The Cooper Institute

Founded in 1970 by the "Father of Aerobics"
Kenneth H. Cooper MD, MPH


The Ketogenic Diet

Posted in
Eat better

Tuesday, Jan 02, 2018

What’s in a Name? “Ketogenic” Diets.

Here we go again…The Internet and the public are buzzing about the latest dietary fad, the Ketogenic Diet. However, this not a new diet at all!  It’s the same approach as the ‘Low Carbohydrate Diet,’ which is the same thing as the Atkins Diet of the 1970’s, and the South Beach Diet of the late 1990’s. Same diet, different name…

The recommendation for the Ketogenic Diet is that you should consume only about 5-10% of your daily calories from carbohydrate, 70% of your calories from fat, and the remainder (20-25%) from protein. By way of comparison, the dietary recommendations from the Institute of Medicine (IOM) are 45-65% of daily calories from carbohydrate, 20-35% from fat, and 10-35% from protein. Of note, the IOM recommendations are backed by groups like the American Heart Association, American Cancer Society, American Diabetes Association, Surgeon General’s Office, and the overwhelming majority of Registered Dietitians.

Because dietary carbohydrate is extremely limited on the Ketogenic Diet, the body cannot rely very much on carbohydrate as a fuel source for energy. As a result, the body relies more on fat as a fuel source, and also relies on protein to some extent. In order to reach the very low carbohydrate goal of the Ketogenic Diet, one must avoid grains, dairy, fruit, some vegetables, and legumes (beans and peas). This leaves the dieter with the only options of eggs, butter, meat, fish, poultry, salad, nuts, and oily salad dressings. Not much variety, is there?

No one disputes that the Ketogenic Diet causes initial rapid weight loss. It’s not unusual for people to lose 5-8 pounds during the first week. Let’s peel back the layers though.  First, if one is trying to lose weight, they should be striving to lose fat weight. The scale does not tell us what kind of weight we are losing. Our body is about 60% water by weight. Carbohydrate is stored in our body as a substance called glycogen, which is found mostly in muscle and liver cells. Each gram of glycogen we store is accompanied by two grams of water. When we restrict carbohydrate intake, glycogen levels are depleted, and we rapidly lose a lot of water weight via urination. This does not make us healthier, it does make us somewhat dehydrated.   

Most diet studies are short-term, lasting only weeks or months. The real issue that needs to be examined is short-term weight loss versus long-term weight control. The former is relatively easy to achieve, while the latter is extremely difficult. This is evidenced by the fact that nearly 70% of the U.S. population is currently overweight or obese. If the dozens of fad diets (including ketogenic diets) over the past few decades were effective for long-term weight control, then rates of overweight and obesity would likely be in the single digits.

The short-term studies on ketogenic diets have shown temporary improvements in important risk factors like HDL and LDL cholesterol levels, blood glucose, inflammatory markers, and waist circumference. However, any dietary approach that leads to weight loss will tend to show these same types of improvements. 

For most people, the perceived ‘pros’ of the Ketogenic Diet are outweighed by the following ‘cons.’ 

  • Lack of variety. So many foods are limited with this approach that you will likely soon tire of eating the same things over and over again.
  • Lack of fiber. Complex carbohydrates are the only source of dietary fiber. Since carbohydrate intake is very limited with the Ketogenic Diet, you will be consuming a very low fiber diet by default. Low fiber diets are strongly associated with an increased risk of constipation, hemorrhoids, type 2 diabetes, cardiovascular disease, and digestive cancers. Think about that for a moment (or two).
  • Lack of essential nutrients. Ketogenic diets are notoriously low in several essential nutrients including vitamins C and D, as well as some of the B vitamins. Calcium is also lacking. Many ketogenic enthusiasts remain blissfully unaware that complex carbohydrates contain hundreds of beneficial substances called phytochemicals; which are naturally occurring non-nutrients that help to prevent disease.
  • The weight loss from the ketogenic approach is typically temporary, not permanent. When you change your eating habits short-term, your weight will also change short-term. The goal should not be short-term weight loss, but rather long-term weight control.
  • Fatigue and irritability. A ketogenic diet increases the likelihood of hypoglycemia (low blood glucose levels). Headaches, fatigue, and irritability are just a few of the many unpleasant symptoms of hypoglycemia.
  • Inability to perform regular sustained exercise. We’ve known for decades that diet plus exercise is far more effective for long-term weight control than either one by itself. Carbohydrate is a major fuel source for muscles during exercise. When carbohydrate stores are low and/or hypoglycemia is present, it’s very difficult to exercise.  
I will gladly acknowledge the fact that ketogenic diets have been shown to be helpful in treating severe epilepsy, and that a few people will be able to sustain their weight loss using this approach. However, for the majority of the population, the cons significantly outweigh the pros. Any weight lost during the Ketogenic Diet will likely be found again when people resume their old eating habits.