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Keto diet

What is ketogenic fasting?

Nora Minno
"Eka is a qualified public health nutritionist with more than five years of experience in research. Aside from her researcher career, she is a freelance nutritionist and a copywriter, providing personalized nutrition advice and support to clients."

The keto diet is essentially a higher-fat, low-carb diet that forces the body to use fat as its primary source of energy, as opposed to glucose. On the keto diet, carbohydrate intake typically drops to about 5% of calories per day, or approximately 20-50 grams/day for most adults. Fat makes up the majority of calories consumed at about 70% and protein at about 25%[1].

Both dietary approaches have solid research behind them confirming various benefits such as weight loss, improved cognitive functions, and blood sugar control[2][3][4]. However, it’s important to note that there hasn’t been enough research yet to show that the synergy of the two leads to better results than cutting carbs or fasting alone.

Keto and intermittent fasting

To understand how ketogenic fasting might be helpful for your goals, be it weight loss or other health benefits, we should explore the logic behind keto and fasting as separate measures.

The keto diet: overview

The keto diet is essentially a higher-fat, low-carb diet that forces the body to use fat as its primary source of energy, as opposed to glucose.  On the keto diet, carbohydrate intake typically drops to about 5% of calories per day, or approximately 20-50 grams/day for most adults. Fat makes up the majority of calories consumed at about 70% and protein at about 25%[1].

Typically, your body uses carbohydrates as its primary source of energy. When your body is deprived of carbohydrates, as with the intake of less than 50 grams a day, it reduces insulin secretion and your body initiates certain metabolic processes. One of these processes is called ketogenesis. Genesis means “formation”, therefore ketogenesis means “formation of the ketone bodies.” Ketone bodies are produced by the liver from fatty acids and eventually replace glucose as the primary source of energy for the body including the heart the muscles, and the kidneys. 

As long as carbohydrate intake remains low (<50 grams/day), your body will remain in the metabolic state called “nutritional ketosis”. This state is generally considered safe as the concentration of ketone bodies is small and there are no changes in blood pH. The production of ketone bodies will depend on your BMI (body mass index), body fat percentage, and other factors, but generally ketosis allows your body to function effectively despite the carbohydrate deficit. 

There is a widespread belief that high-fat diets can cause weight gain and other ailments. However, studies have shown that those on low-carb diets typically lose more weight, most notably in the short term (<1 year) than those on low-fat diets[6]. Studies have also shown that low-carb diets are effective in getting rid of excess abdominal fat, which could, over time help reduce the risk for heart disease and type 2 diabetes.  As with any diet, it’s important to focus on the sources of your macronutrients. Foods like nuts, seeds, avocados, olive oil, and fish can be good sources of fat and part of a healthy diet.

However, the keto diet is not without risks and limitations. First, long-term benefits haven’t been established and the diet tends to lose its edge on other diets in areas like weight loss after the first year, Second, it involves risks of dehydration, electrolyte disturbances, nutritional deficiencies and hypoglycemia, and if followed, it should be done with caution.

Intermittent fasting: overview

The other player in the ketogenic fasting duo is intermittent fasting. Let’s explore the processes behind IF and its effect on weight loss, health, aging, and disease. You’ll quickly see that biological processes are very similar to the ones that happen while practicing a ketogenic diet.

Intermittent fasting is an eating practice that cycles between periods of eating, and periods of fasting or calorie restriction.

Typically after a meal, your body would convert carbohydrates, and other macronutrients,  into useable energy, and may store excess nutrients in different parts of the body like the liver, the muscles, and even in fat tissue.

When you reach a certain point in fasting, and your body isn’t getting any more glucose for energy, your body will break down stored fats to use for energy. The liver converts fatty acids into ketone bodies, and ketosis is achieved, which you should be familiar with by now. The production of ketone bodies in humans typically starts within 8 to 12 hours after the onset of fasting. 

There are three most common intermittent fasting regimes:

  1. Alternate-day fasting
  2. 5:2 intermittent fasting
  3. Daily time-restricted feeding

Refraining from eating according to the above schedules has been proven to be effective for weight loss. Other benefits, often noted with intermittent fasting are improvements in glucose regulation, blood pressure, and heart rate, as well as oxidative stress resistance. 

But the advantages of intermittent fasting ketosis don’t stop at that. There have been a number of different studies that explore the role of fasting in slowing down certain effects of aging and improvements in certain cognitive functions.

Finally, there are numerous clinical applications of intermittent fasting ketosis. It has been found to positively influence patients with obesity, diabetes, cardiovascular diseases, cancer, asthma, multiple sclerosis and arthritis.

What happens during ketogenic fasting?

Following a ketogenic fasting plan, would mean that one is following the traditional guidelines of a ketogenic diet (i.e. low carbohydrates, higher fat, moderate protein) and combining those principles with an intermittent fasting pattern over a period of time.

As mentioned before, there has been very little research on combining the two approaches, so anyone who tries ketogenic fasting should exercise additional caution.  

However, it’s hard to deny that combining keto and fasting makes sense. Both methods are underlined by the increased levels of ketones in the body. 

This means that for the followers of the keto fasting diet, the transition to the ketogenic state might happen faster when the methods are combined. For anyone that’s struggling to reach this metabolic state with the keto diet alone, adding intermittent fasting could do the trick.

Moving to ketogenic fasting from the keto diet might also be a natural solution for anyone who has reached the plateau in their weight and for those who feel satiated from eating all the fat the keto diet requires.

Ultimately, one could conclude that combining the ketogenic diet with intermittent fasting may lead to quicker and greater weight loss with all the subsequent health benefits.

Who should stay away from ketogenic fasting?

Ketogenic fasting is not just challenging, it involves risks and unknowns that are not yet studied. So for anyone who is seeking to try ketogenic fasting, it might be advisable to start with the keto diet alone for at least two weeks, then make a decision on how to progress.

It’s also advised to avoid this approach if you’re suffering from chronic kidney disease, have a history of eating disorders, are undergoing active cancer treatment, or are pregnant or breastfeeding. As with any major dietary change, it is recommended that you consult with a medical professional first.

[1] Low-carbohydrate diets: nutritional and physiological aspects

[2] Intermittent fasting could ameliorate cognitive function against distress by regulation of inflammatory response pathway

[3] Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males

[4] Effects of intermittent fasting on health markers in those with type 2 diabetes: A pilot study

[5] Effects of intermittent fasting on health markers in those with type 2 diabetes: A pilot study

[6] A Low-Carbohydrate as Compared with a Low-Fat Diet in Severe Obesity

[7] Effects of Intermittent Fasting on Health, Aging, and Disease

[8] Ketogenic Diet

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