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Digging in: keto and intermittent fasting

Last Modified: March 13, 2019

Nutrition & Recipes

Throughout the month of March, we’re taking on some of the trending topics in the world of nutrition. In this post, Adrianne Kartholl, RDN, CD, clinical nutrition supervisor, and Elle Stronczek, RDN, CD, clinical dietitian, discuss the pros, cons and unknowns of the ketogenic diet and intermittent fasting.

Ketogenic diet

Our bodies are made to run off of glucose, which in its simplest form, is sugar, which we find in fruits and carbohydrates, like bread and pasta. With the ketogenic diet, people are training their bodies to use ketones, which come from fat sources, instead of glucose. That high fat diet allows the body to go into ketosis.

While today, we hear about the ketogenic diet as a means for weight loss, back in the 1920s, physicians began working with children who had epilepsy, to use ketones instead of glucose as fuel to control seizure activity. This approach is still used today. Some children can come completely off of their medications and control their condition through diet.

Those following the keto diet, aim to get over 50 percent of their calories from fat sources and 20-30 percent from carbohydrates. Their plates will be filled with items like cheese, avocado, fatty meats and oils, and less fruits and vegetables, pastas and breads.

There is a lot of supplementation that has to happen with someone practicing keto. The body isn’t getting the nutrients found in the foods they’ve cut out. The diet also isn’t intended to be followed forever. The children with seizure disorders are only meant to follow keto for 2-3 years before being coming off of the diet. If followed long term, people are at risk of deficiencies. Also, a high dietary fat intake can elevate cholesterol and put people at risk for heart issues. A final consideration is the tendency to gain the weight back. Once you return to eating carbohydrates, your body will revert back to your normal metabolism and you will likely see the weight come back, and possibly, some additional weight as well.  

Intermittent fasting

Intermittent fasting isn’t as restrictive regarding what you’re eating, but rather when. There are several options for intermittent fasting. Perhaps the least rigorous is fasting for 12 hours. Next would be fasting for 16 hours, and limiting the eating window to just 8 hours. Another approach is to eat normally for 5 days, and then on 2 nonconsecutive days, they fast to 500-600 calories for the day.

In animal research, intermittent fasting has shown to improve diabetes, blood lipids and blood pressure, control weight loss and improve appetite control. But it’s unknown if this applies to humans as well.

As far as which approach to intermittent fasting is best, there isn’t a lot of information to support one approach over the other. If you want to try it, consider starting with the least restrictive fasting schedule, 12/12.

The risks associated with intermittent fasting include becoming too preoccupied with fasting. Since there isn’t a lot of research, there could be harmful effects. Consider focusing on small, sustainable changes. If you’re planning to try anything substantial, consult with your primary care physician.


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