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Intermittent Fasting 101

Kathryn-Parker-aviv-clinics by Kathryn Parker , RD, LD/N, Dietitian
May 25, 2022
mature woman drinking a healthy green smoothie

Intermittent fasting has been on an increasing number of peoples’ radars over the past 5 to 10 years. Yet, it’s not a “new” concept. In prehistoric times, fasting was just a part of daily life. As hunters and gatherers, our ancestors went days without nourishment.

The documentation of intermittent fasting dates back to the 1500s, recorded by Luigi Cornaro, a nobleman. Cornaro made significant changes to his diet and lifestyle habits in his 40s to strengthen his “weak constitution.”

At age 83, his colleagues urged him to chronicle these changes—because they had known him as a younger man and were certain Cornaro should not still be living. He continued to beat the perceived odds and lived another 20 years, dying at age 103.

Fast forward to 2019, when the New England Journal of Medicine published a peer-reviewed paper on the health benefits of intermittent fasting. Intermittent fasting remains a viable approach to living longer, healthier lives.

Clock and time

How Does Intermittent Fasting Work?

The human body operates with one goal in mind: survival. If you go 8-12 hours without food, your entire body is out of gasoline. You have no more stored glycogen, which provides energy. Your liver and muscle cells are empty, and your brain is screaming for sustenance. As a result, your body taps into what’s easiest to access in order to feed the brain: visceral fat.

It’s important to note that not all fat stored in the body is “bad.” Humans need certain types of fat to promote healthy metabolism and optimal hormone levels.

Visceral fat is not that type. High visceral fat levels may contribute to diabetes, heart disease, stroke, artery disease, and even cancer. So, reducing those levels is not just about eliminating a spare tire or muffin top.

Scientific Benefits of Intermittent Fasting

The research on intermittent fasting reveals its impact beyond weight loss. Thirteen hours without ingesting calories prevents breast cancer in both women and men. In rats, a 14-16 hour fasting period improves longevity by 30-50%.

Additional benefits include improvements to:

  • thinking and memory
  • blood pressure
  • physical performance
  • type-2 diabetes
  • sleep apnea

 

Intermittent fasting also helps with reducing inflammation.
Too much inflammation in the body can lead to conditions such as:

  • Alzheimer’s disease
  • arthritis
  • asthma
  • multiple sclerosis
  • stroke

 

mature woman pours her drink

The Simplest Diet: Intermittent Fasting

Aside from the health benefits, one of the best aspects of intermittent fasting is that it doesn’t require people to invest any extra time or money. You don’t have to buy special foods or spend hours measuring and weighing your meals. There are also no “off-limit” foods. You can still enjoy your favorite meals and snacks as long as you do so in moderation.

All intermittent fasting requires is knowing what time it is.
And, in truth, we all fast—it’s called sleeping!

The goal is getting to the sweet spot, the thirteen-hour marker of fasting, where the medical benefits take hold. However, there’s no detriment to switching up your schedule. Some days you may hit 13 hours, other days, you might aim for 16 or 18. A popular intermittent fasting schedule is 16:8—fasting for 16 hours and feasting for eight. On the weekends, you may decide not to stick to a schedule. Consistently practicing intermittent fasting is most important.

That said, there is some risk in fasting for too long. For example, if you’re regularly hitting the 20-hour mark, you’ll likely start to lose muscle mass. The body can only absorb 30 grams of protein at a time. With a limited feast window, you may not be getting adequate protein intake.

Are There Any Risks Associated with Intermittent Fasting?

Individuals living with diabetes should consult with their endocrinologist or diabetes educator before commencing with intermittent fasting. However, if someone is only in the stage of insulin resistance, intermittent fasting can prevent diabetes from developing.

Some people report experiencing digestive issues, such as constipation. In this case, they’re likely not drinking adequate amounts of water or eating enough high-fiber foods. Of course, in the initial stages, one might experience some fatigue, hunger pangs, and possibly headaches. As with any lifestyle change, it takes persistence and time to adapt. Still, it’s critical to have a conversation with your healthcare provider if you’re curious about intermittent fasting’s effects.

Ready to Explore Intermittent Fasting?

Different types of intermittent fasting exist. Some of the most common include:

Time-Restricted Fasting. This approach works by limiting the daily window of feasting. For example, if you eat your first meal of the day at 10 a.m. and your last meal at 6 p.m., you’ve followed the 16:8 plan. Common ratios for time-restricted fasting include 14:10, 16:8, and 18:6.

5:2 fasting. In this strategy, individuals eat “normally” five days a week and fast for two days. On the fasting days, they restrict their calorie intake to one 500-calorie meal for women and one 600-calorie meal for men.

Alternate Day Fasting. Using the same calorie intake as 5:2, fasting takes place every other day.

Time-restricted fasting is a great way to start because you can ease into it—gradually shrinking your feast window. As you get more accustomed to fasting, you might venture into other methods to see if they work for you.

Bottom Line

The benefits of intermittent fasting are well-documented. Whether you’re looking to lose weight, improve your daily performance, optimize your cognitive health, or generally extend your lifespan, intermittent fasting is effective.

Nutrition is a core component of the Aviv Medical Program. If you’d like to learn how the program works and its benefits, contact us for more information.

Aviv Medical Program provides you with a unique opportunity to invest in your health while you age.

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