Keto and intermittent fasting (IF) have taken fitness, nutrition, and weight loss communities by storm. Avid followers of these diets all claim miraculous results, like rapid weight loss, improved cognitive function, and a healthier cardiovascular system.
However, with research finding that restrictive eating practices can make an individual more susceptible to weight gain, the question remains: Are keto and intermittent fasting diets good for weight loss?1
An Overview of the Keto Diet
The keto diet was initially developed as part of a treatment plan for children with epilepsy, but its purported benefits have since expanded to include weight loss support.11 As a high-fat, very low-carb eating pattern, the keto diet aims to help your body reach a metabolic state of ketosis in which your body turns to ketones for a fuel source.
As your body breaks down the fat from your food sources or the fat stored in your body, ketones form. Popular keto resources suggest limiting your carb intake to 5 to 10% of your total daily calories. For a 2,000-calorie diet, this translates to 50 grams of carbohydrate max.
Some of the health benefits of keto include:
- Improved muscle health
- Enhanced glucose levels balance
- Better brain health
- Protection from brain-related diseases
Does Keto Work for Weight Loss?
One particularly interesting study found that participants on a keto diet lost more fat around their midsections than a control group on a different nutritional plan.2 A large amount of visceral belly fat has been linked with inflammation, so losing fat in this area can have other benefits to your health outside of weight loss.
In addition, other studies have found that, while in ketosis, insulin levels are minimalized, helping to improve insulin sensitivity.3 Not only does this promote fat-burning activities within the body, but it also can reduce the risk of developing diabetes and improve your fasting glucose levels.
While keto and weight loss seem to go hand in hand, research also shows that restricting food types often causes people to feel out of control when they are “allowed” those foods again.4 This can lead to greater weight gain when people stop following the keto diet or reduce the benefits of the diet if they like to use “cheat days” to stay on track.
Changing the primary source of energy from carbohydrates to fat can help you control your blood sugar levels. However, the keto diet could be potentially dangerous if you have type 1 diabetes and allow your ketone levels to rise above normal.5
A research review on the effects of ketosis on type 1 diabetics notes that elevated ketones parallel the impact of high glucose levels in diabetics, who have increased ketone production and decreased ketone clearance. This can be attributed to inherently low insulin levels (insulin is required for ketone clearance), the review says. The side effects of this can include oxidative stress and damage, effects on insulin secretion and resistance, inflammation, and liver dysfunction.
This is rare with type 2 diabetes; however, it can still occur.6
With that in mind, if you’re living with diabetes and considering the keto diet, you need to take extra care in monitoring your blood sugar levels and, ideally, testing your ketone levels, too.
An Overview of Intermittent Fasting
Intermittent fasting is a dietary pattern designed to incorporate brief periods of fasting into your routine. Unlike traditional fasting (often practiced for cultural or religious reasons), which can last days or weeks, intermittent fasting focuses on short-term fasts and offers more flexibility.
With IF, you’re focused on when you eat instead of what you eat. Many people prefer this type of plan because it allows them to reap the benefits without restricting their favorite foods. With other diets, such as the keto diet, people are constrained to a very small number of foods. This lack of variety can make long-term adherence to the diet difficult. If you enjoy a wide variety of foods and don’t mind limiting when you eat, IF may be a good option for you.
Some benefits of fasting include:
- Reduced calorie intake
- Improved metabolic health
- Better blood sugar level control
- Autophagy and cellular cleansing
Does Intermittent Fasting Work for Weight Loss?
Intermittent fasting and weight loss aren’t a clear-cut relationship. While you can lose weight following an IF regimen, there are no significant differences between IF and other diets in terms of weight or body fat loss.8
As we mentioned earlier, intermittent fasting works by restricting when you can eat, so naturally, you will eat less during the day.
However, given that you have no restrictions on what you can eat, this diet doesn’t help you to eat healthier foods or improve your diet. It’s entirely possible that you can follow IF and maintain or even gain weight. Again, as one previously mentioned study showed, a psychological restriction can increase the amount of food you’re driven to eat.
As with keto, IF hasn’t been around for long enough for there to be any meaningful study of its long-term effects on weight loss.
It’s also important to note that while intermittent fasting has been shown to improve insulin resistance, this diet can make managing your blood sugar particularly difficult. In particular, long periods without food can cause your blood sugar levels to drop too low. When this happens, the liver aims to release a surge of stored glucose.
While this study suggests that intermittent fasting is safe for people with diet-controlled diabetes, it concludes that people who take insulin or other medications should consult a doctor before starting an IF diet and should carefully monitor their blood glucose and ketones.9
Can You Do Keto and Intermittent Fasting Together?
One of the biggest criticisms of IF is that it doesn’t restrict what you eat, which is why many people pursuing weight loss combine IF with another diet. Keto is a particularly popular choice.
Make no mistake—combining these two diets will work on the simple premise that you’re consuming fewer calories than you’re used to eating.
One study even found that a combined approach of keto and IF helped one woman with type 2 diabetes to control her blood sugars without medication after 14 months.10 The study found a combined approach helped to reduce her blood glucose levels and lose a small degree of weight.
However, this study only covered one individual. It’s also worth noting that this individual received full medical support alongside her keto and IF diet, so these same results may not be applicable outside of this case study.
Because both diets are particularly restrictive, you might also find it overwhelming to stick to them in combination. You might also find that this high degree of restriction doesn’t help you to learn healthier habits.
Potential Benefits and Challenges of Combining Keto and Intermittent Fasting
There are some potential benefits of combining keto with intermittent fasting, including:
Keto can make the transition to IF easier
If you are going to pair IF with another eating style, keto is the ideal choice, as the fullness you may experience after eating high-fat foods could keep your body satiated for the fasting window. Starting keto first and then adding IF to the mix is the easiest route. Your body will experience less of a shock when adding in IF since your metabolism has adapted to utilizing fat and ketones for energy.
IF can aid ketosis
Fasting is a great tool to support the keto diet as it can kickstart ketosis and help your body stay in ketosis for longer. This is because fasting stimulates the body’s ketone production by utilizing your glucose stores.
However, there could be some challenges with incorporating the two eating styles. For one, it is a big shift from “normalized” eating. You may find it easier to start with one eating style and then gradually adopt the second one.
Do Keto and Intermittent Fasting Work for Weight Loss?
Keto and intermittent fasting do work for weight loss, but it’s important to understand the risks of following these highly restrictive diets, particularly if you need to monitor your glucose levels to help you manage diabetes.
The key to long-term weight loss isn’t just finding a diet that helps you lose weight but one that teaches you healthy habits to help you keep the weight off. Many diets only focus on helping you achieve short-term results, and many diets aren’t sustainable.
While some people find an IF, keto, or combination diet that works for them, everyone has different nutritional needs. You might find that keto and IF don’t work for you, and that’s perfectly normal. Not everyone can sustain a restrictive diet, and it’s important to find a nutritional plan that works for you and your goals.
As always, if you’re considering starting a new diet for weight loss, consult a healthcare professional first, particularly if you need to monitor your glucose levels for medical reasons or have specific medical conditions that need to be taken into consideration.
Who Shouldn’t Do Keto or Intermittent Fasting?
Keto and IF can potentially be hazardous if you have certain health conditions, such as diabetes, because of how they affect your blood sugar levels. You’re particularly at risk of conditions like DKA or hyperglycemia if you use medication to control your blood sugar levels. So, if you have diabetes and you’re considering keto, IF, or both, speak to your doctor.
If you’re pregnant or breastfeeding, we also don’t recommend that you attempt a keto or IF diet without consulting your doctor. Pregnancy and nursing require a higher caloric intake to sustain yourself and your child, so attempting to undergo a calorie restriction can be hazardous for you and your baby.
Similarly, anyone under 18 shouldn’t attempt intermittent fasting or keto, as they have a higher calorie requirement.
Finally, if you’ve got a history of eating disorders or disordered eating in any capacity, we don’t recommend following intermittent fasting or keto. Intermittent fasting, in particular, can trigger overeating and binge eating. Deregulating your appetite by attempting these diets can also trigger a resurgence of previous disordered eating behaviors.
How to Combine Keto and Intermittent Fasting Safely
You may be wondering how to combine intermittent fasting with the keto diet. Below are some tips to get you started.
Pair adequate protein intake with strength training
Research has shown that time-restricted eating (TRE) could lead to loss of muscle mass when exercise is not involved in the equation.12 However, adding in strength training and eating protein can mitigate this muscle loss. It is recommended to aim for 1.2 to 1.6 grams of protein per kg of body weight. Protein will also help with appetite management and allow you to feel more sated during your fasting windows. Aim for whole food sources like eggs, meats, and seafood, or high-quality plant protein options if you are vegan or vegetarian.
Choose a whole-food keto diet
Cutting back on processed foods will help you decrease the chances of overeating. Many “keto approved” snacks are high in processed ingredients, so be sure to check the nutrition labels of any products before purchasing. Opting for whole foods will nourish your entire body and allow you to ensure adequate intake of essential vitamins and minerals.
Make sure you keep hydration levels high
Both IF and the keto diet can lead to electrolyte imbalances by suppressing insulin.13 Insulin helps with sodium reabsorption, so if it is suppressed, you will be sweating out sodium and potassium without replenishing these stores. Drinking water will help correct these possible imbalances and prevent dehydration.
Set an eating window
One of the most classic time windows for IF is to eat when the sun is out and avoid eating two to three hours before bedtime. Based on your schedule, lifestyle, and preferences, this may not work for you. Research shows that if you are trying to optimize your metabolic health and glycemic control, eating earlier in the day is best.14 However, it is more important to pick an eating window that you can commit to consistently.
Keto and Intermittent Fasting Sample Meal Plan
If you are interested in trying both keto and IF, below is a sample diet plan that focuses on combining keto with 16:8, the most beginner-friendly form of fasting. More ideas can also be found in this IF meal plan blog article.
9:00 am- Omelet with cheddar cheese and mushrooms, black coffee
1:00 pm- Avocado salad with a keto protein shake
5:00 pm- Air fryer chicken wings with broccoli and cheese
9:00 am- Coconut and almond flour pancakes, black coffee
1:00 pm- Ground beef and cabbage, sugar-free lemonade
5:00 pom- Tuna patties, avocado slices, cauliflower florets
9:00 am- Breakfast casserole (sausage, cheese, broccoli, heavy cream, spices), black coffee
1:00 pm- Pork tenderloin wrapped in bacon, keto smoothie
5:00 pm- Salmon with garlic and butter sauce
We recommend working with a registered dietitian to determine specific macros and meal ideas to meet your goals.
FAQs Around Keto and IF
Can I do intermittent fasting if I have diabetes?
In individuals living with type 2 diabetes, intermittent fasting has been proven to lower fasting glucose levels by 5.6%.15 Also, it has been found that fasting increases insulin sensitivity.15 However, you should always consult your healthcare provider before starting a fasting eating plan, especially if you are living with diabetes.
How many hours should you intermittent fast on keto?
The most popular fasting time is the 16/8 method, where you have a 16-hour fast window, and eat during the 8 hour window. Many people eat two to four times during this window.
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Topics discussed in this article:
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