Some Thoughts On Calorie Restriction (CR)
Calorie Restriction (CR) is getting a great deal of media attention due to studies that find animals raised on restricted calories live longer and suffer from fewer diseases. That advice may seem counter to the “bodybuilding/fitness lifestyle” we all follow.
Sure, we all know excess calories—minus any exercise to counter those additional calories—represent a negative for general health and longevity, but should people be severely limiting their calories?
As many of you know, studies have suggested that lower calorie intake translates into longer life spans in animals and—perhaps—people. However, this conclusion is controversial and far from conclusive in my view. For example, a recent study suggests that fat mass, not calorie intake, is what is responsible for longer life spans, at least in mice. (1)
And what does the bodybuilding lifestyle strive for? More muscle and less body fat! Remember, as one would expect, caloric intake and low body fat (leanness) are directly interrelated, which makes it difficult to determine the relative importance of each (CR vs. bodyfat levels) and their contributions to longevity. Thus, researchers are now trying to separate the two issues.
Recently, a Dr. Kahn and colleagues from Harvard Medical School created a strain of mice that lack insulin receptors in their fat cells. As insulin is a primary hormonal mediator of body fat levels in response to caloric intakes, this lack of insulin receptors in the animals’ fat cells caused the mice to have reduced fat mass (less body fat)—and also protected them from age-related problems, such as obesity. However, their calorie intake remained normal and no restriction was required to get the effect that would normally be seen with CR!
The researchers found that the experimental mice lacking insulin receptors in their fat cells had an approximately 18% increase in mean lifespan over their non-modified red eyed squeaky counterparts.
Studies like this one are helping to sort out the effects of leanness (body fat levels) and CR, and their respective effects on longevity and—perhaps—disease prevention. As we can’t all have our insulin receptors removed from our fat cells, researchers are looking to develop drugs to reduce—or block—insulin action in fat cells in humans.
Although such drugs could potentially have side effects, they may also be able to prevent obesity, type 2 diabetes and metabolic diseases related to body fat and excess calories, without having to use strict CR. Hey, we might even live longer!
Bottom line here is, I would not leap onto the CR bandwagon just yet, but would attempt to keep my body fat level low and under control via good nutrition and the bodybuilding lifestyle.
People who allow themselves to get fat (“Dude, I am off season!”) may not be optimizing their longevity, but heck, the guy who actually invented the theory of CR and longevity—Dr. Roy Walford—who practiced CR, died at the very average age of 79, so take that for what it’s worth…
(1) J. Science 2003;299:572-574.