CrossFit Calorie Restriction Article

CrossFit Calorie Restriction Diet and Longevity.

Crossfit calorie restriction . . . Maureen Dowd, the famous political columnist, predicts a dystopian future, with few survivors . . .

“The year is 2084, in the capital of the land formerly called North America . . . The Navy-Air Force game goes on, somehow, and there are annual CrossFit games on the Mall, led by flesh-eating Dark Seeker Paul Ryan, now 114 years old. CrossFit is still fighting the Department of Agriculture’s food pyramid, even though there’s no Department of Agriculture and no food.”

CrossFit HQ is currently advocating a fairly high protein diet.  But at the same time they recommend 30% of calories come from protein, 40% from carbohydrates and 30% from fat.  If you search for CrossFit calorie nutrition on the CrossFit website you will see that they also suggest that people look into calorie restriction to prolong life and preserve health.

Calorie restriction diet

A calorie restriction diet is a term used to describe a diet that is low in calories, but sufficient in nutrients.  The calorie restriction diet that is associated with life extension research is more tightly defined.   Laboratory animals (usually rats) are often kept on an ad libitum diet.  This means that food is available and the animal may eat whenever it feels like it.   A lab animal on a calorie restricted diet receives a percentage of what an average rat eats ad libitum.   For example, an animal may be fed 60% or 80% of an ad libitum diet.

Longevity and a Calorie Restriction Diet

Research using a number of different species shows that calorie restriction seems to prolong life.  Nematodes are remarkable in this respect.   Why animals on calorie restriction diets live longer is still uncertain.   Scientists continue to investigate the reasons.   Many believe that life extension is a reproductive strategy.  If times are bad a nematode (or other organism) may shift into low gear and  conserve resources in the hope that things will get better in the future.  If things get better the animal would then shift back into normal gear and get on with the business of reproduction.

Calorie restriction produces some interesting physiological and behavioral changes. In animals, calorie restriction

  • Increases activity levels (possibly because food seeking behavior increases)
  • Improves blood lipid profile
  • Results in fewer tumors
  • Improves memory and cognitive function (Ha!  I know exactly where to find that sunflower seed I hid last week!)

Short-term Calorie Restriction.

Short term calorie restriction produces a lot of the same effects.  This might be good.  Calorie restriction for life is probably unappealing to most.   Short term or intermittent calorie restriction also up-regulate certain biochemical pathways.  Or down-regulate others.  So far, it looks like short term calorie restriction does a number of interesting things:

  • Decreases inflammatory response (may help with healing and reduce coronary artery disease)
  • Increasing apoptosis (cell death) in tumors (Mukherjee et al. 2004)
  • Slowing growth of blood vessels (which slows tumor growth)
  • Lowering production of growth hormones (which would also slow tumor growth).

These things would extend life.  People who practice intermittent fasting tend to have lower risk of coronary artery disease and diabetes (Horne et al. 2008).  Maybe restricting calories sometimes might be a good idea.  Before surgery, for example.  People who fast before surgery seem to have fewer complications.

Calorie Restriction Diet and Longevity

Would calorie restriction extend life in humans?  That question has not been answered.  The idea that a person could permanently follow the kind of restrictive diet needed to to induce life-prolonging effects without sacrificing quality of life seems unlikely.  It also seems unlikely that, as CrossFit HQ maintains, a person could follow this type of diet and still have all the energy they need to live a healthy active life.    Once of the things observed in animals is that they appear to be “more energetic” than control animals on normal diets. However, it is possible that the “youthful  vigor” exhibited by animals on highly restrictive diets is not youthful vigor, but agitation, anxiety and restlessness.  These are the kinds of behaviors we expect in starving people.  Calorie restriction may be an adaptive change to stress.

Calorie restriction can have some undesirable side effects

  • Reduced Growth Hormone levels
  • Ovarian atrophy
  • Reduced Thyroid hormone levels
  • Loss of Muscle mass
  • Loss of Bone Mass

And some other probably unwanted effects as well:

  • Increased Aggression
  • Hoarding behavior
  • Voracious eating patterns
  • Throwing feces at researchers
  • Throwing whatever else you can get your little paws on at researchers

An important thing to keep in mind is that there is a difference between following an ad libitum diet when you are locked alone in a small cage with nothing but a pile of kibble and living a free life.    Animals in the wild live through good times and bad.  Having 20 – 40% less calories than you would eat if you were stuck in your room with a big bag of chips is a far cry from leading an active life.  Restricting calories in an otherwise free-living wild animal who works for a living may have very different effects.  Don’t be in a huge hurry to do this to your self.

A probably well-meaning lunatic  talked about putting his infant daughter on a calorie restriction diet so she would live a very long, healthy life.  (I must be a nut magnet.)  To all who are considering doing this to their children remember those news stories about kids found starving in locked closets.  The kids did not do well in there.   If you are considering doing it to yourself, understand that the point to reach is not starvation.  Calorie restriction may result in beneficial changes in physiology by causing mild stress.  That might mean just enough stress to increase activity levels, and alter physiology to produce some health benefits.  Huge food stress may not give the same results.  Huge stress in general has little going for it.


Robertson LT, & Mitchell JR (2013). Benefits of short-term dietary restriction in mammals. Experimental gerontology, 48 (10), 1043-8 PMID: 23376627

Mukherjee P, Abate LE, & Seyfried TN (2004). Antiangiogenic and proapoptotic effects of dietary restriction on experimental mouse and human brain tumors. Clinical cancer research : an official journal of the American Association for Cancer Research, 10 (16), 5622-9 PMID: 15328205

Submit a Comment