Intermittent fasting: Does it work, and is it safe?

Intermittent fasting is an eating plan that focuses on when you eat, rather than what you eat.

The concept is pretty simple. You set a window of time during which you can eat each day, and you fast the rest of the time. This is claimed to be an effective way to manage your weight. Is the claim true?

The answer is yes, it can be an effective approach to weight management, according to Jessica Bishop, a dietetic intern at OSF HealthCare. However, this newly popular approach is not a magical cure that will work for everyone. Studies show a success rate for intermittent fasting that is about the same as other diets.

“A lot of people have found it effective, but it’s very personalized,” Jessica said. “It’s not across-the-board successful. Like most diets, the effectiveness is based on how well the plan fits the individual.

“This diet essentially restricts calories, leading to weight loss. But in the end it is no better for us or more successful than a well-balanced, calorie-restricted diet.”

How it works

Experts are still conducting research on intermittent fasting. But some evidence suggests that it may be beneficial to give your digestive system a regular break from processing the food you eat.

Research suggests there is a sort of “metabolic switch” that gets flipped when your body knows to start converting stored fat into energy because no food will be coming for a while.

There are variations of intermittent fasting, and nearly endless options to personalize it to your preference. Most people tend to do what is called the 16/8 approach, in which you have an eight-hour window each day to eat, and you fast for 16 hours per day from all food and any beverages with calories.

empty dinner plate and plate with food. Clock in the middle

In one variation of intermittent fasting, called 5/2, people choose two days per week when they only eat a single small meal while eating regularly the other five days of the week.

So, you can pick the eating and fasting windows that work best for you. You can pick how you schedule your meals during your eating window. You can pick what you eat and how much. And you can pick for how long you follow the plan, as well as how tightly you follow the plan. Think the plan is more sustainable if you give yourself a cheat day where you eat regularly once or twice a week? Go for it.

A risk with fasting, according to Jessica, can be the danger of nutrient deficiency. The danger is not so severe with the 16/8 approach, but if you are fasting for two to three days at a time, the risk is concerning.

“I would recommend something like the 16/8 approach over the other methods if you choose to try intermittent fasting, because you are still eating something each day. It’s more balanced,” Jessica said.

Keep it healthy

Whether or not you try intermittent fasting, you need to be mindful of what you eat. One of the biggest draws of intermittent fasting – the lack of dietary restrictions – can also be one of its weaknesses.

“You can’t eat until you’re stuffed for your entire eating window,” Jessica said. “You need to eat healthy foods, nutrient-dense foods. Whole grains, protein, fruits, vegetables and dairy. Hit those food groups so you’re not putting yourself at risk for nutrient deficiencies.”

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You also need to stay hydrated while you fast, so drink a lot of water.

Jessica said the science is still relatively new for intermittent fasting, and a lot of research is still being conducted to identify and verify any health benefits, risks and long-term effects. As it stands now, the current evidence supports intermittent fasting as a weight loss method for up to 12 months.

Some people are also probably not right for intermittent fasting. It’s not recommended for anyone who is pregnant, has diabetes or is under 18. Jessica doesn’t recommend it for anyone with a history of eating disorders, either, because fasting could serve as a trigger for a disorder.

Consult your doctor

Just like with any new weight loss regimen, the safest approach starts with a visit to your primary care physician. You need to find out from your doctor if you’re healthy enough to start a weight loss approach, what the risks are and how to do it safely.

Being a healthy weight can reduce risk factors for several health conditions, including high blood pressure, high cholesterol, heart disease, stroke, osteoarthritis and Type 2 diabetes.

“The most important thing to remember is weight loss isn’t one-size-fits-all. Finding something that works for you is the key,” Jessica said. “Overall, we typically recommend just having a healthy lifestyle that includes a healthy dietary pattern and being physically active.”

About Author: Ken Harris

Ken Harris is the proudest father and a writing coordinator for the Marketing & Communications division of OSF HealthCare.

He has a bachelor's in journalism from the University of Wisconsin-Madison and worked as a daily newspaper reporter for four years before leaving the field and eventually finding his way to OSF HealthCare.

In his free time, Ken likes reading, fly fishing, hanging out with his dog and generally pestering his lovely, patient wife.

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Categories: Diet & Exercise