Eating less may not extend life

Jan 23, 2009

If you are a mouse on the chubby side, then eating less may help you live longer.

For lean mice - and possibly for lean humans, the authors of a new study predict - the anti-aging strategy known as caloric restriction may be a pointless, frustrating and even dangerous exercise.

"Today there are a lot of very healthy people who look like skeletons because they bought into this," said Raj Sohal, professor at the University of Southern California's School of Pharmacy.

He and Michael Forster, of the University of North Texas Health Science Center, compared the life span and caloric intake of two genetically engineered strains of mice.

The "fat" strain, known as C57BL/6, roughly doubles in weight over its adult life. That strain benefited from caloric restriction, Sohal said.

The "lean" strain, DBA/2, does not become obese. Caloric restriction did not extend the life of these mice, confirming previous work by Forster and Sohal.

The results appeared online Jan. 13 in advance of print publication in the Journal of Nutrition.

"Our study questions the paradigm that caloric restriction is universally beneficial," Sohal said. "Contrary to what is widely believed, caloric restriction does not extend (the) life span of all strains of mice."

By measuring the animals' metabolic rate, Sohal and his colleagues came to a deceptively simple conclusion: Caloric restriction is only useful when, as in the case of the obese mice, an animal eats more than it can burn off.

"Your energy expenditure and your energy intake should be in balance," Sohal said. "It's as simple as that. And how do you know that? By gain or loss of weight.

"The whole thing is very commonsensical."

For humans of normal weight, Sohal strongly cautions against caloric restriction. In a 2003 study, he and Forster found that caloric restriction begun in older mice - both in DBA and leaner C57 individuals - actually shortened life span.

However, Sohal said that obese individuals are probably better off cutting calories than increasing their exercise to make up for overeating. Overly vigorous exercise can lead to injuries and long-term wear and tear.

In other words, it is better to skip the double cheeseburger than to turn up the treadmill after binging at Carl's Jr.

Sohal's study is not the first to question the allegedly universal benefits of caloric restriction. A study by Ross et al. published in Nature in 1976 ("Dietary practices and growth responses as predictors of longevity") found that caloric restriction works best in mice that gain weight rapidly in early adulthood, Sohal said.

Studies of caloric restriction in wild types of mouse strains have shown minimal life span extension, he added.

Next, the researchers want to understand why the obese mice have a lower metabolic rate that promotes weight gain.

Source: University of Southern California

Explore further: Can YouTube save your life?

add to favorites email to friend print save as pdf

Related Stories

Earthquakes over 5 magnitude shake Iceland volcano

4 hours ago

Two earthquakes measuring over 5 in magnitude—the biggest yet—have shaken Iceland's Bardarbunga volcano after the country issued an aviation red alert warning that an ash-emitting eruption may be imminent.

Airlines on alert as eruption begins in Iceland

18 hours ago

Iceland's Bardarbunga volcano burst forth with a small eruption Saturday under the ice of Europe's largest glacier, scientists said, prompting the country to close airspace over the area.

Two Galileo satellites lose their way

21 hours ago

Two European Galileo satellites launched as part of a navigation system designed to rival GPS have failed to locate their intended orbit, launch firm Arianespace said Saturday.

Recommended for you

Can YouTube save your life?

19 hours ago

Only a handful of CPR and basic life support (BLS) videos available on YouTube provide instructions which are consistent with recent health guidelines, according to a new study published in Emergency Medicine Australasia, the jo ...

Doctors frequently experience ethical dilemmas

19 hours ago

(HealthDay)—For physicians trying to balance various financial and time pressures, ethical dilemmas are common, according to an article published Aug. 7 in Medical Economics.

AMGA: Physician turnover still high in 2013

20 hours ago

(HealthDay)—For the second year running, physician turnover remains at the highest rate since 2005, according to a report published by the American Medical Group Association (AMGA).

Obese or overweight teens more likely to become smokers

20 hours ago

A study examining whether overweight or obese teens are at higher risk for substance abuse finds both good and bad news: weight status has no correlation with alcohol or marijuana use but is linked to regular ...

Taking preventive health care into community spaces

21 hours ago

A church. A city park. An office. These are not the typical settings for a medical checkup. But a new nationwide study by the UCLA Center for Health Policy Research shows that providing health services in ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

ryuuguu
not rated yet Jan 23, 2009
the article may be accurate but seems poorly argued. the quote ate the end
"Studies of caloric restriction in wild types of mouse strains have shown minimal life span extension, he added."
seems to show if you don't genetically engineer mice calorie restriction helps extend lifespan.