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Have you heard of Intermittent Fasting?

Updated: Apr 8, 2019

By Kathy Napoli, RD, MA

If you are interested in health and wellness then you must have heard about a new strategy for weight loss called Intermittent Fasting. For those who are using it, they think of Intermittent Fasting (IF) as more of a lifestyle and less as a diet plan, since promising research shows that IF may not only help us shed some body fat but also may provide surprising benefits such as improved metabolic health, increased longevity, and protection against many diseases.

What is Intermittent Fasting?

IF involves alternating cycles of fasting and eating. The focus is more on “when you eat” and less on “what you eat.”

Throughout history, our ancestors fasted for various reasons, sometimes for religious reasons, or sometimes out of necessity as food was not always available. During periods of famine, many metabolic processes change to allow our bodies to thrive without food. For example, we see changes in our hormones, genes, and cellular repair processes during fasting periods. The main theory behind the benefits for fasting is that it puts our cells under mild stress, just as exercise stresses our muscles and heart, which ultimately strengthens them.

Recent medical research has demonstrated the benefits of IF:

Increase in energy levels. Improvement in cognition and memory by the increased production of brain neurotropic growth factor, which is a protein that promotes neuron growth and protection. Improvement in insulin and leptin sensitivity, resulting in lower blood sugar levels, and reduced diabetes risk. Enhanced immunity and reduced inflammation for improved cardiovascular health.

There are different methods for IF, all of which split the day into eating periods and fasting periods. Technically, we already fast every day while we sleep.

The most popular methods of Intermittent Fasting are:

The 16/8 Method: fast for 16 hours daily; for example, eating only between 11:00 am

and 7 pm. You eat within an 8-hour period. It can be done for most days of the week.

12/12 Method: fast for 12 hours and eat within a 12-hour period. You can start with a 7 am breakfast, end with a 7 pm dinner, no snacking after dinner.Eat-Stop-Eat: Once or twice per week, nothing is eaten from dinner one day until dinner the next day (24 hour fast).

The 5:2 Method: During 2 days of the week, only 500-600 calories are eaten. The remaining 5 days you eat normally.

The Specifics

Intermittent fasting is not about deprivation, but about dividing your food intake differently than the 3-square-meals-plus-snacks pattern. There is a freedom from counting calories, however, it is advised that you eat healthy meals on your non-fasting periods; you just don’t have to worry about every bite. The key is to not go overboard with your food intake on your non-fasting days.

One of the reasons Americans are overweight is that we eat all day long. Additionally, most of our calories are consumed late in the evening while watching TV, and this type of eating pattern sets us up for weight gain and metabolic dysfunction. IF will prevent that late-night and all-day snacking.

Hunger is the main downside to Intermittent Fasting

Some find it hard to stick with IF because of the hunger factor. But according to recent research, hunger was reported to decrease after 2 weeks with most of the study participants.

Who should not try intermittent fasting as it is not for everyone?

It is not recommended if you have a history of eating disorders, or are underweight. IF should not be used during pregnancy or breastfeeding or when trying to conceive.Those who have problems with blood sugar regulation, or low blood pressure, should consult with their doctor first. However, intermittent fasting does have a good safety profile.


I suggest that you try one of the methods for a few weeks, while keeping a record of how you feel and what you eat. If you don’t like the way you feel, you can switch to another method. Most of my clients like the 16/8 method, and have told me that it isn’t as hard to do as they thought it would be.

Kathy Napoli is a Registered Dietitian (British Dietetic Association) with experience in clinical nutrition. She also has a Masters in Holistic Health Education, and a private nutrition practice called NutraPartners. Kathy teaches workshops throughout the Bay Area, and is a consultant with John Muir Health. Her website is

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