• Dr. Lena Fernandez

Is Intermittent Fasting Right For You?

Updated: May 23


Photo by Massimo Rinaldi on Unsplash


I've been getting a ton of questions about intermittent fasting (IF) so I thought I provide you with the latest news on IF – whether you are thinking to get started with IF or are already following this way of eating.

Recent studies show that 3 days fast can boost the immune system, help with weight loss, better cardiovascular health, improve endurance, lower blood pressure, and reduce inflammation. A more recent data, which I'll get to in a minute, shows that you might not have to fast nearly that long to get these benefits.

In a 2014 study, Valter Longo, and colleagues at USC found that fasting lowered white blood cell counts, which in turn triggered the immune system to start producing new white blood cells. White blood cells (or lymphocytes) are a key component of your body’s immune system. Once you start eating again, according to Longo, your stem cells kick back into high gear to replenish the cells that were recycled.

The idea behind this strategy is that you have to fast for several days to get the benefits: basically, you have to fully deplete your energy reserves (in the form of glycogen), and it takes your body at least 24 hours, and probably 48 hours or more, to do this. The good news is that you probably only need to fast once or twice a year to gain the benefits that Longo described. However, I highly encourage you to get professional help if you decide to fast for more than 24 hours.

It turns out that you can get many of the benefits of fasting without doing a 3-day fast, which for most people is really, really difficult to accomplish without causing organ injuries. Instead, you can try a much easier type of fasting, called "time-restricted" fasting. With this strategy, you fast every day, by eating all of your food in a 6-hour or 8-hour window.

Intermittent Fasting (IF) in the last decade has been quite popular and you've probably heard about it from your friends or from your personal trainer at the gym. But, many don't quite understand what intermittent fasting is all about.

So, I'm specifically going to discuss what intermittent fasting (IF) is, types of intermittent fasting schedules (there are several), and who it is, and isn't good for especially since most likely you know someone who's been raving about IF.

What is intermittent fasting?

We are technically all fasting from our last meal in the evening, until our first meal the following day… There's nothing too sexy about intermittent fasting, it's just a special pattern of eating.

Simply put, intermittent fasting is the process of alternating between a narrow window of consuming food, and an extended period of not eating.

If you really think about it, most likely you have done a moderate length fast in the past when you forgot to eat breakfast and then all the sudden you realized it's the middle of the afternoon and you're just barely having your first meal... congrats, you've been fasting.

If you can imagine waiting 16 or 18 hours before eating again or going through an entire day without breakfast, lunch, or dinner. That’s essentially what people do who are currently following intermittent fasting on a regular basis.

This pattern of eating leads to significant calorie reduction, hence weight loss or improved overall health if done correctly.

What happens to our body when we eat?

At a deeper level, whenever we eat, the body releases insulin to help cells convert sugars (in particular glucose) from food into energy. If the glucose isn’t used immediately, insulin helps make sure the excess is stored in fat cells.

And when you eat the wrong foods at the wrong times, your blood sugars are constantly high, which increases insulin levels. This cycle of high sugar and insulin levels is the main cause of type 2 diabetes, a huge epidemic in America.

In addition, high blood sugar causes damage to blood vessels such as arteries. The kidneys are getting clogged up, and the reason people end up in dialysis.

Dr. Mark Hyman, indicates in his book What the Heck Should I Eat? that the average American consumes 152 pounds of sugar and about 133 pounds of flour, which convert to sugar. Altogether, that’s more than three-quarters of a pound of sugar and flour for every American daily, which Hyman calls “a pharmacologic dose our bodies were not designed to handle.”

Indeed sugar's impact on your health and the immune system is a complex interplay of hormonal, metabolic, and immunologic processes that can severely threaten human health. And some of that impact is immediate. Refined sugar can reduce how white blood cells perform and increase inflammatory markers. In fact, studies show that carrying even five extra pounds cause fewer white blood cells with a reduced capability to fight infection.

However, when we avoid sugar and go without food for extended periods, as people do during intermittent fasting (IF), insulin is not released, the body then turns to break down fat cells for energy instead.

Right now you're probably giving intermittent fasting (IF) a try yourself to:

  • Lose weight

  • Detox your systems

  • Increase energy

  • A medical condition (you think you have)

  • Religious purpose

  • Everyone is doing it, so why not me?

The most important thing you must understand is that intermittent fasting isn't risk-free.

What are the risks and side effects of intermittent fasting?

  • Dehydration is the most common side effect clinically seen among my patients who've been following intermittent fasting on their own for more than 30 days.

  • Muscle wasting is also a common side effect mainly from breaking the fast with high carb, high sugar, and low protein and fats.

  • Overeating during the eating window

  • You most likely feel hungry all the time, which is affecting your mood and concentration.

  • You might have a headache or feel tired

  • Feeling irritable during a fasting state

  • You drink alcohol during IF days (don't do it) :)

Is intermittent fasting (IF) the right for your body?

No diet is good or bad until we understand the root cause of your health struggles first. This is the reason why I evaluate gut health in all of my patients before trying any specific diet plan since there's no one single diet plan that fits all.

It is especially important to check the following inflammatory markers prior to and during intermittent fasting to make sure your body can handle this type of eating pattern.

1. Insulin levels

2. IGF-1 (insulin growth factor-1) marker

3. Leptin (hormone stored in your fat cells)

4. Growth hormones (if too low, that means muscle loss)

5. Throughout the day cortisol level (we don't want dips or spikes)

6. Lipids/cholesterol (if LDL is too high it means your liver is clogged up) eventually this will cause heart problems, gallbladder and kidney stones among other health problems.

7. Kidney filtration rate to evaluate hydration level

And there are several known contraindications to intermittent fasting (IF):

  • Pregnancy

  • Diabetes

  • Kidney disease

  • Heart disease

  • Taking certain medications

  • Eating disorder

  • Drop-in blood pressure

  • Overload of toxins

  • Lack of nutrients and cofactors

  • Muscle breakdown

  • Sleep disturbances

  • Severe adrenal/thyroid fatigue: IF is associated with a decline in T3 and a rise in reverse T3, which can cause low thyroid

  • Women who are trying to get pregnant


Do's and Don'ts of intermittent fasting

Do's this during intermittent fasting:

  • Double water intake on fasting days; sometimes hunger is a thirst

  • Rest more during intermittent fasting (IF) state

  • Keep fasting period short (don't IF for more than 30 days at a time

  • Go for light walks and practice meditation

  • Caution with extraneous exercise during fasting

  • Get enough protein from plants and fats especially on non-fasting days

  • Eat dinner early, STOP eating four hours before bed

  • Eat at approximately the same times each day

  • Consider hormones, men vs women

  • Consider benefits vs risk

  • Continue medications and supplements

  • Consider toxin mobilization (i.e. EDTA or Glutathione) intravenous therapy to eliminate toxins effectively for best health outcome.

Don't do this during intermittent fasting:

  • Excessive workout

  • Break a fast with a feast

  • Fast if you feel too tired or not well

  • Mentally/emotionally unstable

How to get started with intermittent fasting

First, start with time restriction eating the night before i.e. eat an early dinner preferably 3 to 4 hours prior to bedtime, do this for 30 days then introduce an intermittent fasting schedule that suits your needs, which I'm going to discuss types of IF shortly.


You must understand that the transition can be challenging when you first try intermittent fasting (IF).

It's not uncommon to feel uncomfortable, and even severe hunger as you abstain from food, so take it slow and try different kinds of intermittent fasting to see what works the best with your health goals and routine.

You may also notice your stomach grumbling or feel a sense of emptiness during the first week or two of intermittent fasting (IF). Some people are exhausted, lightheaded, or shaky from low blood sugar on fasting days (this happened to me and it wasn't a fun experience) :(

Poor concentration, irritability, mood swings, and even dizziness can occur during IF state.

If any of the above side effects occur you should consult with a healthcare professional and be sure to stay hydrated and get plenty of rest.

Once again, I encourage you to first try eating early dinner and then narrowing the feeding window from an initial unrestricted period from down to 12 hours, then 10 hours, then eight hours before finding a feeding window that is sustainable.

Why you should give intermittent fasting a try

Studies show periodic fasting has direct effects on gut health and may be beneficial to:

  • Increase good bacteria and improve the immune system

  • Lose weight

  • Stabilized blood sugar

  • Reduce inflammation

  • Increase oxygen level

  • Improvements in memory and stress resistance

  • Slowed aging process

  • Longer lifespan

In fact, animals and some human data suggest that IF may bring about a greater reduction in hepatic (liver) and visceral (organ) fat stores, insulin-like growth factor 1 (IGF-1) levels, and cell degeneration, and increased insulin sensitivity and adiponectin levels for more optimal health.

What fasting schedule works best for you?

There are different types of intermittent fasting (IF):

  • Alternate day fasting (ADF): consists of a "fast day" (25%-100% energy restriction) alternating with a "feed day"

  • Intermittent fasting (IF): 5:2, two non-consecutive days a week, only eat between 500-600 calories. Eat normal calories the other days a week.

  • Time-restricted eating (TRE): eat only during a set 8-hour window of time during the day ending four hours before bed. This is called an 8:16 diet.

  • Short-term periodic (ST) or prolonged fasting (PF): both require zero food intake. ST less than 3 days and PF greater than 3 days. This type of eating is known as a water fast.

I've seen intermittent fasting clinically to work well especially for weight loss, reverse type 2 diabetes, reduce cholesterol levels, boost metabolism, eliminate pain, increase energy, and build muscle for a stronger and healthier body.

Keep in mind, intermittent fasting is NOT a long term diet for anyone.

The simple and proper diet with healthy fats, moderate protein, and low carb intake can take your health to the next level, which you can simply follow indefinitely.

Be sure to avoid empty nutrient and toxic foods such as:

  • Refined carbohydrates (sugars, grains, and starches)

  • Refined oils (vegetable oil, soybean oil, canola oil or corn oil)

Any lifestyle changes require you to set the intention, stay focused, and make planning simple.

To understand exactly what healthy intermittent fasting should look like just CLICK HERE to watch my video where I walk you through the step by step process on how to get started with IF for the best health outcome.


Comment #replay when you watch my video so I can hop in there to answer your questions and give you a big shout out.


Much love,

Dr. Lena Fernandez

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