Journalistic malpractice

A recent Associated Press article demonstrates how the news media often miscover medical and scientific news.

The title and first paragraph of the article sound promising:

Study: Even mid-life diet change can extend life

WASHINGTON (AP) — It has long been known that laboratory animals live longer on a low-calorie diet. Now a study suggests that even if sensible eating is delayed until middle age, health can be improved and life extended.

 
And with childhood and adult obesity a serious problem in the United States, who wouldn’t find these paragraphs reassuring?

The carry-home message from the study, said Linda Partridge of University College London is that it is never too late to improve health by switching to sensible eating habits.

“If this works in humans, then it means that from the time a person starts on a restricted diet, they’ll be like individuals of the same age who were always on that diet,” she said. “Their prospects of survival are the same.”

 
That reassurance fades, though, if you read to the end of the article:

James R. Carey, a University of California, Davis, researcher who studies the biology of aging, said the Partridge study is “important to the field,” but does not provide final answers about the true effects of restricted diets.

He said that fruit flies and other animals on restricted diets tend to stop reproducing. In mammals, for instance, the females stop ovulating and, hence, cannot reproduce.

As a result, Carey said, animals on restricted diets may live longer simply because they are not expending energy and stress in the rigors of reproduction. He said studies still need to specifically isolate and prove that it is the lean diet alone that leads to longer life, and not related factors.

 
If we can extrapolate from an experiment on fruit flies that a restricted diet can improve health and extend life for people, then can we not also extrapolate that a restricted diet will lead to infertility as well?

I don’t understand why the Associated Press chose to run a story as weak as this one (and such weak stories are not uncommon on scientific and medical topics). Why waste the reader’s time and hope — why risk misleading the reader — with speculation disguised as medical advice? What’s wrong with waiting for better evidence?

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