result, it has built-in mechanisms to ensure that there will be sufficient energy store for the body to use for all but the most drastic of food shortages. These mechanisms include the fat store, the tendency for fat to accumulate much more easily than it's used, and an appetite control mechanism that encourages overeating (since who knows when the next meal will become available?).
Now take the human body and put it into an environment where all the food one could ever want is easily available for the taking (all it requires is a small amount of money). What do you expect will happen?
Well, duh...the body will behave as it always has: under the assumption that while food might be plentiful now, it's not likely to be plentiful for long, so better stock up now while it can.
And thus, obesity.
And the reason obesity is so difficult to deal with, and why sustained weight loss has such a lousy track record (95%+ failure rate), is simple: to fight obesity, you have to fight your own body's instinctive drive to "save up for a rainy day".
Use 'slashdot stuff' in the subject line in any email you send me if you want to get past the spam filter.
"What they will conveniently forget is convervation of energy: The only way someone can gain weight is by eating too much... End of discussion".
Unless you are an expert on human metabolism, you cannot possibly make such an assertion. And if you were, you wouldn't.
What you overlook is that human beings are animals, and hence complex biochemical factories, not simple heat engines. If you know how much petrol a car engine of a given capacity burns in a given time, you know how much energy it produces, right? (Even this is only broadly true). But animals are very inefficient converters of energy. I forget how much of the energy we use gets "wasted" as heat, but it's a large fraction. (Just as well, or we'd die of hypothermia). Other energy goes into running various chemical reactions, not all of which are necessarily indispensable or even useful.
As soon as you think about if for a few seconds, it's clear that the body has a lot of discretion in just how it uses the 200 calories you get from, say, eating a bun. These viruses could jam the "make fat" control hard over against the end stop.
Maybe you think it is fine for one person to eat 2900 calories a day, do little exercise, and stay thin; while another person eats 2000 calories, walks six miles and gains weight. But how is the second person going to control their weight in the long run? The only practical way we have of controlling calorie intake is our appetite. Have you ever tried measuring your exact calorie intake while eating a normal diet? It's far from easy. Moreover, how are people to know how much they should be eating, if it's 2000 for one person and 3000 for someone else of similar size, shape, and exercise habits? We can't all become dietary scientists, walking about with computers and clipboards, weighing every bite of food we eat.
I am sure that there are many other solipsists out there.
The issue you are missing here is that for some obese people, it's not excess storage, it's missallocated storage. They contract a virus that lives in and feeds on fat cells, so it encourages the person who has a healthy diet and who gets exercise to continue storing nutritional intake as more fat cells instead of as the muscle cells that they would have stored that nutrition as if they did not have the virus. That is what is being suggested by these studies.
This is also what is leading nutrition experts to question the portayal of obesity in and of itself as a health risk. It's just not the case that being over a certain weight means you are at risk for disease, it's an indicator that you will want to monitor certain things perhaps, but at the end of the day, skinny or fat, if you binge on sugar, you are at risk for diabetes.