What is Intermittent Fasting?
Intermittent fasting (IF) is an eating pattern that involves cycling between periods of fasting and eating. It has become an incredibly popular way to lose weight, improve health, and simplify eating habits. The most common methods involve fasting for 14-18 hours per day, restricting eating to certain hours, or fasting for 24 hours 1-2 times per week.
Popular Intermittent Fasting Schedules
Here are some of the most popular IF schedules that people follow to lose weight:
- 16/8 method: Fast for 16 hours per day, eat all food within an 8 hour period.
- Eat-Stop-Eat: Fast for 24 hours once or twice per week, eating normally on the other days.
- 5:2 diet: Eat normally 5 days per week, restrict calories to 500-600 on 2 days.
What is the Ketogenic Diet?
The ketogenic or "keto" diet is a very low carb, high fat diet that shares similarities with low carb diets like the Atkins diet. The goal is to get your body into a metabolic state known as ketosis, where your body starts burning fat for fuel instead of carbs.
On keto, you restrict your net carb intake to under 50 grams per day. Net carbs are total carbs minus fiber. On such a low carb intake, your body eventually runs out of carbs for energy and begins breaking down stored body fat into molecules called ketones.
Ketosis for Weight Loss
The state of ketosis allows your body to become incredibly efficient at burning fat stores for energy. In ketosis, your body essentially turns into a fat burning machine, helping you lose excess weight. Ketosis combined with calorie restriction has been shown in studies to result in rapid, sustainable weight loss.
Why Combine Intermittent Fasting and Keto?
Intermittent fasting and the ketogenic diet lead to similar metabolic changes and health benefits, so combining them may have a synergistic effect.
Here are a few of the ways these two strategies complement each other for weight loss:
Better Appetite Control
Both IF and keto naturally suppress hunger and lead to reduced appetite. Combining fasting with ketosis may allow you to go longer periods without feeling hungry or needing to eat.
Increased Fat Burning
Fasting and keto both cause your metabolism to start preferentially using fat for energy. Combining the two may help boost fat burning and make it easier to maintain ketosis.
Less Muscle Loss
Keto diets lead to a natural reduction in appetite. You may need to force yourself to eat enough calories and protein to prevent excessive muscle loss. Adding IF prevents long periods without nutrients to help preserve muscle.
Is Fasting Safe on Keto?
Yes, intermittent fasting is considered safe for most people on the ketogenic diet. However, you may need to take some extra precautions to make sure fasting fits your needs.
Watch Your Calories
Make sure you eat enough calories to fuel your day and prevent excessive hunger leading to bingeing later.
Stay Hydrated
Drink extra water, broth, electrolytes and caffeine-free teas while fasting to prevent dehydration.
Listen to Your Body
Pay attention to signs of low blood sugar like dizziness, nausea, shakiness. Break your fast if you feel unwell.
Supplement If Needed
Take electrolytes, protein powder or BCAAs during fasts if you feel fatigued or are working out.
following an 18 Hour Fast on Keto
Following an 18 hour fast while on the keto diet is safe for most people and may amplify the weight loss effects.
Sample Schedule
6pm - Finish eating last meal of the day
8am (18 hrs later) - Break fast with bulletproof coffee or keto breakfast
6pm (12 eating window) - Finish dinner and begin 18 hour fast again
Tips to Follow an 18 Hour Fast on Keto
- Stay busy and distracted from food cravings by working, exercising, socializing.
- Supplement with electrolytes if you feel depleted while fasting.
- Drink plain or sparkling water, unsweetened tea, black coffee.
- Go to bed early so you sleep through much of the fast.
- Break your fast slowly with fat and protein to stay satisfied.
Potential Side Effects To Be Aware Of
When combining intensive fasting with very low carb intake, there are some temporary side effects some people report initially.
Here are some of the possible issues that may arise when fasting and doing keto:
Keto Flu Symptoms
As your body adapts to ketosis, you may experience things like moodiness, headache, fatigue, muscle cramps. Hydrating and supplementing with electrolytes can offset these.
Heart Palpitations
Some people notice harmless extra heart beats or palpitations while transitioning into ketosis. Staying hydrated helps, but check with your doctor if it persists.
Constipation
To avoid constipation from dehydration or very low carb intake, make sure to drink plenty of fluids, opt for low carb vegetables like greens and supplement with magnesium.
Who Should Be Cautious When Combining Fasting & Keto?
Intermittent fasting and ketogenic diets are very safe for most healthy adults. However, some groups should take extra precautions or avoid either strategy.
People Who Should Be Cautious:
- Those with a history of disordered eating.
- Anyone with Type 1 Diabetes.
- Women who are pregnant or breastfeeding.
- Those taking prescription medications.
- People with low blood pressure.
- Anyone underweight or malnourished.
If you have any medical conditions or take medications, check with your healthcare provider before starting intermittent fasting or a ketogenic diet.
Sustainable Lifestyle Change
Rather than a short term diet, many people find success by sticking to intermittent fasting and keto for weight maintenance long term. Making this an easy routine can prevent weight regain.
Tips for Sticking to Intermittent Fasting & Keto Long Term:
- Find a fasting and eating schedule that fits your lifestyle.
- Make sure you get enough calories and nutrients on eating days.
- Stay hydrated and balance electrolytes while fasting.
- Plan keto-friendly snacks or small meals if needed.
- Allow yourself a break from strict keto or fasting if you feel burnt out.
The long term combination of intermittent fasting, whether 18 hours or another schedule, along with keto may help manage weight, prevent chronic disease, and support overall health.
FAQs
What is the best intermittent fasting schedule to follow with keto?
The 16/8 fasting schedule where you fast for 16 hours and eat within an 8 hour window is a popular option to pair with keto. An 18 hour fast followed by a 6 hour eating window is also commonly followed by people combining fasting and the ketogenic diet.
Will fasting cause muscle loss while on keto?
You may lose some muscle if following fasting and keto long-term without enough protein intake. Make sure to eat sufficient protein and calories during eating windows to help preserve muscle mass while fasting on keto.
Can I exercise while fasting on the keto diet?
You can exercise during fasting periods on keto but you may need to shorten your fasting times on workout days to avoid severe fatigue. Make sure you supplement with electrolytes and eat enough calories when you do eat while training fasted on keto.
Is intermittent fasting necessary for ketosis?
You do not need to fast to reach or stay in ketosis. However, fasting may help some people boost ketone levels, control appetite for ketogenic diets, and accelerate weight loss results while on the keto diet.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.
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