Veggies are a staple of a calorie restricted diet.

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Is Calorie Restriction the Future?

Scientists believe that by consuming significantly fewer calories, you could increase your lifespan by about four or five years [source: Britt]. Though a few extra years might not seem impressive considering how much longer, percentage-wise, the lab mice lived, it's worth considering that there may be some additional health benefits. In some studies, caloric restriction has been shown to lower blood pressure, improve heart health and boost the immune system in people. Some people also demonstrated lower body temperatures and lower insulin levels, which are believed to be tied to longevity [source: Mason].

That's the problem with longevity research and caloric restriction: Scientists have many beliefs and theories on how to measure results, but they aren't exactly sure what they're looking for. We're not even sure exactly how calorie restriction works. There are two basic schools of thought, one being that calorie restriction works because the stress of starving shifts the body into a self-preservation response that helps it survive longer on less. Others believe that by simply putting less into our body, certain systems don't have to work as hard, thus experiencing less wear and tear. But getting any more specific involves different hypotheses about whether genes, hormones, free radicals or cell divisions make the ultimate difference.

Even those trusty lab creatures are no help on sorting it all out, and many studies only demonstrate how little we know about this diet. Calorie restriction extends life in fruit flies, but not houseflies [source: Wanjek]. It benefits fat mice, but not already-lean mice, and calorie restriction works for mice that were bred specifically for laboratory studies, but not mice found in the wild [sources: Britt, Wanjek]. When the caloric restriction is too extreme, at 60 percent reduction, the mice starve to death [source: Wanjek].

This diet would stunt children's growth, but scientists aren't sure when a person should begin calorie restriction to obtain the maximum benefit. Calorie restriction also wouldn't be prudent for the elderly or the ill, and even perfectly healthy folks may not be able to sustain such a sparse diet. There are, of course, some side effects to eating less, including loss of libido, cessation of menstrual periods, loss of memory and muscle mass, and dizziness. You may look gaunt or emaciated, and there can be other weird cosmetic effects -- a New York magazine article featured a man who had orange hands from consuming so many carotenoids [source: Dibbell].

Those interested in calorie restriction are urged to consult a doctor before beginning, though don't be surprised if you're met with disdain. Many simply don't believe this extreme diet is feasible, which is why some researchers focus on finding a pill that could mimic the effects of caloric restriction. Until then, consider this: Will it be fun to live forever if you can't order popcorn at the movies, travel to Italy for a heaping bowl of pasta or have a slice of cake at a loved one's wedding?