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Everything you need to know about the 16:8 principle — the most common form of intermittent fasting

food eating food eating
It's a type of intermittent fasting.
AP/Brandon Wade
  • The 16:8 principle is also known as intermittent fasting, which consists of a 16 hour fast and an eight-hour feasting period.
  • You can eat whatever you want during the eight-hour feasting window, but dietitians recommend eating pure and nutrient dense foods to make the most of your fast.
  • You'll want to make sure you are getting enough calories when observing the 16:8 principle, as not consuming enough can be problematic to your body.
  • But like any new eating plan you may try, it's important to observe the 16:8 principle under the guidance of a trained professional.

Much like the keto diet, intermittent fasting is definitely something that has gotten major buzz this past year, as many health professionals are recommending this fasting approach which is said to help lower blood pressure and reduce inflammation in the body.

Intermittent fasting, according to registered dietitian Jackie Arnett Elnahar, RD, is also often called the 16:8 principle, as she explained that it usually consists of a 16 hour fast with a remaining eight-hour feasting period. though there are many forms of intermittent fasting, this is one of the most common.

However, Elnahar explained that it's important to not look at the 16:8 approach as a diet, as she said it's really more of a wellness tool which can be used to improve your health.

"By incorporating the 16:8 principle into your lifestyle, you are able to tap into the many clinically validated benefits of intermittent fasting such as reduced inflammation, better insulin control, increased energy, lower blood pressure, and weight loss," Elnahar told INSIDER. "It is a more manageable and realistic way to gain the benefits of intermittent fasting than the more evasive way of every other day fasting or fasting for a whole day.

To give you a closer look at the 16:8 principle, we spoke more Elnahar and other professionals about some things you'll want to keep in mind if you're looking to give fasting a try. Below are some of the things they recommend keeping in mind.

You can eat whatever you want when observing the 16:8 principle, but you'll want to be careful not to eat badly.

bananas eating banana
Try to avoid processed and fried foods.
Aaron Favila/AP
Although you can practically eat anything you want during the eight hour feasting period, Elnahar said it's wise to pay attention to the food you are putting into your body. You won't want to eat processed, fried, or sugar-heavy foods while fasting, she explained. Instead, she encouraged eating pure and nutrient dense foods while doing the 16:8 approach. That means consuming nutrient-rich vegetables, lean and organic protein sources, minimal sugar, and high fiber carbohydrate sources, she suggested.

You'll also want to make sure you get enough calories.

Managing your calorie intake is equally important when observing the 16:8 principle, as Elnahar said not consuming enough calories during your fast can be problematic to your body.

"It is very important to get enough calories so your body doesn't trigger a metabolic starvation state and starts storing fat instead," Elnahar told INSIDER. "You need to make sure you are eating nutrient dense fats to maintain homeostasis in the body especially for optimal hormone production," she said.

There is no regret or guilt attached to the 16:8 principle.

Instead of the restrictive calorie and carb counting approach associated with some diets, board-certified cardiologist Dr. Luiza Petre, MD, said there is no regret or guilt associated with the 16:8 principle, as it's not based on deprivation.

"People rebound and feel frustrated when they are restricted all the time, and with 16:8, that isn't an issue," she said.

The 16:8 principle is very flexible and can be combined with any diet you are observing.

Vegan Dinner
It's compatible with many diets.
Donald Bowers/GettyImages
Dr. Petre also lauded the flexibility of the 16:8 principle, as she said it's flexible enough to be overlapped with any other diet (protein ketogenic, vegetarian, Mediterranean or DASH diet) of your choosing.

The 16:8 principle is also sustainable.

Sustainability is another one of the perks of fasting, as Dr. Petre suggested that it is something people can stick with easily. "Nine out of 10 dieters put the weight back on, just because the diets they try are not sustainable for life," she explained to INSIDER.

You'll want to incorporate healthy fats into your diet.

Eating right on the 16:8 principle also means incorporating healthy fats into your diet, according to Dr. Petre. "Healthy fats help reduce inflammation, improve insulin sensitivity, and help support a healthy metabolism," she said. "Omega-3 found in healthy fats helps support thyroid hormone function, which regulates body fat."

You'll also want to go easy on the carbs if you are giving the 16:8 principle a try.

loaves of bread
You may want to avoid bread.
Daniel Berehulak/GettyImages
Dr. Petre also advised approaching simple carbs with caution when observing the 16:8 principle, as she said carbohydrates are calorie dense and can cause cravings. "Try to avoid pasta, bread, cereal, rice, potatoes, and fruit juices," she recommended.

It's important to have guidance from a professional.

Although observing the 16:8 principle may have positive effects on your health, Dr. Petre said you should seek guidance from a professional as a medically supervised program can help monitor your health and overall progress.

You'll always want to stay hydrated while fasting.

Eating nutrient-dense foods is important while fasting, but Dr. Carrie Burrows, PhD, says it's equally crucial to make sure you are drinking enough water during your fasting window. Even though you may be cutting back on food intake, she said you won't want to cut back on your overall fluid consumption. Doing so can be dangerous to your body, she added.

But it's important not to overdo it at the gym while fasting.

"If you are not used to working out on an empty stomach, then ease into your workout routine or vary the time you workout," Dr. Burrows told INSIDER. "Don't push yourself; if you are not feeling well, you won't want to overdo it," she said.

Visit INSIDER's homepage for more.


SEE ALSO: Everything you need to know about 'intermittent fasting' — the buzzy diet that won't make you change what you eat

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