Luisa Torres, PhD
Luisa is a science communications manager at LifeOmic and neuroscientist and science writer covering topics related to aging, metabolism, and brain health.

Luisa Torres, PhD
Luisa is a science communications manager at LifeOmic and neuroscientist and science writer covering topics related to aging, metabolism, and brain health.


What is the keto diet | What is intermittent fastingCan you combine keto and intermittent fasting | Tips | What keto and fasting looks like 

What is the ketogenic diet?

The ketogenic diet consists in keeping carbohydrate intake very low. This means no sugar, no grains, and no refined carbs such as pasta and rice. On a keto diet you consume adequate protein, some fat, low-carb nuts and seeds, and non starchy vegetables and leafy greens.

For people wanting to lose weight and/or treat their type-2 diabetes, this diet is already a go-to. Limiting your carb intake forces your body to use fat for energy, which eventually normalizes blood sugar and increases sensitivity to insulin.

What is intermittent fasting?

Fasting is an ancient practice that involves avoiding calories for a period of time. It is a simple way to control your weight that doesn’t require you to eat specific food, count calories or measure food.

Similar to the ketogenic diet, intermittent fasting helps the body run out of sugar fuel until it has no other choice but to burn its fat stores.

Can you combine intermittent fasting and the keto diet?

Given the similarities between the ketogenic diet and intermittent fasting it’s worth asking: can you combine them? “I think they work phenomenally well together,” says LifeOmic’s Chief Medical Officer Dr. Shelagh Fraser. She is a practicing primary care physician in Indianapolis whose patients have seen great weight loss success with both interventions. She says the keto/fasting combination can be synergistic. Because you eliminate most carbohydrates with a ketogenic diet, you train your body to use fat for fuel, which makes it easier to tap into stored body fat when you’re not eating. Getting your body accustomed to burning fat is not only good for weight loss but it’s also great for your brain.  “A lot of people not only have plenty of energy, but they feel pretty intensely focused,” she says.

The combination may also work for those who are already healthy but want to eat better and possibly remain healthy longer. Minimizing blood glucose levels reduces the risk of cardiovascular disease and reduces the risk of mortality, explains Fraser. Less sugar also means lower insulin, which means less excess energy stored as fat. With these benefits, the second question worth asking is: how do you go about combining them?

We give you some tips below:

Tips for combining intermittent fasting and a keto diet

Do keto first, fasting second

The goal of the ketogenic diet is to lower carb intake to 20-50 grams per day, about a quarter of what the average American eats. Low carb intake helps the body make ketones, which diminish hunger. Fraser says it’s easier to get used to the ketogenic diet before adding on intermittent fasting. “If you do keto first, you avoid that sensation of hunger as you decrease your eating window.”

Young fit woman preparing a meal in the kitchen. She is slicing chicken while Zucchini slices are cooking in the stove. There are eggs, vegetables and a bottle of olive oil on the counter.
Getting used to a ketogenic diet first will help you avoid hunger during fasting.

Lisa Amorao, an open water swimmer and LIFE apps user who has been following a ketogenic diet since 2016, says the ketogenic diet helped her become aware of processed carbs. Once she eliminated them she stopped feeling hangry. “This meant that eating was no longer an emergency and I could take the time to shop and prepare food that I actually wanted to eat,” she says.

Due to ketones keeping you full longer, the ketogenic diet also makes longer fasts more doable.  LIFE apps user Elaine Pomerleau has been doing intermittent fasting together with a ketogenic diet for the past year, but she started following a ketogenic diet first. A few weeks later she added intermittent fasting, progressively increasing her fasting hours until she was able to do a 5-day fast. “I have lost 85 pounds, no more diabetes, no more fatty liver, and almost no polyarthritis,” she says.

Start slow

If you are new to the ketogenic diet, start by cutting out sodas and juices and eliminating candy bars. Next, avoid refined carbs such as rice, pasta, and bread until you’re eating 50 grams of carbs per day or less. Your carbs should come from complex sources, namely non-starchy vegetables such as leafy greens. “People always underestimate the amount of carbs they’re eating,” says Fraser. Keep track of your carb intake so you don’t go over the 50 gram limit.

Once you’re acclimated to the ketogenic diet, start with 14-16 hour overnight fasts, and gradually increase your hours if you’d like to fast longer. You can also start alternating between days in which you follow a ketogenic diet and days in which you add on intermittent fasting. “The more you can ease into it, the better,” says Fraser. Starting slow also applies if you are already doing intermittent fasting and want to start a ketogenic diet. Remove sugar and carbs slowly until you are eating no more than 50 grams of carbs per day.

Get adequate nutrition and learn about good fats and veggies 

A ketogenic diet can help you eat better, but this takes intention. “Many people think keto is a license to eat bacon and cheese all day,” says Fraser. “ You need to focus on also incorporating plants that are lower in carbs, such as nuts, seeds and leafy green vegetables.”

Take some time to learn about which foods are low-carb and which contain healthy fats. Good fats you can eat in a keto diet include:

  • fatty fish
  • whole eggs
  • full-fat greek yogurt
  • avocados
  • plant-oils (avocado, olive, coconut)
  • low-carb nuts and seeds such as flax and chia.

Some veggies have higher carb content than others. The best ones to eat in a ketogenic diet include:

  • broccoli
  • Brussels sprouts
  • cabbage
  • cucumbers
  • peppers
  • spinach.

You should also get adequate protein by eating meat and poultry (or tofu if you want to keep it plant-based).

High angle view of four different types of animal protein like a raw beef steak, a raw chicken breast, a raw salmon fillet and a raw pork steak on a stone tray surrounded by condiments, spices and vegetables. Low key DSLR photo taken with Canon EOS 6D Mark II and Canon EF 24-105 mm f/4L
Focus on incorporating good-quality proteins, low-carb vegetables, and healthy fats.

Pay attention to your body 

“It’s okay to experiment with whatever you’re doing and see what actually works best, because it is not exactly the same for everybody,” Fraser says. Pay attention and modify as needed. For example, you might measure how your blood sugar levels change in response to different foods using a continuous glucose monitor, or by measuring your blood or breath ketones. This can help you figure out what foods affect your blood sugar and ketone levels the most. For instance,  a serving of carrots might raise your blood sugar and reduce your ketones more than a serving of tomatoes.  “Unless you measure it, you will not know,” she says.

Fraser also recommends keeping track of how your sleep changes as you implement a ketogenic diet plus intermittent fasting.  Your sleep will be affected if you’re either feeling really hungry or really full at bedtime. This might mean, for example, that you need to eat earlier or later, depending on how your sleep is affected.

What keto and fasting looks like

We asked LIFE apps users to tell us how they combine intermittent fasting and a keto diet. Here’s what they told us:

Cherie Louise follows a 20:4 fasting schedule. Her typical meal is steak and eggs with a leafy greens, haloumi cheese, Greek yogurt, and some berries.

Cassandre Soriaux fasts for 16 hours a day. She usually eats meat or fish, veggies and some raw milk cheese.

Evangeline San Diego follows an 18:6 regimen. She loves cauliflower rice plus Salmon or Pork. She also loves strawberries and avocado.

Morgaine Swann fasts between 18 and 22 hours most days. Her meals are usually steak, chicken or ham, cheese, sour cream or cream cheese, and broccoli or brussels sprouts. She snacks on almond butter, pecans, hazelnuts, almonds or peanuts, and occasionally indulges in rebel ice cream.

Pam Brockus fasts for 16-20 hours a day and occasionally does a 60-hour fast. She eats lean meat, raw veggies and cheese for lunch, and meat and veggies for dinner.

Salad with grilled chicken breast, avocado, pomegranate seeds and tomato on white background. healthy diet food. Top view
A typical ketogenic meal for LIFE apps users consists of meat, veggies and avocado.

The above is not medical advice. Always consult with your doctor before trying a ketogenic diet, especially if you have type-1 or type-2 diabetes, or high blood pressure. A ketogenic diet with the intent of losing weight is not recommended for children. You shouldn’t practice intermittent fasting or follow a ketogenic diet if you are pregnant or breastfeeding. 

 


Luisa Torres, PhD

I'm a science communications manager at LifeOmic and the editor of this blog. I am a neuroscientist and science writer interested in covering topics related to aging, metabolism, and brain health. I have written for NPR's blogs 'Shots', 'Goats and Soda', and 'The Salt'.

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