This is a long, detailed post by the Jaminets, and not necessary for the average guy or gal to understand in order to be healthy on a paleo prescription. However, for those geeks wanting to delve into the workings of the human body, it's highly explanatory:
Brain and nerves typically consume about 480 calories per day of glucose. Ketones can displace up to perhaps 60% of this, but ketones do not diffuse well into cortical areas of the brain and the brain always requires some glucose.
After 3 days of fasting, when the brain’s glucose consumption has been roughly halved by ketosis and the rest of the body is conserving glucose, the body’s rate of glucose manufacture in liver and kidneys is about 600 calories per day. [1]
Two things to note:
When not fasting, the body’s glucose utilization is somewhat higher – say, 800 to 1000 calories per day for a sedentary person. Glucose needs are slightly reduced by some endogenous sources of glucose, such as from glycerol released from lipolysis of triglycerides or phospholipids. So the body’s net glucose needs are on the order of 600 to 800 calories per day.
http://livinlavidalowcarb.com/blog/paul-jaminets-response-to-the-critics-of-his-safe-starches-concept/11920
What's the bottom line? Nearly all the players in the low carb arena point out a break point at about 100 to 120 grams per day of carb consumption, because at this level, your body has to produce enough carbohydrate to fully meet your carb needs. That means you will not be giving your body an excess glucose problem to solve (assuming the ~120g is mostly "good" carbs!).
There are folks who need to eat fewer carbs to maintain health and weight loss, and I do well on less than 100g/day. For example, since January of 2007 when I weighed 225, I've sustained a 15 pound weight loss, which put my under 15% body fat, which is easily in a safe, functional range. In the last few months, I've reduced my weight by another 10 pounds, by combining intermittent fasting with carb restriction. I'm within about five pounds of matching my body weight as a 22 year old. That's nothing special, but doing that without counting or even considering caloric intake, or hunger, while eliminating a compulsive sweet tooth, and generating good numbers on every objective health measure, and competing at a reasonably high level in CrossFit, whilst working against a poor genetic back ground (as regards weight gain on the SAD), is an endorsement of a paleo oriented carb restriction - in my humble as ever opinion.
Brain and nerves typically consume about 480 calories per day of glucose. Ketones can displace up to perhaps 60% of this, but ketones do not diffuse well into cortical areas of the brain and the brain always requires some glucose.
After 3 days of fasting, when the brain’s glucose consumption has been roughly halved by ketosis and the rest of the body is conserving glucose, the body’s rate of glucose manufacture in liver and kidneys is about 600 calories per day. [1]
Two things to note:
- Even in fasting, peripheral utilization of glucose exceeds the brain’s.
- The fasting level of glucose utilization is likely to be suboptimal for health: fasting invokes glucose-and-protein-conservation measures which evolved to make us more likely to survive famine, but almost certainly have a cost in long-term health. (The logic is similar to Bruce Ames’s triage theory [2].)
When not fasting, the body’s glucose utilization is somewhat higher – say, 800 to 1000 calories per day for a sedentary person. Glucose needs are slightly reduced by some endogenous sources of glucose, such as from glycerol released from lipolysis of triglycerides or phospholipids. So the body’s net glucose needs are on the order of 600 to 800 calories per day.
http://livinlavidalowcarb.com/blog/paul-jaminets-response-to-the-critics-of-his-safe-starches-concept/11920
What's the bottom line? Nearly all the players in the low carb arena point out a break point at about 100 to 120 grams per day of carb consumption, because at this level, your body has to produce enough carbohydrate to fully meet your carb needs. That means you will not be giving your body an excess glucose problem to solve (assuming the ~120g is mostly "good" carbs!).
There are folks who need to eat fewer carbs to maintain health and weight loss, and I do well on less than 100g/day. For example, since January of 2007 when I weighed 225, I've sustained a 15 pound weight loss, which put my under 15% body fat, which is easily in a safe, functional range. In the last few months, I've reduced my weight by another 10 pounds, by combining intermittent fasting with carb restriction. I'm within about five pounds of matching my body weight as a 22 year old. That's nothing special, but doing that without counting or even considering caloric intake, or hunger, while eliminating a compulsive sweet tooth, and generating good numbers on every objective health measure, and competing at a reasonably high level in CrossFit, whilst working against a poor genetic back ground (as regards weight gain on the SAD), is an endorsement of a paleo oriented carb restriction - in my humble as ever opinion.
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