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intermittent fastingWith obesity and overweight rates climbing in the United States, the weight loss industry here was estimated in 2014 to be $64 billion, and surely, that number today has risen.

This is no surprise, and people are constantly seeking all sorts of methods and products to help them shed pounds, from healthy exercise routines to “magic” pills touting too-good-to-be-true weight loss. Healthy and safe options do exist, but unfortunately, there are just as many unhealthy and risky ways to try to slim down.

Intermittent fasting is a method of eating that has become much more popular in the U.S. after gaining a following in the United Kingdom since 2012. There is a lot of information online and in books on intermittent fasting, so we have provided a brief summary of what is intermittent fasting, how it is practiced and potential benefits and challenges.

What is Intermittent Fasting?

Basically, intermittent fasting, also known as intermittent calorie restriction, refers to an eating plan that deliberately alternates between set periods of eating and fasting. Protocols typically fall into either whole-day fasting or time-restricted feeding.

  • Whole-day fasting involves one day of abstaining from food. Alternate day fasting is a 24-hour fast, followed by a 24-hour period of consuming food. Alternate day modified fasting allows for 500-600 calories (or about 20-25% of your regular daily calories) on fasting days. And the 5:2 diet consists of five days per week of eating, and two days of total fasting or modified fasting.
  • Time-restricted feeding (TRF) is eating only during a specified of hours each day, such as eating for only 8 hours per day, and fasting the remaining 16. With this practice, for instance, one would eat from 12 p.m. to 8 p.m., and then fast from 8 p.m. to 12 p.m. the next day. Another type of TRF is eating during a 12-hour window, such as 8 a.m. to 8 p.m., and then fasting the remaining 12 hours. Some practice TRF by eating for four hours and fasting for 20, or by eating one meal per day, followed by 23 hours of fasting.

The main idea behind intermittent fasting is that unlike “standard” diets, you don’t necessarily have to cut calories every day, but only during your established fasting intervals. For some people, this provides a greater sense of control and reduces the feeling of deprivation common in many typical diets.

Plus, intermittent fasting regimens generally are not restricted to specific foods, so you can eat whatever you want, as long as you adhere to the time constraints, and, in the case of modified fasting, to the calorie limits.

Obviously, however, if your goal is weight loss, you should make healthy food choices that will help fill you up and maintain calorie intake within a moderate range. If you’re binging or eating a ton of junk food, even with fasting, your weight loss may be negligible, if any.

Several specific intermittent fasting regimens exist, such as Leangains, Eat Stop Eat, The Warrior Diet, Fat Loss Forever and UpDayDownDay, each with slightly varying methods and recommendations, which can make them easier or harder to follow, depending on your lifestyle and self-discipline.

Why Intermittent Fasting

Intermittent fasting is based on manipulating our physiology. When we eat, our bodies break down food, such as carbohydrates, into sugar for energy. Whatever our cells don’t use for energy is stored as fat. This happens via insulin, which brings sugar into fat cells.

If we don’t eat between meals, insulin levels drop, and our fat cells can release stored sugar for energy. The idea behind intermittent fasting is to decrease insulin levels for a long enough time that we burn fat for energy instead of storing it. That way, we lose weight.

Also, intermittent fasting increases human growth hormone levels, which benefits fat loss and muscle gain, along with the fat-burning hormone, norepinephrine.

Intermittent fasting protocols are still being researched, but initial results have been promising for weight loss among the obese and overweight populations. Those practicing intermittent fasting tend to lose more weight and body fat and remain more compliant than individuals who are following a traditional restricted calorie regimen.

One 2014 review study found that this eating pattern can stimulate a 3–8% weight loss over 3–24 weeks. Plus, intermittent fasting has been shown to improve brain health, bolster stress resistance and reduce inflammation.

Studies also have shown that calorie restriction by 30-40 percent can extend life span by a third or more, as well as reduce risk of many common diseases, such as cancer, Type 2 diabetes and heart disease.

Challenges and Risks

Note that research on intermittent fasting is still in its early stages, and some studies have been small and/or short-term. So there is definitely more to learn about how this way of eating ultimately impacts one’s health.

Also keep in mind that intermittent fasting is not recommended for children, pregnant and breastfeeding women or people with dietary restrictions, eating disorders or diabetes. If you have diagnosed medical conditions, take medications, are trying to conceive, or if you’re simply not sure, see your doctor before embarking on this way of eating.

And if you try intermittent fasting, be aware of common side effects:

  1. Hunger – This is very common, but is said to subside as your body adapts to the new eating-fasting cycle.
  2. Weakness – You may feel weak on fasting days, and it may be challenging to exercise at your typical intensity. Again, this should improve as you adjust to the eating patterns.
  3. Impaired athletic performance – You will have to time workouts to correspond with being fueled and having the energy to push yourself.
  4. Irritability, brain fog and headaches – You may not feel well when calorie-deprived. Make sure you stay properly hydrated to help minimize these symptoms.
  5. Amenorrhea and infertility – Loss of menstruation and infertility are potential risks for women.
  6. Difficult to sustain – This strict regime can be challenging to maintain over time, with travel, work obligations, vacations and holidays interrupting your daily routine. You may do intermittent fasting for a period of time, then take a break before returning to it.

The Bottom Line

Just like any diet, intermittent fasting has some benefits and risks. It’s not for everyone, but may be worth a try if you are seeking to shed a few pounds. Choose a method that works best for you, start gradually and change protocols if necessary. Ultimately, this should not be so difficult to follow that it severely interferes with your lifestyle.

According to Harvard Health Publishing, here are some safe, sustainable ways to maintain or lose weight, as a modified way of intermittent fasting:

  1. Avoid sugars and refined grains. Instead, eat fruits, vegetables, beans, lentils, whole grains, lean proteins and healthy fats.
  2. Let your body burn fat between meals. Don’t snack. Be active throughout each day and exercise regularly.
  3. Consider a simple form of intermittent fasting. Limit the hours when you eat, and for best effect, aim for earlier in the day (between 7 a.m. to 3 p.m., or even 10 a.m. to 6 p.m., but not in the evening before bed).
  4. Avoid snacking or eating at nighttime, all the time.