- Intermittent fasting is a type of dieting where people fast during a portion of the week and then eat on the other days.
- The 5:2 intermittent fasting diet is one of the better-known plans, allowing people to eat what they want 5 days a week and limiting calories on the other 2 days.
- Researchers say people on the 5:2 plan lose about as much weight as on traditional diets, but people on the 5:2 schedule tend to stick with their diet longer.
- Experts say there are a number of health benefits to intermittent fasting, but there can be side effects. They add there are some groups, including people under 18 and pregnant people, who should not do intermittent fasting.
Intermittent fasting is a diet plan that switches between fasting and regularly eating.
It works by prolonging the time between eating, so your body finishes burning calories and then begins to burn fat.
This type of eating not only helps you manage your weight but can prevent or even reverse some forms of disease. Experts say many people find intermittent eating more manageable and might stick with it longer than traditional dieting.
“While some people use it to lose weight, the biggest benefit is that intermittent fasting seems to help stabilize insulin levels,” said Dr. Mahmud Kara, the founder of KaraMD, a website promoting functional medicine.
“When you don’t eat, your body doesn’t have carbohydrates to break down. If there are no carbohydrates, there is no glucose in your blood. And if there is no elevated blood glucose, there is no need for your pancreas to send out insulin,” he said.
“Intermittent fasting gives your pancreas a break and allows your body the opportunity to balance itself back out,” Kara said. “Make sure you consider how much you are eating. It’s easy to eat too little (or too much).”
One of the better-known intermittent fasting diets is the 5:2 plan.
Under this plan, you eat what you want for 5 days each week and then limit yourself to 500 calories on the other 2 days.
In a recent study conducted at Queen Mary University of London, researchers said the results of 5:2 intermittent fasting are similar in effectiveness to traditional dieting.
They also found, however, that people generally preferred intermittent fasting and were more willing to stick with it.
The study included 300 adults with obesity — 100 received information on conventional dieting, 100 received information on intermittent fasting, and 100 received information on intermittent fasting along with 6 weeks of support.
The researchers followed participants for a year, noting weight loss. At the end of the study, they noted:
- Fifteen percent of participants in the group provided with information on traditional dieting lost at least 5 percent of their body weight.
- Eighteen percent of people given information on intermittent fasting lost at least 5 percent of their body weight.
- Twenty-eight percent of people who received information on intermittent fasting as well as 6 weeks of support lost at least 5 percent of their body weight.
While weight loss was similar in the groups, the number of people who lost weight increased with intermittent fasting.
Researchers said the two groups who used the 5:2 diet had a more positive experience than people using the traditional diet.
This could be an essential factor for doctors recommending weight loss and weight management programs because they might be more likely to remain committed to the diet.
“The best news is that there is no one-way to do it,” Kara said. “Depending on your schedule, personality, and lifestyle, you can pick a fasting protocol that best suits your needs.”
“No matter which type you choose, it’s important to remember to eat healthy foods during your chosen eating window,” he said. “These fasts won’t work if you choose meals that are full of processed foods.”
Besides the 5:2 plan, other types of intermittent fasting diets include:
- 16:8. This type of intermittent fasting involves eating only during a specific 8-hour period each day.
- Eat Stop Eat. It involves fasting for 24 hours twice a week. It’s similar to the 5:2, but the fasting days are intermingled — eat one day, then fast the next day, then eat again before fasting another day, and so on.
- The Warrior Diet. This diet involves 20 hours of undereating, followed by 4 hours of unlimited intake, usually eating a large meal in the evening.
- Skipping meals spontaneously. This is when you can occasionally skip meals. You can take advantage of intermittent fasting based on your needs, such as skipping meals when you aren’t hungry instead of eating because it is mealtime.
There are numerous health benefits of intermittent fasting.
“Intermittent fasting can lower cholesterol, reduce liver fat, enhance glucose management, and improve blood pressure, in addition to reducing body weight. Enhanced motor coordination, enhanced endurance, and better sleep have also been linked to intermittent fasting,” Shauna Hatcher, MSPH, a certified nutritionist at The National Wellness and Public Health Network, told Healthline.
It can also lead to a longer life, a sharper mind, and protect against type 2 diabetes, heart disease, neurodegenerative disorders caused by age, inflammatory bowel disease, and some types of cancer.
“It can take 2 to 4 weeks for your body to adjust to your new way of eating. During this time, you might experience headaches,” said Hatcher.
“Other possible side effects include digestive issues, such as nausea, diarrhea, constipation, and bloating. Low blood sugar caused by intermittent fasting might make you tired and weak. You might notice sleep disruptions, resulting in fatigue during the day,” she said.
Experts say there are some groups of people who should not participate in intermittent fasting:
- children and teens under 18 years old
- people who are pregnant or chestfeeding
- people with diabetes or blood sugar concerns
- people with a history of eating disorders
“As helpful as intermittent fasting is, it’s not for everyone,” said Kara. “If you have a history of eating disorders or are taking medication that cannot be taken on an empty stomach, be sure to talk with your doctor or nutritionist before starting. The type of food you eat is equally, if not more important, than the time of day or hours you consume the food.”