For as long as she could remember, Suzy had been overweight. About a year ago, a friend introduced her to the keto diet, and for the first time ever, she experienced some weight loss success. When her weight loss plateaued after almost a year, Suzy started looking for a way to boost her metabolism. When she discovered intermittent fasting (IF), she lost another 10 pounds by combining intermittent fasting with keto. While both a ketogenic diet and intermittent fasting have become incredibly popular, many people still wonder whether they really work and, more importantly, whether it’s safe to combine them.
What is Intermittent Fasting?
Intermittent fasting is a type of diet approach that alternates between periods of consuming food and abstaining from food. The premise of intermittent fasting is that the human body taps into fat stores for energy when calories are restricted. Normally, the body relies on burning glucose from carbohydrates as its most direct fuel source. When glucose isn’t available, the body burns fat for energy. Since the body’s ability to store fat is unlimited, this happens even more with food deprivation.
None of the various ways to try IF are perfect. The type of fasting you try or the decision to fast at all should always be based on what works best for your body and lifestyle.
The Three Types of Intermittent Fasting Diets
While most diets focus on what to eat intermittent fasting is more focused on when you eat. During an intermittent fasting period, you only eat during a specific time of day. Whether you’re eating one meal two days a week or fasting for a certain number of hours each day IF can help your body burn fat. Read on to learn about the three most popular types of intermittent fasting.
5:2 Diet or Whole Day Fasting
The 5:2 diet, otherwise known as whole day fasting, is a type of intermittent fasting where you eat healthfully for five days of the week, and for two nonconsecutive days, you take in just 500 to 800 calories. Men typically aim for about 800 calories, while women aim for around 500.
IF on alternate days involves eating regularly one day, fasting (consuming less than 600 calories) the next, and repeating throughout the week. Water and broth are encouraged during fasting days to prevent dehydration.
Time-restricted fasting is a type of IF where you fast every day for 12 hours or longer. Time-restricted fasting follows a daily meal plan with a designated fasting time frame. For example, you consume food between 8 a.m. and 3 p.m., and you fast for the remainder of the day.
Is Intermittent Fasting Safe?
While many people use intermittent fasting for weight management, others use it to help relieve chronic health conditions like arthritis, high cholesterol, and irritable bowel syndrome. However, intermittent fasting isn’t for everyone.
If you’re thinking about starting any type of fasting, you should check with your primary health care provider, especially if you have a preexisting health condition. Certain people should never fast for prolonged periods of time, including:
- Children and teens under the age of 18
- Women who are pregnant or breastfeeding
- People with diabetes or blood sugar problems
- Those with a history of eating disorders
If you don’t fall into one of the categories above, it’s most likely safe for you to try intermittent fasting. You can continue IF indefinitely if you can fast safely.
The Benefits of Intermittent Fasting
Recent research has shown that intermittent fasting periods do more than just burn fat. One study published in the New England Journal of Medicine revealed a range of health benefits associated with IF. Below are some of the benefits highlighted in the research so far:
- Thinking and memory – Boosted verbal memory in humans and working memory in animals.
- Heart health – Improved resting heart rates, blood pressure, and other heart-related measurements.
- Physical performance – After 16 hours of fasting, young men were shown to achieve fat loss while maintaining muscle mass. Similarly, when mice were fed on alternate days, they showed better running endurance.
- Diabetes and obesity – In six brief human studies, obese humans lost weight through intermittent fasting alone. Similarly, animal studies showed that intermittent fasting prevented obesity.
- Tissue health – Animal studies concluded intermittent fasting reduced tissue damage and improved results in surgery.
How Does Intermittent Fasting Mix with the Keto Diet?
Intermittent Fasting Can Speed Up Ketosis
The keto diet is designed to kick-start ketosis by increasing your intake of fats and lowering carbs. Implementing intermittent fasting might mitigate some of the commonly occurring side effects of starting the keto diet, including the keto flu.
Who Can Safely Combine Intermittent Fasting with the Keto Diet – And Who Can’t?
Anyone who’s tried the keto diet for over two weeks with no adverse effects and wants to try combining intermittent fasting should be safe doing so.
However, it’s important to note that the keto diet has become popular among diabetics and prediabetics who shouldn’t fast for significant amounts of time because it can be dangerous for them. You should also steer clear of trying IF with ketosis if you have chronic kidney disease, if you’re a pregnant or breastfeeding woman, or if you’re undergoing active cancer treatment or have a history of eating disorders.
Whenever you’re considering trying a different dietary approach, such as IF with keto, it’s best to visit your healthcare provider first.
The Bottom Line
Although intermittent fasting may not be the right choice for everyone, it can be a safe and effective method for weight loss. Intermittent fasting has been shown to burn fat and boost metabolism while preserving lean body mass. When paired with diets like keto, IF might also accelerate ketosis while decreasing negative side effects.
Before you dive in, think about why you want to try intermittent fasting and your current eating habits and goals. What do you hope to achieve? For example, if you’re someone who snacks a lot at night, you could use intermittent fasting to set a cut-off time and help you eat less. Or, if you always eat your last meal of the day late in the evening, you could use intermittent fasting to eat earlier, allowing your body to start fasting then.
Above all else, it’s important to try diet methods that bring you happiness and don’t cause your body or mind any stress or harm.
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