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Tue, 01 Sep 2009

Study Does Not Show that Fat People Are Brain-Damaged

A recent study published in the journal Human Brain Mapping [1] suggests that obesity and overweight are statistically linked to brain degeneration in elderly people. The LiveScience news website reported these results in a way that suggests that all obese people have brain damage [2]. The LiveScience article's title, "Obese People Have 'Severe Brain Degeneration'," is enough to create this misunderstanding. Other news outlets, such as [3], have reported the same story in a similar manner.


The study does NOT prove that fat people are brain damaged.

The study does not even show that being fat causes brain degeneration in the elderly.

The study suggests there is a statistical correlation between a high body mass index (BMI) and certain kinds of brain deterioration in elderly people. This is not the same as saying that being fat causes anything. One part of the original journal paper suggests that high BMI is not likely to be the actual cause of the observed brain changes, and that something else might be causing both the high BMI and the brain changes ([1], p. 9).

Misinformation about this study is a serious matter. If the media present this study the wrong way, people might take it to mean that all fat people are brain-damaged. This misunderstanding is sure to increase the widespread hatred of fat people, and to worsen the abuse of fat children, who often suffer vicious bullying, teasing, and social rejection because of their size. Even though the study involved elderly people and not children, the idea that being fat causes brain damage plays right into the "fat kids are stupid" stereotype, which already causes great harm to children who are genetically heavier than average.

There are at least two possible ways to explain the study's results without assuming that fat causes brain damage.

One explanation, which the paper already mentions, is that something could be causing both the high BMI and the brain changes. The paper mentions "reduced exercise" as one such possible cause ([1], p. 9). If this were the real cause, then fat people who get enough exercise should be able to avoid the brain problems. (Despite the widespread belief that fat people don't exercise, in reality many fat people do exercise - and some remain fat even when they are exercising a lot. [4])

Another possible explanation is that social stress and isolation are causing the brain problems. Fat people experience serious discrimination in our society, and this discrimination can affect health. (See reference [5] for relevant information.) Few thin people can fully imagine how much teasing, bullying, loneliness, and employment discrimination many fat people go through. It's no secret that social stress has bad effects on physical and mental health. Maybe some fat people develop brain problems because of a lifetime of social stress. If this is the explanation, then discrimination, not fat, is the cause of the brain problems. We can address this cause by working to end the discrimination.


Aside from the misleading media coverage, the study itself contains a feature that can be called into question. This is the study's use of BMI as an indicator of overweight and obesity. Although it is common to use BMI this way, BMI does not appear to be a very good measure of fatness or of poor health. (See references [5], [6] and [7] below for relevant information.)

Any scientific study is subject to future criticism by other scientists; results sometimes fade in the light of further studies. However, even if this study withstands the test of time, it does not show that fat people in general are brain-damaged.

These same warnings apply to any study that suggests that fat people of any age have brain problems. Studies of this sort do not automatically show that fat causes brain damage, or that fat people are stupid. The cautionary remarks given here might well carry over to other studies also.



[1] Cyrus A. Raji, April J. Ho, Neelroop N. Parikshak, James T. Becker, Oscar L. Lopez, Lewis H. Kuller, Xue Hua, Alex D. Leow, Arthur W. Toga, and Paul M. Thompson. "Brain Structure and Obesity". Human Brain Mapping (2009). Published online in Wiley InterScience ( DOI: 10.1002/hbm.20870. Accessed 8/25/2009.

[2] "Obese People Have 'Severe Brain Degeneration'". ( Posted 8/25/2009. Accessed 8/29/2009.

[3] "Study: Obese People Have 'Severe Brain Degeneration'". (,2933,542480,00.html) Posted 8/25/2009. Accessed 8/29/2009.

[4] For relevant information, see the following article on a U.S. government website: Marcia Wood, "Health At Every Size: New Hope for Obese Americans?" ( Published in Agricultural Research magazine, 3/2006. Accessed 8/29/2009. See also The Obesity Myth (reference [5] below).

[5] Paul Campos, The Obesity Myth (New York: Gotham Books, 2004).

[6] Raj Jayadev. "Muscle vs. Fitness". Metroactive. From Metro (newspaper), December 1-7, 2004. ( Accessed 8/29/2009.

[7] "Science of HAES". ( Accessed 8/29/2009. Includes articles by Dr. Paul Ernsberger.

posted at: 11:30 | path: /political | persistent link to this entry


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