I am a fan of low-carbohydrate eating, and my position is based on the science (showing it to be usually effective for weight loss and improvements in disease markers) and my experience with it in practice. However, not everyone shares my enthusiasm for this way of eating. Many people like to paint carbohydrate restriction as somehow dangerous. In quite-extreme carbohydrate restriction the body will generally turn to ketones (created from the metabolism of fat and/or protein) as a fuel source. This results is a state known as ‘ketosis’. I don’t generally recommend extreme carb restriction, but I don’t fear ketosis either. I see it as a natural response of the body to carbohydrate restriction.
All too often, I think ketosis is confused with ‘ketoacidosis’, which is a whole other story. Ketoacididosis occurs when there are severe metabolic disturbances such as when blood sugar levels run out of control in type 1 diabetics. It’s a serious situation, and potentially life-threatening but, as I say, is not the same as ‘ketosis’.
Ketones provide fuel for the body and brain, but some have questioned how well they do this compared to other fuel sources (such as glucose). I was therefore interested to read about a recent study in which a very low carbohydrate ‘ketogenic’ diet was tested in individuals with ‘mild cognitive impairment’ (reduced brain function associated with ageing but not severe enough to be classified as dementia) . Half of the group in this study were randomised to eat the ketogenic diet, the other half ate a diet rich in carbohydrate. The study lasted 6 weeks.
The researchers found that those eating the ketogenic diet, compared to the other group, saw significant improvement in their ‘verbal memory’ (memory of words and other abstractions involving language). Also, generally speaking, the higher their ketone levels, the better their verbal memory tended to be. The suggestion here is that ketones provide ready fuel for the brain, and may enhance ‘cognitive function’.
Aside from memory improvement, those in the ketogenic diet also saw significant benefits in terms of weight loss and waist circumference reduction, as well as reductions in fasting blood glucose and insulin levels. Taken as a whole, these results suggest that carbohydrate restriction sufficient to induce ketosis offers, in the short term at least, significant advantages for both body and brain.
1. Krikorian R, et al. Dietary ketosis enhances memory in mild cognitive impairment. Neurobiol Aging 2 December 2010 [epub ahead of print]