Dr. James Kelley On Everything You Need to Know About Intermittent Fasting

Have you ever considered intermittent fasting?

It's not a diet by any means, but it is a lifestyle a lot of people have chosen to adapt. We were curious to learn more, so we reached out to Dr. James Kelley, MD and guru when it comes to intermittent fasting. As the medical science liaison for L Nutra and creator of Fast Bar and Pro Lon, he knows exactly what he's talking about.

Keep reading for our full interview with Dr. James Kelley, in which he reveals everything you need to know about intermittent fasting.

Sweety High: What exactly is intermittent fasting?

Dr. James Kelley: Intermittent fasting (IF) is the use of various meal timing schedules that utilize intervals of fasting and eating. While there are a variety of fasting methods within the practice IF, they all share the same primary approach that alternates between intervals of eating and fasting. During an intermittent fast, a person will fast for a period of time during the day or week and then return to a preferably healthy diet for the non-fasting portion of the day or week. Some more-common methods of intermittent fasting include Time-Restricted Eating (TRE), Alternate Day Fasting (ADF), and the 5:2 Diet. TRE is the most popular form of intermittent fasting now being practiced where eating is limited to a certain number of hours each day, typically 8 or 12 hours.

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SH: At what age is it safe to start intermittent fasting?

DJK: That really depends on someone's overall health, weight management goals and doctor's directions. While there are some studies that have evaluated the impact of intermittent fasting in those over the age of 18, it is not currently recommended for individuals in periods of rapid growth, such as children or adolescents. There is also some debate about exposing teenagers and younger adults to diets that may contribute to eating disorders. Once you've reached peak physical maturity, however, the risks to intermittent fasting appear to lessen when done correctly. The American Heart Association states that intermittent fasting may produce weight loss, reduce insulin resistance and lower the risk of cardiometabolic diseases, although its long-term sustainability is unknown. A 2019 review in the New England Journal of Medicine (NEJM) concluded that intermittent fasting may help with obesity, insulin resistance, dyslipidemia, hypertension and inflammation.


SH: What hours of the day do people typically eat while intermittent fasting?

DJK: Usually those practicing IF start to fast by the evening and do it through the morning. They may use IF to break bad habits of snacking late. These eating or fasting "windows" help your body to burn fat for fuel. The most popular versions of Time-Restricted Eating (TRE) are the circadian 12:12 and 16:8 diet, which typically involve fasting overnight from 8 p.m. until 8 a.m. or 12 p.m. the following day, respectively.


SH: Are there specific foods that are recommended or should be avoided while intermittent fasting?

DJK: IF is less about which foods to avoid and more about timing. I recommend eating healthy while practicing IF. If weight management is your goal, look for foods that support your goal. I also recommend plenty of water during your fast. Coffee, tea and other non-caloric beverages are also permitted while practicing IF. Though intermittent fasting is recommended for weight loss and positive changes to your body, it is not a diet—no macronutrients (carbs, proteins, fats) are counted, no foods are "legal" or "illegal" and the IF lifestyle is intended to be a lifestyle.

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SH: What is autophagy? Why is it associated with intermittent fasting?

DJK: Autophagy is how the body cleanses itself of damaged cells so it can regenerate newer, healthier cells. "Auto" means self and "phagy" means eat. Autophagy removes debris and gives the body power to self-regulate back to optimal smooth function. It's like hitting a reset button. However, research into autophagy in humans is still somewhat limited, and it is extremely difficult to measure. While many Intermittent Fasting advocates believe that Autophagy is a potential benefit, the general consensus among scientists and experts is that in humans it likely does not begin until about 24 hours into a fast, and peaks between 48 and 72 hours. Any fast beyond 24 hours is considered a prolonged fast, and should only be considered after discussing with your healthcare provider.


SH: What happens if you eat outside the allotted time window?

DJK: If you are practicing IF and eat outside of the allotted time window, you've broken your fast. You can get right back to it but the fast restarts. Hunger is a common challenge to fasting, which is why L-Nutra created Fast Bar, which is scientifically formulated to support IF. Fast Bar helps curb hunger, yet does not break your fast. It's a way to hack your fast.


SH: Are there any safety guidelines when it comes to intermittent fasting?

DJK: With IF, you want to avoid long periods of fasting and get into a rhythm of fasting and eating intervals. Drink plenty of water. Pay attention to how you feel. Check with your doctor if you have questions about how IF fits into your overall health.


SH: Is there anything you'd like to add?

DJK: Remember that IF is not a diet. It's a lifestyle. You can personalize it to your schedule as long as you follow the core practices. Eat healthy. Drink plenty of water. Get quality sleep. Use Fast Bar to manage hunger. And reap the rewards of the IF lifestyle.

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