The Truth about Fat

March 24, 2012 § Leave a comment

Surgeon Gabriel Weston claims that we are in the middle of a fat epidemic. In this week’s Horizon documentary she seeks to explain a “mystery”, why she asks when we are all surrounded with ample food do some people pile on the pounds while others do not?

Weston’s documentary makes an appropriate companion piece to last week’s The Truth about Exercise. The focus this week is on appetite and individual differences. Weston tells us that there is a hunger hormone (Ghrelin) and a fullness hormone (PYY). Dr Carel Le Roux says that the gut talks to the brain and influences how hungry or full we feel.

Using a functional MRI scan Weston’s brain is shown to be normal, with limited activation in response to calorie-rich food. By comparison a scan of an obese person’s brain reveals considerable activation in areas of the brain associated with “reward-centres”, addiction and emotional responses to food. Psychiatrist Dr Samantha Scholtz says that gastric bypass surgery can change the way the brain responds to food. 21 stone Marylin Walsh underwent a stomach bypass operation at Dr Le Roux’s hospital; within weeks she had lost four stones. More interestingly she reports that she no longer desires sweet or fatty foods. Weston is shown before and after brain scans of an obese person who had a stomach bypass and while the before image demonstrated great activity in response to high calorie foods, the post-operation scan shows minimal activity just like Weston’s own scan.

Discussion

The Truth about Fat is an interesting documentary but while I found Gabriel Weston’s narrative compelling I kept wondering if there were alternative explanations that were not offered. I felt that time given over to dissections of pigs to show us visceral fat might have been better dedicated to providing stronger evidence to support the theories advanced.

At the start of the programme  Weston explains that the human brain evolved at a time when food was scarce and therefore is attuned to storing energy, however in today’s world with plentiful food available 24/7, behaviour that was once useful to human survival is maladjusted to modern life. An interesting theory, but why I wondered has the fat epidemic that Weston talks about only taken hold (outside of the US) in the last 2o years when for most of the 20th century food has been cheaper and more plentiful than any other time in our history. While I find Weston’s explanations quite persuasive I felt she need to go a little further to make her case completely convincing.

Another example is the former shot putter who tells us that despite being very motivated he found it impossible to increase his weight beyond a certain point. This is an interesting change of tack from the usual case studies of people trying to lose weight; however this was only one person and therefor it is impossible to say whether this individual is a one-off or representative of the wider population.

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