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Light blogging: Obesity and personal responsibility May 30, 2007

Posted by Johan in Behavioural Genetics.

While most societies have become increasingly acceptant of the idea that people are not strictly personally responsible for addictions such as alcoholism, or psychological conditions like anorexia nervosa, one condition where the blame remains firmly on the shoulders of the individual is obesity.

This is likely to change in the future, as more and more people become obese. At some point, this minority will become large enough to affect the public debate more than it has so far. But at present, the popular notion is that obesity is caused by excessive eating and poor exercise (which is strictly speaking true), and that everyone should be equally able to behave accordingly (which is improbable).

The video below is a good example.

In Swedish media, this story has been reported with the angle that the mother is feeding her daughter copious amounts of food, and now the nice doctors have taken the child away to control her eating in a way that the mother did not. The only write-up I’ve found in English is from some Croatian news site. Conveniently, it matches the Swedish write-up word for word, so the original story is most likely from Reuters or AP.

When I saw the video, my initial reaction was – “ah, so that’s that Prader-Willi syndrome looks like.” Prader-Willi is a genetic condition (see the page on OMIM) caused by a number of gene deletions on chromosome 15 of the paternal gene.

It would be relatively easy to understand Prader-Willi if it produced obesity by slowing metabolism, so that a normal intake of food caused obesity, or through movement disorders that make it difficult to get enough movement into your day. Instead, the chief characteristic of Prader-Willi is insatiable hunger. People with this condition live through their days as though they are starving. A quote from a case study illustrates the point:

[…] The worst problem, though, was her appetite. She ate everything she could and never seemed satisfied. At first her parents were so pleased to see her finally gaining weight that they gave her food whenever she asked for it. But after a while it was clear that she was becoming obese. A specialist diagnosed her condition and told her parents that they would have to strictly limit Carrie’s food intake. Because of her weak muscles and low metabolic rate, she needed only 1200 calories per day to maintain a normal weight. But Carrie was constantly looking for food. She would raid the refrigerator until her parents installed a lock on it and on the cabinets where they put food. They had to be careful of how the disposed of leftover food, vegetable peels, or meat trimmings because Carrie would raid the garbage can and eat them. (Carlson, 2007, p. 395)

I think a lot of people have a common-sense understanding of behaviour where automatic processes are biological or genetic and cannot be controlled, while controlled behaviours such as eating are necessarily controllable, and thus reflect the individual’s shortcomings in self control. Prader-Willi syndrom is a striking example of how wrong this dichotomy is. Individuals with this condition experience such a strong drive for food that they simply cannot control themselves.

While I have no idea if the girl in the video above has Prader-Willi, I think this is a far more likely explanations than some kind of force-feeding instigated by the mother (note how the child asks for popcorn at one point in the video). Much like how schizophrenia and autism used to be blamed on the parents before the genetic underpinnings became understood, parents of Prader-Willi face constant derogation every time they show their face in public, because the obvious interpretation is that they are over-feeding their child.

In a sense, it’s true that parents are responsible for their children. But as the case study I cited above shows, these parents face a task that is almost impossible. Apart from the sheer physical difficult in preventing all access to food in a modern society, it must be emotionally straining to be unable to give your child food even though they feel as though they are starving.

While the very existence of a large increase in obesity worldwide suggests environmental rather than genetic influences, it’s clear that modern-day access to food is something that people are able to cope with to different extents. In a way it’s ironic that the features of obesity – binge eating, pre-occupations with food – must have been adaptive at one point in our history. When access to food is not always guaranteed, those who are able to make the most of opportunities to eat, who show the greatest interest in locating food, and who are able to metabolise the food efficiently will be more successful.

Still, the same false dichotomy between uncontrollable biological factors and controllable behavioural factors are used by many obese individuals too. Obesity acceptance groups usually emphasise biological factors such as metabolism, perhaps because they realise that these factors are more likely to elicit sympathy. But as Prader-Willi shows, sheer appetite can have a genetic component also.

Carlson, N.R. (2007). The Physiology of Behavior. London: Pearson.

Prader-Willi Syndrome @ Wikipedia

Prader-Willi Syndrome @ Online Mendelian Inheritance In Man (OMIM)


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