Fasting vs. Calorie Restriction

Fasting and calorie restriction essentially sound like the same thing don’t they?

You don’t eat when you fast, so that’s a restriction of calories, right? Hmm…there’s a little bit more to that story.

First of all, let’s define FASTING:

The abstinence of food and drink for a specific period of time.

This means NO calories, it doesn’t mean LOW calories.

The benefits of fasting include:

  • Promotes autophagy – the cellar self-cleansing process that breaks down and recycles damaged cells
  • Normalizes insulin sensitivity 
  • Promotes the secretion of human growth hormone (HGH), which has been used to treat obesity, help build muscle mass and burn fat
  • Helps normalize ghrelin (your hunger hormone) levels and keep you more in tune with real hunger signals
  • Help give your gut a break from continuously digesting food

While fasting is often used as a weight loss tool, it is important to keep in mind that fasting is NOT a diet. It is NOT the same as STARVING YOURSELF.

When we talk about fasting protocols, we usually refer to time-restricted eating windows in which you eat your calories (yes, the SAME amount you would eat on a regular day) in a specified time period, and fast for the rest of the time. This is NOT an excuse to eat less.

If you’re dropping calories and fasting at the same time, your body will inadvertently go into STARVATION MODE. Your body knows that there’s no food coming in, so it drops its metabolism as a means to SURVIVE.

Resting Metabolic Rates (RMR)– the energy needed to keep the heart pumping, the lungs breathing, your brain thinking, your kidneys detoxing- have been shown to decrease significantly during calorie-restricted diets. Your body will also start GAINING WEIGHT as a way to keep some energy stores for future bouts of starvation.

So what’s the key difference between Fasting and Restricted Calories?


When we eat, our insulin levels are elevated and our bodies are told to store energy for future use. However, when there are NO calories coming in, our bodies have to make THEIR OWN energy by tapping into body fat stores and converting it into glucose – this process is known as gluconeogenesis.

However, the moment we send the signal to our body that there are calories, EVEN JUST A LITTLE, it will start the storage process. And when it gets used to the idea that there aren’t ENOUGH calories to sustain metabolic activity, it will be more likely to store these calories as body fat to protect you.

The benefits of fasting only arise when you’re completely fasted and spikes in insulin levels don’t occur. So if you’re having a milky coffee in the morning instead of breakfast, a nibble of something here and there, juices or smoothies… this is NOT fasting. You’re now sending signals to digest food and your body thinks that there should be ample calories coming in.

You should not be using “fasting” as a guise to restrict calories; intermittent fasting doesn’t mean just skipping meals but drinking your calories. This is not how it works. If you’re doing this, then you are putting yourself in Low-Calorie Purgatory, stressing your body out even more and will likely end up in starvation mode with a slowed metabolism, difficulty in losing body fat and wastage of essential muscle mass.

Men vs. Women

It is important to note that, in general, men fare better on fasting protocols than women. This is because the hormones regulating key functions like ovulation are incredibly sensitive to women’s energy intake. The chain reaction of female sex hormones happens on a specifically timed cycle, dictated by GnRH (gonadotropin releasing hormone) pulses. These pulses seem to be extremely sensitive to environmental factors and stress – some evidence even shows that a single skipped meal puts us on high alert!

Let us not forget that from an evolutionary standpoint, females were made to bear children. The female body intuitively knows that it shouldn’t get pregnant if there is a risk of illness or death; unfortunately, it doesn’t know the difference between running from a predator and less fatal physiological stress like fasting.

Being too lean is a reproductive disadvantage.

For both genders, being under chronic stress results in the production of cortisol (a stress hormone) taking priority over sex hormone production (a.k.a. the pregnenolone steal). This manifests as low levels of estrogen and/or testosterone with downstream symptoms like: fatigue, depression, low libido, weight gain, and mood swings.

Ultimately, we must remember that fasting is a stressor on the body, regardless of whether we find it mentally stressful or not. If you are under stress from other areas in your life, think about whether adding a fasting protocol in would be more beneficial or detrimental to your health.

In summary:

  • Fasting is NOT a diet. Regardless of how you time your fasts, you should still be averaging your maintenance level of calories everyday.
  • Fasting means NO calories, not less calories. Drinking your calories doesn’t inherently mean you are fasting.
  • The benefits of fasting are suggested to be a result of keeping insulin spikes low; it should be considered more of a therapeutic protocol than a weight-loss diet.
  • Fasting affects men and women differently – women are generally more sensitive hormonally; but it is still a major stress on the body, regardless of gender.

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