Saturday, Sep 17, 2011
When you replace the carbohydrates you eat with fat, you're creating a radical shift in the fuel that your cells will burn for energy. They go from running primarily on carbohydrates (glucose) to running on fat-- both your body fat and the fat in your diet.
As mentioned in passing earlier, insulin signals our kidneys to reabsorb sodium, which in turn causes water retention and raises blood pressure. When insulin levels drop, as they do when we restrict carbohydrates, our kidneys will excrete the sodium they've been retaining and with it water. For most people this is beneficial, and it's the reason why blood pressure comes down with carbohydrate restriction. For some individuals, though, the body will perceive the water loss as something to be prevented. It does so through a web of compensatory responses that can lead to water retention and what are called electrolyte imbalances (the kidneys excrete potassium to save sodium), and the results are [the potential side effects of weakness, fatigue, nausea, dehydration, diarrhea, constipation and dizziness when standing up quickly]. The reaction can be countered by adding sodium back into the diet: taking a gram or two of sodium a day (a half to one teaspoon of salt) or drinking a couple of cups of chicken or beef broth daily.
If you happen to be diabetic or hypertensive, then a doctor's guidance is critical. Since restricting carbohydrates will lower both blood sugar and blood pressure, if you're already taking drugs to do the same, the combination can be dangerous. Abnormally low blood sugar (known as hypoglycemia) can cause seizures, unconsciousness, and even death. Abnormally low blood pressure (hypotension) can induce dizziness, fainting, and seizures.
The potential side effects of carbohydrate withdrawal confuse the short-term effects with the long-term benefits of overcoming that withdrawal. The more technical term for carbohydrate withdrawal is keto-adaptation, because the body is adapting to the state of ketosis that results from eating fewer carbohydrates. These symptoms have nothing to do with the high fat content of the diet. Rather, they appear to be a consequence of either eating too much protein and too little fat, of attempting strenuous exercise without taking the time to adapt to the diet, or, in most cases, of the body's failure to compensate fully for the restriction of carbohydrates and the dramatic lowering of insulin levels that ensue... It's like telling smokers who are trying to quit that their withdrawal symptoms are caused by a 'need for cigarettes' and then suggesting they go back to smoking to solve the problem.
Why We Get Fat, Gary Taubes, 2010, http://www.amazon.com/Why-We-Get-Fat-About/dp/0307272702.