Tuesday, August 3, 2010

Calorie restriction

You probably have never heard of Clive McCay and this brief article is not about dieting. As we have discussed before, it is easy to over-eat due, in part, to an abundance of food and encouraging genetics. Calorie restriction is what every (yes, every) weight loss diet promotes, but what of calorie restriction in the lean?

Fewer calories, longer lifespan

It was 1935 when Clive McCay wrote the first paper detailing an increased life span when food was restricted, as opposed to animals that had ad libitum feeding. Subsequent research suggested that restricting energy (calories/kilojoules) alone was the cause of an extended life, providing that all the essential nutrients were provided. Energy restricted laboratory animals were living about 20% longer than animals eating whenever they liked.

Fewer calories, less cancer

Even as early as 1942 it was noticed that energy restricted animals also had less spontaneous tumours leading one researcher to say: “__It follows that the avoidance of overweight through restriction of food intake may aid in the prevention of human cancer or at least delay its onset.__” That idea was a whole lot more likely in 1942 compared to around-the-clock eating in 2010. The idea still has merit as overweight people are more prone to cancer than lean folk.

More fasting, fewer calories

A 1946 paper acknowledged that natural energy restriction would be difficult in humans as they have a strong in-built desire to eat. They found that rats that were occasionally energy restricted by being fasted 2-3 days a week also had an extended lifespan and less tumours.

With humans long fascination with looking and feeling young, there have more recently been human studies on energy restriction. Like other animals, it seems that less food means better health and a longer life, although the effectiveness in humans is not yet definite due to our relatively long lifespan (lab rats live for 3 years; many humans clock up 85 years so you would have to track humans for 100 years before you might have the definitive answer).

What does it all mean?

If you are happy to under-eat once you reach adulthood, then there is a reasonable chance that you will live longer than normal. It will mean no chocolate, cabernet sauvignon, brie, premium ice cream and many other flavoursome foods. I would struggle there. It will also mean being active all your life. Happy with that angle.

The reality is that two-thirds of the population in a western country over-eat and hope that pills, crack-pot diets and surgery will conquer the excess. Energy restriction in western countries doesn’t appear to be achievable. Energy restriction, like human rights, world peace and the French football team, looks good on paper.

Reference: Journal of Nutrition. 2010 (July); 140: 1205-1210

1 comment:

smentha said...
