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Low-Calorie Diet May Lead to Longer Life
April 05, 2006
Study findings lend support to the theory that eating less, long known to prolong life in rats and mice, may do the same for people, by preventing heart disease, cancer, diabetes and other diseases, and by slowing aging.
Our Review Summary
This article reports on a study published in the Journal of the American Medical Association, “the first rigorous test of calorie restriction in people who are overweight but not obese.” The story states potential benefits of calorie restriction without providing adequate context for understanding what it would take to maintain adequate nutrition long-term. People were paid $7,000 to be in the study and all the food consumed in the study was provided to the participants to ensure adequate nutrition. The story didn't explore the long-term practical implications of that approach for the average American. The long-term effect of maintaining body weights in the range supported by calorie restriction has not yet been established. This is an important caveat before concluding that the evidence demonstrates that such limits in caloric intake are beneficial.
Click on Criteria for definitions.
The story mentions 'people experimenting on themselves', indicating the potential for anyone to self-impose calorie limitations on themselves. However, the article failed to explain that all the food consumed by the research subjects in the study was provided for them thus ensuring nutritional adequacy while restricting calories. That's beyond the reach of the average American. People were paid $7,000 to be in the study!
Everything has a cost. Yet the story gave no cost estimate for the costs associated with consumption of foods 'high in nutrients but low in calories.'
There isn't any discussion of how many Americans are overweight but not obese, so we can't judge the story unsatisfactory on this criterion. However, we are tempted to do so when the story states, without attribution or evidence to back it up: "The notion that going hungry could be the fountain of youth has captivated scientists and the public."
This article reported on the results of a randomized controlled trial comparing the outcomes from 4 groups. There is no framework provided to assess the magnitude of potential improvement. Presentation of the results follows the opinions of the authors of the study without critical examination of that interpretation.
This article does a good job of highlighting the weight regain that occurs when peoples' adherence to a dietary program that provides all the food ends. However, there was no mention of potential side-effects or harms of long-term calorie restriction such as decreased testosterone, muscle mass or bone density.
This is not a novel 'treatment' for the length of life, notwithstanding the quote from Dr. Hadley from the National Institute on Aging stating that "There's never been a study like this one". This research is actually one of three pilot projects; results of the other two were published in 2005. The story explains that this "is the subject of intense research, and some people have already begun trying it on their own." And it explains that there is no data in non-obese but overweight people.
The story didn't quantify the suggested benefits (decreased insulin level, decreased body temperature, drop in thyroid hormones, and decline in DNA damage) gained by the study participants. And the study didn't mention the parameters that failed to demonstrate change during the study (protein carbonyl, glucose, and dehydroepiandroestrone sulfate (DHEAS).
We can't judge if the story relied solely or largely on a news release.
The main expert quotes in the story came from people with a vested interest in showing positive results. Evan Hadley of the National Institute on Aging (source of funding for the study) called the results of this pilot study "striking". In addition, an estimate for the number of individuals currently engaging in calorie restriction appears to have been obtained from the president of the Calorie Restriction Society. While this study is one of three pilots studies for the feasibility of calorie restriction in humans, no comments from the other research groups was included.
The story is about calorie restriction in overweight but non-obese people. But no alternative treatment options are discussed.
Total Score: 2 of 9 Satisfactory
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