Saturday, June 27, 2009

Paleo Diet

I've been doing lots of reading on diet lately. I came to the Paleo Diet via two paths: my boss has successfully lost a good twenty kilos by adhering to it, and it's a logical extension of the grain-free diet I've been testing out.

What I like about the Paleo Diet is that it is not based on our rather hazy understanding of the biochemistry of the human body, but on our understanding of evolution. It's simple: for the vast bulk of the history of the human race (say 1 million years), we lived as hunter-gatherers. It is only in the last 10,000 years (if that) that we've had agriculture and have eaten the foods which that has provided. The Paleo Diet is based on the premise that our bodies have evolved to eat a hunter-gatherer diet, but not an agricultural diet. One can further surmise that the many "diseases of civilisation" may be rooted in the current dependence on a diet to which our bodies are not accustomed.

So, what did a hunter-gatherer diet look like? Apparently, they got about 45-65% (by energy) of their food from meat (indeed, the Inuit's complete diet consisted of meat). That is: hunted game, eggs, fish and insects (witchetty grubs and bogong moths!). The rest was plant food such as leaves and roots, and any fruit and nuts that were in season. Obviously the exact food varied from region to region, and from season to season. What was notably absent was food high in carbohydrates, such as grains, legumes and potatoes.

By comparison, the modern diet is overly dependent on high-carb foods and sugar. Obesity and diabetes are an obvious result of that. I'm not sure of the mechanism, but high-carb, low-fat diets seem be bad for heart disease.

Mark Sisson provides an overview of how much carbohydrate we should eat. The typical modern diet consists of about 150-300g of carbohydrate per day, with the upper end leading to rapid weight gain and disease risk. He suggests aiming for 100-150g of carbohydrate per day on a Paleo Diet. Going for less makes it easy to lose weight, particularly under 50g/day (where your metabolism starts doing some interesting things!).

So how much protein? Mark Sisson suggests you aim for a minimum 0.5g/lb of lean body mass (i.e. your weight, minus the fat), and 0.7/g to 0.8g/lb if you're are moderately active. So that's 1.1-1.7 g/kg of lean body mass. I weigh 68kg, and would guess my lean body mass was about 60kg, so I would need to aim for 65-100g of protein. Thanks to CFS, I'm not very active at all so the lower figure will do. Conventional wisdom says to aim for 0.8g/kg of body mass, so the Paleo Diet is hitting the protein a fair bit harder.

The energy balance comes from fat - and it needn't be polyunsaturated fat. Saturated fat is fine, and omega-3 fats are best. I'll write more on fats later.

Next post, I'll do breakdown my typical daily diet and work out what I need to change to go Paleo.

2 comments:

  1. Hey G,

    So the thing with diabtes is that you have way too much sugar floating around in your bloodstream because it doesn'y get taken up into peripheral cell (it still can enter brain cells) because of the demise of insulin-dependent glucose transporters. Then, all the glucose, having nowhere to go like a bunch of teenagers, binds to the vessel walls and damages them, by making them all hard and dysfunctional. This especially bad in the really really small vessels in your eyes (retinopathy), feet, and kidneys. Then you have poor blood flow and then everything goes bad.

    Now, the high fats and cholesterol also float around in the bloodstream, and if you have hardened, damaged vessel walls (from the hyperglycaemia), the fats (in the form of low-density lipoproteins/LDLs) infiltrate into the walls and deposit underneath. Cheeky buggers. They accumulate there and causing narrowing of the vessel from within.

    Then, with the damaged, narrowed, fatty vessel walls, the person usually also has high blood pressure. THis is because the narrowed walls have a smaller radius, and this increases pressure as the blood volume is constant.

    So the high pressure crashes against these damaged walls, that sort of crack and start to bleed, and then the clotting system gets activated and the whole intra-luminal space becomes clogged with a clot and you get angina, (decreased blood flow to the heart muscles via coronary arteries) and 'heart attack'. If the clot breaks up a bit, it can shoot off other chunks (embolism) up to the brain and cause a stroke.

    So, that's why hyperglycaemia/diabetes, high-fat diet, + hypertension causes heart and vascular disease.

    But, also, in high carb diets, excess glucose gets stored as fat/lipid, converted by the liver, and then transported to adipose/fatty tissue packaged as these LDLs can also infiltrate into damaged vessels.

    So, you're damned if you do, damned if you don't.

    Nic G

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  2. Hey Nic,

    Great run-down of the process!

    From what I've been reading, I don't think the fat aspect of it is that simple. There appears to be small LDL and large LDL (as in the size of the cholesterol particles). Small LDLs are the real killer, because they are the ones to get lodged in the arteries. So where do small LDLs come from? From carbs - particularly wheat, sugar and cornstarch. I'm not sure what the mechanism is, though.

    Have a read of this:
    http://heartscanblog.blogspot.com/2009/03/cholesterol-effects-of-carbohydrates.html

    If you scan through his blog you will see all sorts of stuff about this. Very interesting!

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