Tuesday, July 20, 2010

What is in control of your appetite 2

In an earlier blog I mentioned that there is an internal drive to eat, grow and reproduce and this seems to over-ride the decision to eat well for a long life. We tend to over-eat to contend with famines although most of us haven’t experienced a food shortage since television.

Protein is life

We know how much protein is needed for growth and maintenance yet nearly all of us eat more than we need and actively seek high protein foods. In the US 97%, and in Australia over 90%, of the population eat more protein than needed (around 0.8g/kg day). As countries “develop” they tend towards an increase in protein intake. We love big steaks, seafood platters and, of course, triple bacon, double cheese, egg, thin slice of tomato for colour, megaproteinburgers.

A theory is that a high protein diet brings forward the onset of puberty and so extending the period of fertility. In affluent western societies the onset of women’s menarche is 11 years, while in rural China it is 17 years.

Protein is death

The bad news is that the desire to track down protein is linked to a shorter life. A moderate protein, calorie-restricted diet increases the lifespan of laboratory animals by around 20% compared to high protein diets. On the other hand (and I’m so glad we have two hands because there are so many on-the-other-hand situations in life) high protein foods are more satisfying than high carbohydrate foods so people are more likely to stop eating before they get too podgy. In theory.

Health campaigns ignore genes

We love food. Nature designed us that way. We love calorie-dense foods with plenty of protein and fat (hamburgers), and protein, fat and sugar (chocolate). The authors of this paper argue that our in-built tendencies are usually ignored in health campaigns and scientific study. For example, a campaign urging us to eat low calorie fruit and vegetables doesn’t make sense to our genetic desire for calorie-dense foods.

What does it all mean?

We were never designed for a long life, just a life long enough to get our children to reproductive age, so four decades is about all that is expected. And millions eat like they are happy with four decades before they clutch their chest and hit the floor. Dietary advice today runs counter to our natural instincts to eat foods that give us both pleasure and calories/kilojoules to reach a reproductive age.

Living to the age of 80 years is a relatively new experience for humans. Before the industrial revolution, 40-50 years was about all you could expect unless you were gentry. Go back 1000 years and you were looking at 30-35 years to be labeled “old”. For those us who are aiming to clock up eight or ten decades then eat like you want to live to 100, and live like you might die tomorrow. Just know, it won’t be easy.

Reference: Appetite. 2010; 54: 442-449

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