First, let’s talk about ketogenic diets, which require reduction of digestible carbohydrates to 50 grams a day or less for most folks. The iconic ketogenic diet is the induction phase of the Atkins diet, which restricts carbs to a max of 20 g daily. Note that the average American eats 250 to 300 grams of carb daily.
Your body gets nearly all its energy either from fats, or from carbohydrates like glucose and glycogen. In people eating normally, 60% of their energy at rest comes from fats. In a ketogenic diet, the carbohydrate content of the diet is so low that the body has to break down even more of its fat to supply energy needed by most tissues. Fat breakdown generates ketone bodies in the bloodstream. Hence, “ketogenic diet.” Also called “very-low-carb diets,” ketogenic diets have been around for over a hundred years.
WHAT COULD GO WRONG EARLY ON?
Very-low-carb ketogenic diets have been associated with headaches, bad breath, easy bruising, nausea, fatigue, aching, muscle cramps, constipation, gout attacks, and dizziness, among other symptoms. “Induction flu” may occur around days two through five, consisting of achiness, easy fatigue, and low energy. It clears up after a few days.
Other effects that you might not even notice immediately (if ever) are low blood pressure, high uric acid in the blood, excessive loss of sodium and potassium in the urine, worsening of kidney disease, deficiency of calcium and vitamins A, B, C, and D, among other adverse effects.
A well-designed ketogenic diet should address all these potential issues. My Ketogenic Mediterranean Diet is an example. I followed it for for six months and blogged about it. (The KMD is not a paleo diet.)
Athletic individuals who perform vigorous exercise should expect a deterioration in performance levels during the first three to four weeks of any ketogenic very-low-carb diet. The body needs that time to adjust to burning mostly fat for fuel rather than carbohydrate.
Competitive weight-lifters or other anaerobic athletes (e.g., sprinters) will be hampered by the low muscle glycogen stores that accompany ketogenic diets. They need more carbohydrates.
WHAT ABOUT THE LONG RUN?
Long-term effects of a very-low-carb or ketogenic diet in most people are unclear—they may have better or worse overall health—we just don’t know for sure yet. Perhaps some people gain a clear benefit, while others—with different metabolisms and genetic make-up—are worse off.
If the diet results in major weight loss that lasts, we may see longer lifespan, less type 2 diabetes, less cancer, less heart disease, less high blood pressure, and fewer of the other obesity-related medical conditions.
Ketogenic diets are generally higher in protein, total fat, saturated fat, and cholesterol than some other diets. Some authorities are concerned this may increase the risk of coronary heart disease and stroke; the latest evidence indicates otherwise.
Some authorities worry that ketogenic diets have the potential to cause kidney stones, osteoporosis (thin, brittle bones), gout, deficiency of vitamins and minerals, and may worsen existing kidney disease. Others disagree.
It’s clear that compliance with very-low-carb diets is difficult to maintain for six to 12 months. Many folks can’t do it for more than a couple weeks. Potential long-term effects, therefore, haven’t come into play for most users. When used for weight loss, regain of lost weight is a problem (but regain is a major issue with all weight-loss programs). I anticipate that the majority of non-diabetics who try a ketogenic diet will stay on it for only one to six months. After that, more carbohydrates can be added to gain the potential long-term benefits of additional fruits and vegetables.
People with type 2 diabetes or prediabetes may be so pleased with the metabolic effects of a ketogenic diet that they’ll stay on it long-term.
Steve Parker, M.D.