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Cut Calories, Boost Longevity?
April 4, 2006 -- Trimming calories may affect certain markers of longevity, but it's not clear if that means living longer.
The news comes from a study in The Journal of the American Medical Association. The study included 48 overweight people in Baton Rouge, La.
Participants were split into four groups, three of which had their calories curbed to varying extents. Six months later, the dieters showed several changes in markers of longevity.
The study was too short to check life span effects. Restricting calories has been tied to longevity in rodents and other short-lived species. But it's not clear if that's also true for people, write the researchers.
They included Leonie Heilbronn, PhD, and Eric Ravussin, PhD. Heilbronn worked on the study at Louisiana State University's Pennington Biomedical Research Center, where Ravussin is a professor. Heilbronn now works at the Garvan Institute for Medical Research in Darlinghurst, Australia.
Preliminary Data
"I think it's exciting data," Ravussin tells WebMD, cautioning that he and his colleagues didn't prove that cutting calories lengthens life.
The study tracked "biomarkers of aging," Ravussin says, including blood sugar (glucose) levels, insulin (a hormone that controls blood sugar) levels, and core body temperature. The results showed fasting insulin levels, body temperature, DNA damage, and metabolism were lowered with calorie restriction.
"Those are preliminary data suggesting indeed calorie restriction in nonobese people can potentially extend life span in people," Ravussin says.
He adds the study was "way too short" and had "way too few subjects." The next step is to do a similar study lasting at least two years to get "a little bit more definitive answers," Ravussin says.
Going Low-Cal
First, Ravussin and colleagues checked participants' metabolism, core body temperature, DNA damage, and fasting insulin levels. Next, they split participants into four groups:
- Comparison group: No changes in daily calories
- Calorie restriction group: Calories cut by 25%
- Calorie restriction plus exercise group: Calories cut by 12.5%, calories burned in exercise raised by 12.5%
- Very low calorie group: Calories cut to 890 daily calories until 15% of body weight lost, followed by weight-maintenance diet
Participants were in their mid- to late 30s, on average. Their average BMI (body mass index) at the study's start was about 27, which is overweight but not obese.
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