by Katie Mark
If you could tap into your approximately 40,000 calories of stored fat during endurance exercise instead of relying on your 2,000 calorie storage of carbohydrate fuel, would you do it?
LeBron James did it by switching to a ketogenic diet.
But for those of us who aren’t athletes, can the ketogenic diet positively impact our health?
The controversial ketogenic diet
A ketogenic diet is a diet high in fats and very low in carbohydrates (less than 50 grams of carbs per day) and causes the body to start burning fat instead of carbohydrates by breaking down fat into molecules called ketones. As we saw in last month’s article, “The Basics of the Ketogenic Diet,” the diet was developed to help treat seizures in children who suffered from epilepsy.
Believe it or not, the brain, usually dependent on glucose from food, can also run using ketones. When you transition to a ketogenic diet, there is a period of time in which your body adapts to the change. Under normal circumstances, skeletal muscle will burn ketones for energy, but as “keto-adaptation” occurs, the muscles switch to burning fatty acids instead. This increases blood ketone levels and allows more ketones to supply energy to the brain. The change in energy sources makes keto-adaptation a gradual process taking at two weeks instead of a few days.
Today some nutritionists believe the ketogenic diet can be a valuable method for improving some health “biomarkers,” or signs of health your body creates. By examining these biomarkers, effects of the ketogenic diet can be measured.
In this part one of the three-part series on “How Does a Ketogenic Diet Affect YOU” we will look at what ketosis does for fasting glucose and insulin.
The ketogenic diet does what to my fasting glucose and insulin?
When we eat food, the carbohydrates we eat are converted to glucose and transported throughout the body to give us energy. Fasting blood glucose (sugar) measures the amount of glucose one has in his blood after fasting for at least eight hours.
Normally after we eat, our blood glucose increases as carbohydrates are digested. Then, sensing glucose in the blood, the hormone insulin is released which allows glucose in blood to enter cells and be used as energy.
However, on a ketogenic diet, there is very little carbohydrate. In this case, what happens to fasting glucose and insulin?
One study, published in the journal Nutrition and Metabolism, reported that people on a very low-carbohydrate, high-fat, low-calorie diet experienced decreased insulin levels. This was significant, because another group, also eating low calorie, but consuming a high-carbohydrate, low-fat diet did not experience the same level of change. There was a third group of men who ate a low calorie diet that was high in carbohydrate and high in unsaturated fats. All three groups ate low-calorie diets for eight weeks, then increased their calories to maintain their weight for another four weeks.
All groups experienced a decrease of 2% in fasting glucose with weight loss, independent of diet. Yet, those eating the very low-carb diet experienced a 33% decrease in fasting insulin concentration. This high-unsaturated fat diet had a decrease of only of 19% and the very low-fat diet experienced a 15% increase.
Post-meal insulin (as opposed to “fasted” insulin) was also lower in the low-carbohydrate diet group than in the other two groups. Researchers suggested that the high amount of fat may have delayed gastric emptying (when food leaves the stomach and enters the small intestine) of protein and weakened the release of insulin.
The study concluded that as long as there is weight loss, carbohydrate-restricted diets might be more effective than traditional weight loss diets in improving fasting and post-meal glucose concentrations and improving insulin sensitivity (which means how well body tissues “listen” to insulin and take in glucose from the blood).
Another study, published in the journal Experimental & Clinical Cardiology, examined the long-term effects of the ketogenic diet on weight loss and fasting blood glucose, as well as other various biomarkers, in 83 obese individuals. The ketogenic diet consisted of 20 – 30 g of carbohydrate (green vegetables and salad) and 80 – 100 g of protein (meat, fish, eggs, cheese, fowl and shellfish). Polyunsaturated and monounsaturated fats were also included. After 12 weeks, 20 g of carbohydrate were added for a total of 40 – 50 g of carbohydrate.
The subjects underwent fasting blood tests following eight, 16 and 24 weeks of treatment. Among other biomarkers looked at, the study found a significant decrease in the level of blood glucose, especially at week 24. The researchers concluded that using the ketogenic diet for a relatively long (24 weeks) period of time is safe. Yet, further studies need to examine the molecular basis of nutritional ketosis as this will help determine the potential therapeutic benefits from a ketogenic diet.
As we see, a ketogenic diet may decrease both fasting glucose and insulin concentrations, with a potential increase in insulin sensitivity (how well our cells uptake glucose).
So why is this important to people? When carbohydrate consumption is restricted below a threshold in which it is not converted to fat, insulin sensitivity can often improve because less glucose is coming in. This is especially important for diabetic individuals because insulin resistance (the inability of muscle cells to take in glucose) is the main feature of type 2 diabetes.
Yet, diabetics are not the only ones who should monitor their fasting glucose and insulin. It’s important to control our blood sugars because type 2 diabetes develops over time when our body either doesn’t produce enough insulin or our body can’t use it properly. And if our body cannot use insulin, glucose remains in our blood at higher levels than normal, and this can cause many health complications.
How do you know what is a normal level? A normal level in fasting (of at least 12 hours) blood glucose test should be between 70 and 100 mg/dL. A level between 100 and 125 mg/dL is considered prediabetic and a level higher than 126 mg/dL signifies diabetes.
It’s important to keep in mind that every individual is different and may respond differently to the effects of this diet. Restricting carbohydrates can be very difficult. Therefore, focusing more on “good” carbohydrates, such as those with high fiber, may be a good option if you’re wondering what to do with this information, especially if you do not want to restrict carbohydrates. In the next part of this series, we’ll look at cortisol (the “stress hormone”) to see whether it goes up or down when the body adapts to nutritional ketosis.
Katie Mark is a first year Nutrition Communication student from Miami, Florida. She is a Cuban coffee connoisseur and has traveled to Cuba, where she hopes to live one day.