Intermittent fasting has been one of the most popular health trends of the past decade. Some people swear by the eating pattern, finding that it helps manage their appetite, weight and to support optimal health.
Intermittent fasting is generally considered safe. However, it is best to use caution when beginning or following the eating routine.
Restricting your calorie intake for an extended period of time could be dangerous for:
- children and adolescents
- people who are pregnant or breastfeeding
- people who have diabetes
- people taking certain medications
- people with a history of eating disorders
Before embarking on intermittent fasting or making any other drastic changes to your diet, consult a trusted healthcare professional to help you get started safely.
What is intermittent fasting?
Intermittent fasting is an eating pattern during which you refrain from consuming any calories for an extended period of time. Usually, this period lasts between 12 and 40 hours.
Water, coffee, and other calorie-free beverages are allowed during the fast, but no solid foods or calorie-containing drinks are permitted.
Here are 5 of the most popular eating patterns for adding intermittent fasting to your diet:
- Time-restricted eating. Involves fasting every day for 12 hours or longer and eating in the remaining hours. A popular example is the 16/8 method. It features a daily 16-hour fast and an 8-hour eating window wherein you can fit in 2, 3, or more meals.
- The 5:2 diet. Involves eating as you normally do 5 days of the week and restricting your calorie intake to 500–600 on the remaining 2 days.
- Eat Stop Eat. Involves a 24-hour fast once or twice per week.
- Alternate-day fasting. The goal is to fast every other day.
- The Warrior Diet. This was among the first popular diets to include a form of intermittent fasting. It involves eating small amounts of raw fruits and vegetables during the day and eating one large meal at night.
Pros of Intermittent Fasting
Might support weight loss and improve metabolic health
Two main reasons why people try intermittent fasting are to manage their weight and metabolic health. Metabolic health is a marker of how well the body processes, or metabolizes, energy. It’s often measured by blood pressure, blood sugar, and blood fat levels.
Fasting or abstaining from food can create a calorie deficit, meaning that your body has fewer calories than it needs to maintain its current weight. That’s why diets that rely on calorie restriction, like fasting, are the hallmark of most weight loss diets.
Time-restricted eating routines similar to the 16/8 method are one type of intermittent fasting that has been linked directly with weight loss. Alternate-day fasting and the 5:2 diet may also be effective.
Besides naturally eliminating your calorie intake during the fasting period, intermittent fasting may support weight loss by regulating your appetite to increase feelings of fullness while suppressing feelings of hunger.
The eating pattern has also been linked with other improvements in health, such as: lowering blood pressure, improving blood sugar, repairing damaged cells and protecting brain health.
Can be a sustainable lifestyle change
Intermittent fasting doesn’t typically require calorie counting, eatingcertain foods that you might not be used to eating, or eliminating certain foods that you otherwise enjoy.
For example, having an early dinner followed by a late breakfast the next day is one way to fast intermittently. If you finish your last meal at 8 p.m. and don’t eat until noon the next day, you’ve technically fasted for 16 hours.
Works well with a nutritious, whole foods diet
Because intermittent fasting is focused more on when rather than what you eat, it’s generally easy to implement in conjunction with your current diet. You won’t necessarily need to buy any special foods or diverge much from what you typically eat.
If you’re already content with the state of your current diet but looking for other ways to continue boosting your overall health, fasting might be something you want to explore.
Cons of Intermittent Fasting
Here are a few downsides you could encounter when first trying intermittent fasting.
Might go against your intuition - intermittent fasting requires discipline, restraint, and planning ahead.
For some people, using those tactics to keep your calorie intake within a designated time frame is no problem, but for others, it might feel unnatural at first. This may be especially true if you’re used to relying on your intuition to decide when to eat.
What’s more, if your schedule tends to vary from day to day because of work, family, or other obligations, keeping your calorie intake to a designated time frame could be challenging.
You’ll likely feel hungry - even an 8- or 12-hour fast might feel like a long time when you’re not used to fasting.
You may go to bed hungry several times per week. That may naturally feel unpleasant and unsustainable in the long term. This doesn’t mean that fasting isn’t a schedule you can get used to.
Once you’ve adjusted to intermittent fasting, you might even find it makes you feel less hungry.
Many people adjust to the routine, and some even find they enjoy it after a few months. Yet, hunger and frustration are certainly something to expect and be aware of initially.
The side effects could affect your mood
When you first try intermittent fasting, one of the first things you may notice — aside from feeling more hungry — is ups and downs in your mood. This is understandable. Besides initially increasing hunger levels, fasting can have side effects, including headaches, constipation, fatigue, sleep disturbances, and more.
What’s more, irritability and anxiety are classic symptoms of low blood sugar levels. This is a common bodily response to fasting or restricting calories. Still, like hunger, your emotional well-being may be another side effect of intermittent fasting that will improve with time and practice. Once you’ve had time to adjust, intermittent fasting may even bring you a sense of achievement or pride.
Intermittent fasting is a weight loss tool that works for some people, but not everyone.
It’s not recommended for individuals who once had or currently have an eating disorder. It may also be unsuitable for children, people with underlying health conditions, and people who are pregnant or breastfeeding.
If you decide to try intermittent fasting, remember that just like with any eating pattern, diet quality is key.
To gain the most from intermittent fasting, be sure to eat a variety of nutrient-dense whole foods during your eating window and limit ultra-processed foods.
Furthermore, before embarking on an intermittent fast, be sure to consult a trained healthcare professional to ensure that it’s safe for you to do so.