Low energy levels
Carbohydrates are the body`s preferred fuel when they are available (see chapter 4). As well, they burn more efficiently than fats. Many individuals voice concerns about drops in general energy levels (not including exercise) on a ketogenic diet due to the lack of carbohydrates.
Many subjects in early studies on ketosis or the PSMF noted transient lethargy and weakness. As well many studies noted a high occurrence of orthostatic hypotension which is a drop in blood pressure when individuals move from a sitting to standing position. This caused lightheadedness in many individuals. It was always taken for granted that ketosis caused this to happen.
However, later studies established that most of these symptoms could be avoided by providing enough supplemental minerals, especially sodium. Providing 4-5 grams of sodium per day (not much higher than the average American diet) prevents the majority of symptoms of weakness and low energy, possibly by maintaining normal blood pressure (26).
In most individuals fatigue should disappear within a few days to a few weeks at most. If fatigue remains after this time period, small amounts of carbohydrates can be added to the diet, as long as ketosis is maintained, or the diet should be abandoned for a more balanced diet.
The effects of ketogenic diets on exercise are discussed in chapter 22. To summarize, ketogenic diets can generally sustain low-intensity aerobic exercise without problem after a period of adaptation. However because carbohydrates are an absolute requirement to sustain high intensity exercise such as weight training or high-intensity aerobic exercise, a standard ketogenic diet is not appropriate.
Electrolyte excretion/Death
The diuretic (dehydrating) nature of ketosis causes an excretion of three of the body`s primary electrolytes: sodium, potassium, and magnesium (31,40). These three minerals are involved in many processes in the body, one of which is the regulation of muscle contraction, including the heart. Some studies show a net loss of calcium while others do not (31).
A severe loss of electrolytes is problematic. At the least, it can cause muscle cramping, which is often reported by individuals on a ketogenic diet. At the extreme, it can compromise normal heart function.
During the late 1970`s, a large number of deaths occurred in individuals following a 300 calorie per day liquid ketogenic diet called "The Last Chance Diet" (41-43). This diet relied on a processed protein as its only source of calories and the protein, which was a hydrolyzed collagen protein with the amino acid tryptophan added to it, contained no vitamins or minerals. As well, mineral supplements were not given or suggested to individuals on the diet.
Several possible causes for these deaths have been suggested, including the direct breakdown of the heart due to the low quality of protein used (42). A second, and more likely cause was that the depletion of electrolytes caused fatal heart arrhythmias. As well, given high quality protein and adequate mineral supplementation, no cardiac abnormalities appear in individuals on a ketogenic diet (44).
"The Last Chance Diet" should be contrasted to a ketogenic diet based around whole foods. The intake of whole protein foods will ensure some intake of the three electrolytes. Even so, studies show that the amount of electrolytes consumed by most on a ketogenic diet is insufficient. Some of the fatigue which was demonstrated in early ketogenic diet studies may have occurred from insufficient mineral intake, especially sodium (26).
A known effect of ketogenic diets is a decrease in blood pressure, most likely due to sodium excretion and water loss. In individuals with high blood pressure (hypertension), this may be beneficial. Individuals with normal blood pressure may suffer from 'orthostatic hypotension' which is lightheadedness which occurs when moving from a sitting to standing posture (45). The inclusion of sufficient minerals appears to be able to prevent symptoms of fatigue, nausea and hypotension (26).
Zitat von Angulus
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