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Intermittent Fasting: How it works

31 marzo, 2024

The world of diet and nutrition is full of trends, and one that has gained momentum is intermittent fasting. As intermittent fasting has gained popularity, more data is being rolled out that, in some cases, could support intermittent fasting as more than just a fad.

To better understand intermittent fasting, the types, and the pros and cons, we spoke with registered dietitian Anna Taylor, RD.

What is intermittent fasting?

Intermittent fasting is when you alternate between periods of eating and fasting. This type of eating is often described as fasting “patterns” or “cycles.”

Intermittent fasting isn’t about starving yourself, it’s about reducing your calorie intake for short periods of time. The belief is that your body is satisfied with smaller portions while reducing cravings for unhealthy snacks. That is, as long as you maintain a healthy diet while trying everything.

How does it work ?

There are several effective approaches, but it all comes down to personal preference. “If you want to try intermittent fasting, be prepared to find out what works best for you,” Taylor says. “It might take some trial and error first.”

Some people find it easy to fast for 16 hours and limit eating to just eight hours a day, such as 9 a.m. to 5 p.m., while others struggle and need to shorten their fasting period, Taylor explains.

Types of intermittent fasting

Intermittent fasting is important because you want to maintain adequate nutrition in your overall diet and not take unnecessary risks. “Weight loss is never a one-size-fits-all approach,” Taylor says. “Intermittent fasting may be sustainable for some people, while others find that this approach just isn’t for them.”

If you want to try intermittent fasting, you’ll first need to figure out how you’re going to incorporate this style of eating into your life, especially when it comes to things like social events and staying active, he advises.

Ready to explore your options? Here, Taylor explains some of the most popular intermittent fasting methods.

1. Time-restricted feeding (the 16/8 or 14/10 method)

In this option, you have established fasting and eating windows. For example, you fast for 16 hours a day and can only eat for eight hours a day.

Since most people already fast while they sleep, this method is popular. It is convenient as it extends the overnight fast by skipping breakfast and not eating until lunch. “This form of fasting is a safer bet for many people interested in trying intermittent fasting for the first time,” says Taylor.

Some of the most common ways are:

  • The 16/8 method: Only eat between 10 a.m. and 6 p.m.
  • The 14/10 method: Only eat between 9 a.m. and 7 p.m.

This intermittent fasting method can be repeated as often as you like or even once or twice a week, whatever your personal preference.

Finding the right eating and fasting windows for this method may take a few days, especially if you are very active or wake up hungry for breakfast. But, Taylor says, it’s important that most of the calories are consumed before dark.

“People tend to select higher-calorie, lower-nutrient foods at night. This also gives the opportunity to normalize blood sugar levels while people are most active, before bedtime,” she says.

2. The twice a week method (the 5:2 method)

This approach to intermittent fasting focuses on limiting calories to 500 for two days a week. During the other five days of the week, you maintain a normal, healthy diet.

On fasting days, this approach typically includes a 200-calorie meal and a 300-calorie meal. It’s important to focus on foods rich in fiber and protein to help fill you up and keep calories low during fasting.

You can choose any two fasting days (for example, Tuesday and Thursday) as long as there is a non-fasting day between them. Make sure you eat the same amount of food as you normally would on non-fasting days.

3. Fasting on alternate days

This variation involves “modified” fasting every other day. For example, limit your calories on fasting days to 500, or about 25% of your normal intake. On non-fasting days, resume your normal, healthy diet. (There are also strict variations of this approach that include consuming 0 calories every other day instead of 500.)

An interesting note: One study showed that people who followed this pattern of intermittent fasting for six months had significantly elevated levels of LDL cholesterol (or bad cholesterol) after another six months off the diet.

4. The 24-hour fast (or eat: stop: eat method)

This method involves completely fasting for a full 24 hours. Often it is only done once or twice a week. Most people fast from breakfast to breakfast or lunch to lunch. With this version of intermittent fasting, side effects can be extreme, including fatigue, headaches, irritability, hunger, and low energy.

If you follow this method, you should return to a normal, healthy diet on non-fasting days.

Are there risks?

Intermittent fasting is not safe for some people, including pregnant women, children, people at risk of hypoglycemia, or people with certain chronic illnesses.

“If you are at risk for an eating disorder, you should not try any type of fasting diet,” advises Taylor. “Intermittent fasting is also known to increase the likelihood of binge eating in some people due to restriction.”

If you’re interested in trying intermittent fasting, you should also be aware of some not-so-pleasant side effects. It may be associated with irritability, low energy, persistent hunger, temperature sensitivity, and poor performance at work and activity.

Ultimately, you should contact your healthcare provider and discuss these options. They know your health better than anyone and can offer you the right guidance on whether any of these intermittent fasting options are right for you.