Keto Versus Intermittent Fasting: Which is Best?

When it comes to weight-loss diets, both the keto plan and an overnight intermittent fasting plan are effective weight-loss strategies — for the short term, anyway. People swear by one or the other, but as a wellness dietitian, I want to point out a few of the hidden costs of the ketogenic diet in contrast to some of the benefits of an overnight intermittent fasting regime. Just hear me out on this one!


Keto Diet Overview: Low Carb, High Fat


The ketogenic diet, also called a ketosis diet or keto for short, is a way of eating that mimics the effects of fasting. During fasting, body fat is metabolized, which makes ketones that the body uses for fuel rather than glucose from food.

In an attempt to force the body to use ketones for energy on a ketosis eating plan without fasting, dietary fat replaces carbs in the diet. Thus, the keto diet is very high in dietary fat (typically 70 to 80 percent of your total calories), while very low in carbs (less than 5 percent). This low carb intake eliminates refined grains and sweets from the diet, along with many vegetables, fruits, beans, lentils, and whole grains.


Without carbohydrates to use for energy, your body is forced to use fat to produce ketones as the primary energy source. On a ketosis diet, the primary source of fat used to produce ketones is from the fat you eat, not body fat as occurs in fasting. *


Many assume that protein consumption is unlimited when following a ketogenic diet. But since the body converts extra protein to glucose to use for energy, only moderate amounts of protein (about 15 to 20 percent of total calories) can be eaten to keep your body burning ketones for energy.

Valuable Nutrients Lacking in a Keto Diet

Eliminating whole food groups from your diet is a dietitian’s nightmare! Why? Because the body needs these critical nutrients to function properly. Avoiding a variety of fruits, vegetables, beans, lentils, whole grains, and specific dairy products (like yogurt without added sugar) that contain “good carbs” has significant health impacts over the long term such as suppressed immunity, poor gut and bone health, risk of dehydration and many more.


The scientific research is full of studies pointing to the importance of eating half of your food in fruits and vegetables to decrease the risk of disease, boost your immune system, and even help preserve your thinking and memory skills. Yes, that’s right; 50 percent of the food you eat should be a variety of produce. Fruits and vegetables are full of not only vitamins and minerals but also fiber and thousands of phytochemicals that work together synergistically — in ways we don’t yet understand — to improve your health and weight.


With limited fruit and vegetables, whole grains, and legumes, people miss out on fiber, specific vitamins, minerals, and phytochemicals that only come in these foods and that are essential for gut health. Not only do these foods feed the good bacteria in your gut to improve your microbiome, but constipation commonly results without these valuable carbohydrate foods in your diet.


Important electrolytes, such as sodium, magnesium, and potassium, are found in fruits, beans, starchy vegetables, and yogurt, which are restricted on a ketosis eating plan. In addition, ketosis causes you to urinate more and lose valuable electrolytes. It’s no wonder the body is oftentimes low in electrolytes and subject to dehydration when following a ketogenic diet. Besides dehydration and lightheadedness, keto dieters are prone to kidney injury and kidney stones. Electrolytes are critical for the heart to beat correctly, so ketosis dieters may be at risk for cardiac arrhythmia, too.

Since ketones produced during the breakdown of fat are acidic, the blood becomes acidic, and the body compensates by pulling minerals from bones. Over time, calcium loss can lead to increased fractures, low bone density, and osteoporosis.


Keto Diet and Food Shaming


While following a ketogenic eating pattern and avoiding so many health-promoting foods, it’s easy to begin to think of eliminated foods as “fattening” and “bad” for you. Feeling guilty about eating a highly-nutritious apple or a sweet potato is problematic for your health. Your body needs those health-promoting foods to help you think and function. But even when people have stopped following the diet, there is often a continued sense of shame when eating nutritious carbohydrate-containing foods such as fruit, many vegetables, whole grains, and yogurt. At the very least, there is a lingering mindset that these highly nutritious foods are to be avoided.


The keto plan focuses on how much and what can be eaten, rather than eating to satisfy hunger cues and eating quality foods in their whole food form. There is plenty of research that indicates that the key to successful and sustained weight loss is more about eating whole foods instead of processed, refined foods. Yet, one of the main problems of following a very low-carb diet is that people tend to eat a lot of processed protein and poor-quality fats, with very few fruits and vegetables and whole grains. Just as healthy carbohydrate food may be viewed by a ketosis dieter as off-limits and “bad,” these less healthy processed foods may potentially be seen as health-promoting and “good” for weight loss.


Keto Diet Obstacles


While your body adjusts to burning fat rather than carbs, the transition is often uncomfortable. Referred to as a “keto flu,” many people experience symptoms such as headaches, fatigue, nausea, irritability, hunger and brain “fog” lasting about a week. These unpleasant conditions do gradually decrease as your body gets used to converting ketones into energy, but during that time, it’s harder to be productive, function at work, and to exercise.


Ketosis Adherence and Sustainability


The rules on the ketosis plan are so rigid (for your body to be able to convert to burning ketones for energy) that it’s easy to throw in the towel with one slip up. It takes a few days for your body to achieve ketosis. But if you “cheat,” then your body is no longer in ketosis, and it takes another few days for your body to reestablish ketosis. This diet is difficult to adhere to, so it’s not surprising that the US News & World Report’s review of 2018 diets rated the ketogenic diet in the last place as a sustainable means to weight loss.


Because of the keto diet’s challenging nature, low adherence rates result. Quitting the diet can lead to binge eating to satisfy food deprivation, which can result in weight gain. An all-or-nothing dieting mentality often develops when dieters find themselves unable to adhere to a diet. When it comes to sustainability, the keto plan is a lose-lose!


A Preferred Alternative Diet: Intermittent Fasting


Intermittent fasting (IF) is a popular weight-loss method where no food or caloric drink is ingested for an extended window of time. Various IF approaches exist, but more human studies have helped researchers hone in on the more effective and sustainable way to undertake this type of weight-loss plan. Overnight fasting, in sync with your internal clock and light and dark cycles, is called early time-restricted feeding (eTRF) or prolonged nightly fasting. This time-restricted feeding method of IF begins early in the evening when your nighttime hormones kick into gear to help you sleep. Fasting ends in the morning when you eat breakfast, and when your body is naturally better at metabolizing your food.


Intermittent fasting starting early in the evening rather than later in the morning may reduce daily hunger cravings and burn more fat during the night. Fasting triggers the body to burn its stored fat, which produces ketones for energy and results in weight loss. Your body can make this switch from using glucose for energy to burning body fat stores to produce ketones after just 8 – 12 hours of fasting.


Depending on your schedule, going without food or drink (except water) for between 12 to 16 hours starting early in the evening on a fairly consistent basis as it fits your schedule can be a significant boost to your weight and health. For more specifics, read my article on intermittent fasting, entitled, “Best and Worst Time to Eat for Lasting Weight Loss.

Consuming Valuable Nutrients on an Intermittent Fasting Plan


When following an intermittent fasting plan, you have the opportunity to eat foods packed with nutrients, including a variety of fruits, vegetables, whole grains, and low-sugar yogurt that can improve your health. In fact, replacing processed foods with whole foods like fruits, vegetables, legumes, whole grains and water on an overnight intermittent fasting plan will help you lose even more weight and feel more satisfied than IF alone. You are not restricting any of these foods as you would be when following the ketosis plan.


Food Shaming: a Non-Issue on the Intermittent Fasting Plan


The emphasis in IF is centered on when you eat rather than what you eat, so food shaming isn’t an issue with this eating pattern as it is when following a ketosis diet. Healthy food habits can be adopted on the IF plan, but you also can choose to have a treat to minimize feelings of food deprivation.

High fat, high protein processed foods are not given a confusing health halo when following an IF plan, which often happens on a ketosis diet plan. An IF plan doesn’t oppose the established research in regard to the harmful effect of processed foods or benefits of nutrient-dense foods on your weight and health.


Intermittent Fasting Obstacles


While following an overnight IF plan, your body naturally shifts to burning fat during the night, especially if food hasn’t been consumed in the evening. Your body doesn’t need to adjust to using an alternative fuel source to function during the day, as it does during ketosis. Therefore, you don’t experience the uncomfortable symptoms your body experiences on a ketogenic plan. In fact, eating more produce and healthy whole grains gives you more energy to exercise and feel great instead of eating a higher fat, processed food that can make you feel lethargic!


The shift to eating more in the morning on the IF plan instead of the evening may be a challenge for some. Many traditional non-breakfast eaters tend to eat in the evening, but find they become hungrier in the morning when they are not eating in the evening.


There is some leeway on fasting times to help with the adjustment of eating more in the morning and ending intake earlier in the evening. You don’t need to eat breakfast right after you wake up, for instance. Eating breakfast two to three hours after you wake up is a way to ease into this extended overnight fasting plan. The earlier you stop eating at night, the earlier you will want food in the morning. Your body will adjust, but it may take some time to become comfortable with these eating times.


Intermittent Fasting: Adherence and Sustainability


An overnight fasting plan is rather easy to stick to since people are sleeping the majority of the fast, and there is flexibility in when you stop and start your fast. Overnight fasting allows freedom to start fasting earlier in the evening on more convenient days. Fasts beginning later in the evening a couple of times a week do not sabotage the earlier fasting start times during the week. You can fast for 12 hours overnight some nights and longer on evenings when more convenient. The all-or-nothing mentality that coincides with a more restrictive diet plan, like the ketosis diet, is replaced with a more flexible, habit-forming approach that keeps extra weight off over time.


Overnight fasting allows you the freedom to eat how you choose. Without any off-limit foods, there is less chance of setting yourself up for failure or feeling deprived. According to scientific research, eating early in the day may help you alleviate hunger later in the day. Also, eating (not drinking) enough protein (somewhere between 30 – 40 grams) in the morning appears to help curb your cravings to eat less healthy food in the evening. You can make this overnight IF eating plan easier by selecting food and beverage choices that work with your body and your lifestyle. Less deprivation and better food choices make it easier to follow an overnight intermittent fasting regimen than a keto plan.


Fasting during the evening may also improve your sleep. Researchers found that people, especially women, who eat during the evening had lower quality sleep. Eating dietary fat in the evening (similar to a high-fat keto diet plan) disrupted sleep beyond merely eating food in the evening. Both men and women who consumed higher amounts of fat during the evening spent more time in bed without sleeping compared to those who ate lower-fat foods or had no food at all during the evening. Getting enough restful sleep can help you feel better the next day, encourage you to be more productive, and also help you lose weight more effectively.


The Winner, Please: Keto or Overnight Intermittent Fasting?


The ketosis diet and an overnight fasting plan (in sync with your circadian rhythms) are both effective weight loss methods. Which would you ultimately choose for lasting weight loss and better health?


An overnight version of the intermittent fasting plan beginning early in the evening and paired with breakfast encourages you to form positive eating habits without adopting misleading ideas about food. This type of overnight IF method is easy to stick to since you are sleeping much of the fast, and there is flexibility in the timing of your fasting regimen from day to day. In fact, avoiding food for 12 hours overnight most of the time throughout your life is doable and helpful for your future weight, sleep, and health.

Ketogenic diets, on the other hand, are short term at best and encourage an all-or-nothing dieting mentality that promotes up and down weight loss and possibly greater body fat stores in the long run.


Intermittent fasting offers an opportunity to eat a balanced, unprocessed diet, making overnight IF even easier to adhere to by allowing you to feel satisfied and avoid food cravings. This, along with all the other perks that go along with a healthier, whole food diet is a significant advantage. Yet sadly many of the healthier whole foods are limited or banned on a ketosis plan. 


Both plans can lead to weight loss, but overnight intermittent fasting (beginning early in the evening and ending with breakfast) is the winner for both continued weight maintenance and better long-term health!

*Steven Anton, PhD, FNCE Session, October 21, 2018, Chicago, Debate: Intermittent Fasting in Weight Management.

Judes Scharman Draughon, MS, RDN, LD is a corporate wellness dietitian nutritionist and author of Lean Body Smart Life: 12-Fix Plan to a Leaner, Healthier, Happier Life. She has narrowed down the scientific research to the 12 most significant “Fixes” you can do to make the biggest impact on your health, weight, and brain function. 

Judes inspires many with her high-energy nutrition presentations, workshops, and seminars. She resides in Durham, NC. If you are interested in having her speak with your organization or company, contact her at judes@foodswithjudes.com.