10 Intermittent Fasting Benefits: Weight Loss and Beyond

10 Intermittent Fasting Benefits: Weight Loss and Beyond

Brian Stanton

Brian Stanton

3 months ago

Intermittent fasting is wildly popular due to its incredible and wide-ranging potential health benefits.

The most promising (and desired) benefit of fasting is weight loss. When you compress your feeding window or take a day off from eating, fat loss often follows.  

But the benefits don’t end there. Fasting can also positively affect metabolism (lower blood sugar, lower insulin, ketone production), cellular recycling mechanisms (autophagy), the wake-sleep cycle, and even productivity. 

This article is a science-based tour of these benefits. First, let’s set the stage with a definition of fasting. 

What Is Fasting?

A fast is a period of temporary calorie restriction. During this period, you consume zero calories or significantly fewer calories than your metabolism demands. 

The length of your fast and the level of calorie restriction depends on the type of fasting you practice. There are two main types of fasting:

  1. Intermittent fasting
  2. Extended fasting

An intermittent fast starts at 12 hours and ends at around 36 hours. Intermittent fasting can be practiced daily (12/12, 16/8, OMAD) or weekly (5:2, ADF/Alternate-Day Fasting). 

The daily protocols—also called time-restricted feeding—involve eating all your calories in a compressed window. The weekly protocols involve limiting calories (0-25%) on dedicated “fasting days” during the week. Both types of protocols have been shown to have benefits.[*][*

An extended fast is any which lasts longer than 36 hours. It shouldn’t be undertaken lightly and generally requires medical supervision. 

The benefits of intermittent and extended fasting largely overlap. Both entail temporary calorie restriction, but intermittent fasting is the gentler, more sustainable method. 

If you’re new to fasting, start with shorter intermittent fasts. Let’s review the benefits of this practice now. 

The Benefits of Fasting

Humans evolved in a time before minimarts, Grubhub, and “fourth meal”. When food was scarce, our ancestors fasted. 

During these fasts, they would burn fat and make ketones to fuel the brain. Then they would refeed and rebuild their bodies.

These days we’re constantly feeding and never fasting. If we can bring back the fasting part, we could potentially see huge benefits to our health. 

#1: Weight loss

Most people fast to lose weight. It’s the primary selling point for intermittent fasting. 

And it’s not an empty selling point. Multiple studies show that intermittent fasting can help both obese and non-obese people lose weight.[*][*]

What’s driving this train? To answer, we have to talk about negative energy balance. 

When you’re in a negative energy balance, you’re consuming fewer calories than your body is using through resting metabolism, exercise, and daily activities. In other words, you’re eating less than you’re burning. 

The connection to fasting is straightforward. When you fast, less energy is coming in than going out. That’s a formula for weight loss.[*

When calories were held constant with one-meal-a-day intermittent fasting, researchers didn’t find a weight loss benefit vs. three meals a day in normal-weight people.[*] They did, however, see improvements in body composition (more fat loss) in the OMAD condition. That means that even when study subjects ate the exact same amount of food, they lost fat and improved body composition just by splitting those calories into two meals rather than three. 

#2: Ketosis

When you take a break from eating, the hormone insulin stays low. Low insulin, in turn, helps you burn body fat and make ketones. 

This fat-burning state is called ketosis. Benefits of ketosis may include:

  • More stable energy
  • Reduced cravings
  • Better appetite control 
  • Enhanced mental acuity
  • Body recomposition (visceral fat loss)
  • Increased “good” HDL cholesterol
  • Lower blood sugar and insulin levels
  • Lower blood pressure
  • Improvements to metabolic syndrome
  • ...and more

The research on ketosis for cognition is fascinating. In both animals and humans, higher levels of ketones have been linked to better mental performance in a variety of contexts.[*][*

#3: Lower blood sugar

When a person constantly eats—especially if they’re continually consuming carbs—their blood sugar stays chronically elevated. This condition, called hyperglycemia, is the defining clinical feature of type 2 diabetes and is linked to a host of complications, including heart disease.[*][*]  

Overeating has reached epidemic proportions in the Western world, and we have developed an unhealthy dependence on sugar. Are we really surprised we have a collective blood sugar problem?[*]

Fasting may be part of the solution. One randomized controlled trial found that a year of 5:2 fasting lowered average blood sugar in people with type 2 diabetes, while other case reports have shown similar results.[*][*] Promising stuff, but more research is needed. 

#4: Autophagy (Anti-Aging)

Fasting activates a cellular cleanup program called autophagy. When a cell undergoes autophagy, it digests old and damaged parts and replaces them with fresh ones. 

Higher levels of autophagy have an anti-aging effect in animals, which may be true in humans too.[*] When autophagy is impaired, the brain, heart, kidneys, and other organs suffer.[*][*

As a general rule, longer fasts have the potential to activate more autophagy than shorter fasts. But since autophagy is so hard to measure, nobody knows the optimal protocol. 

#5: Brain health

Entering ketosis during a fast isn’t just about burning body fat. It’s also about making ketones that fuel your brain. 

Normally, your brain runs entirely on glucose. But in a state of ketosis, ketones shoulder much of that burden. 

Ketosis appears to have cognitive benefits in both humans and animals. For instance, in older people, elevating ketone levels led to better performance in a variety of mental tasks.[*

Ketosis may also be therapeutic for Alzheimer’s disease. Research on Alzheimer’s suggests that the aging brain loses its ability to use glucose as fuel, leading to cognitive impairment.[*

But the aging brain doesn’t seem to lose its ability to use ketones. Stay tuned for more research on this front. 

#6: Heart health

Any intervention that helps with obesity (a major heart disease risk factor) has the potential to benefit the heart.[*] Fasting included. 

But it’s not just weight loss. Intermittent fasting has also been shown to improve other markers of heart health. 

For example, one review found that alternate-day fasting (ADF) reduced low-density lipoprotein (LDL) cholesterol and triglycerides—both positive movements for heart health.[*] And another found that intermittent fasting improved cardiovascular risk markers similarly to continuous calorie restriction.[*

Still, we don’t have data on fasting for preventing hard outcomes like a heart attack or stroke. 

#7: Anti-inflammatory effects

Another benefit of having ketones in your blood? Anti-inflammatory effects. 

Specifically, the ketone body beta-hydroxybutyrate has been shown to suppress an inflammatory complex called the NLRP3 inflammasome.[*] It sounds like a droid from Star Wars, but it’s actually central to the damaging, unnecessary immune response known as chronic inflammation. 

Fasting may reduce the risk of high blood sugar (hyperglycemia)—a pro-inflammatory state. When you eat less (and less frequently), you have the potential to reduce blood sugar levels. 

#8: Cancer

The signs that fasting may help with cancer are promising. 

First, consider the Warburg Effect—the tendency of cancer cells to suck up glucose.[*] Keeping blood glucose low with fasting may starve cancer of its favorite fuel. 

A similar principle applies to insulin. Insulin is a growth hormone, and high insulin levels have been linked to increased rates of cancer.[*] Fasting can help to keep insulin low. 

Getting to specific data, researchers have found that fasting increases the effect of chemotherapy in mice.[*] And in women with HER-2 negative breast cancer, a 24-fast was shown to reduce toxic side effects of chemotherapy.[*]

#9: Circadian rhythm enhancement

The circadian rhythm is your 24-hour wake-sleep cycle. Its proper functioning affects every area of human health, including sleep quality, fat metabolism, and energy levels throughout the day. 

By not snacking overnight—the most basic form of time-restricted feeding— it is possible to enhance your circadian rhythm.[*] You give your body a chance to wind down and promote restful sleep. You tune up your fat-burning capacity. You skip the needless calories—all good things.

#10: More productive time

Time-restricted feeding also frees up your schedule. When you don’t have to worry about meal prep, eating, and cleanup, your calendar opens up nicely. 

Skipping breakfast can be a valuable productivity hack. You conquer the hard stuff on an empty stomach, and then you treat yourself with a rewarding lunch. 

In a sense, your brain is like a trained seal. If you toss it a fish when it does something good, it will soon associate the behavior with the reward. 

Knowing the reward is coming will motivate the behavior. You’ll not only get more work done, but you’ll enjoy it more. 

Hydration While Fasting

Since fasting has a diuretic effect, it’s essential to replace fluids regularly. This helps prevent dehydration symptoms like fatigue, headaches, and weakness. 

What can you drink? As long as the beverage contains minimal calories, it shouldn’t meaningfully interfere with your fast. 

Healthy options include:

  • Water
  • Tea (herbal, green, or black)
  • Coffee
  • Lemon water
  • Beverages sweetened with stevia, monk fruit, or erythritol 
  • Bone broth

Keto Beef Bone Broth is an excellent option because it provides electrolytes like sodium, calcium, and phosphorus. Along with water, fasting makes you excrete electrolytes at higher rates[*]—so it’s crucial to replace them. 

An important point to note, drinking plain water and neglecting electrolytes will only exacerbate an electrolyte deficiency, provoking a series of unpleasant symptoms.[*]  

What To Eat During Your Feeding Window

When you practice any form of fasting, proper nutrition is essential. You have a limited window in which to cram protein, fatty acids, vitamins, minerals, and polyphenols. You need to make that window count. 

Whenever possible, select foods based on nutrient density. For example, vegetables are more nutrient-dense than grains, meat and fish are more nutrient-dense than protein powder, and real eggs are more nutrient-dense than chocolate eggs. (Um, thanks Captain Obvious!). 

Your calories during feeding windows will come from protein, fat, and carbs—the three main macronutrients. Of the three, focus on getting enough protein first to help maintain muscle, synthesize hormones, and support a vast array of biochemical reactions. 

Because protein kickstarts the growth and repair process, it’s wise to break your fast with a high-protein meal. Meat, fish, and eggs are all excellent sources, or opt for tofu or tempeh for a plant-based protein boost.

For fasts 24 hours or longer, make your first meal back a high-protein snack of 200-300 calories. (Eat a bigger meal about an hour later). This helps put the brakes on muscle loss and stimulates satiety hormones, so you don’t subsequently overeat. 

One final point is to consider eating a Keto diet to support your fasting regimen. Eating Keto helps you fat-adapt. This makes it easier to access body fat during a fast and simultaneously helps to reduce hunger hormones.[*

The point is that Keto and fasting work together like a Swiss bobsled team: efficiently.      

What to Expect With Fasting

If you’re new to fasting, it’s important to set realistic expectations. The benefits won’t occur overnight, at least not in full force. 

The key is to find a sustainable fasting protocol that you can stick with and that is suitable for your individual health needs. Start with 12 or 13 hours of time-restricted feeding and work your way up as comfort and schedule permit. 

Better still, ease yourself through the process using a diet tracking app like Carb Manager to help build your custom intermittent fasting program. This is a great way to manage all your essential health and dietary metrics while tracking your long term fasting goals and progress.

Just remember, shorter fasts can be just as beneficial as longer fasts. It all depends on your goals and unique physiology. Find what works for you, and enjoy the journey. 

Please note that as with any significant diet or lifestyle change, we recommend working alongside a registered health professional, especially if you are currently on any prescribed medications or undergoing any medical treatments. Fasting is not appropriate for everyone and should be avoided by those with a history of eating disorders, pregnant and breastfeeding women, and anyone under 18. 

Comments 19

  • PerkyPepper0316

    PerkyPepper0316 22 days ago

    I’m curious as to whether there is a nutrition professional that helps advise answers to these questions as most appear to be unanswered.

    • DougieWugs

      DougieWugs 23 days ago

      My feeding window is 11 am to 7 pm. I ate at 230 pm and it said I didn't complete my fast? Why?

      • Malaun

        Malaun a month ago

        I often log my food during the fasting hours. The app thinks i am eating then! Can I resolve this?

        • Debby

          Debby a month ago

          Can I have MCT oil in my coffee for breakfast while fasting

          • Racer704

            Racer704 6 days ago

            MCT oil does break a fast,but some believe that since it goes straight to your liver it doesn’t break a fast. Thomas Delaur might be spelled wrong has a YouTube channel and says it does break it

          • LADY BUBBLE

            LADY BUBBLE 20 days ago

            I need 2 know about coffee additives, too. I don't find answers here. Ty 4 addressing this.

        • Outstanding Choices

          Outstanding Choices a month ago

          Hi . Today is my first day on my fast what happens if I don’t drink and eat all my calories in my window time ?

          • StellarAvocado184086

            StellarAvocado184086 a month ago

            I see all these questions, but only one answer? Did y’all ever get an answer?

            • LADY BUBBLE

              LADY BUBBLE 20 days ago

              I am looking 2 answers as well! All good questions. R they sent 2 our inbox?

          • JschmidtO525

            JschmidtO525 2 months ago

            I wish it had ADF as an option in the fasting choices. I only lose weight if I do >24-36 hr fasts recommend by my dr.

            • Robinahood72

              Robinahood72 14 days ago

              If you can figure multi day fast I would appreciate that info as well

            • Maryanne1966

              Maryanne1966 a month ago

              for weight loss benefit? i have just started a 72 hour (i started yesterday)

            • Onesys01

              Onesys01 a month ago

              If you can figure out how to do a multi-day fast I would really appreciate it too. I find that fasting between 72 and 96 hours is the best. For me

          • Sue

            Sue 2 months ago

            It would definitely be helpful like other fasting apps that give you the option on a clock like timer to adjust it without having to create several fasting schedules using "custom/create fasting " I have to two alternating schedules depending on my work and life schedule. I practice 11am to 7pm, 10am to 6pm and 12noon to 8pm. I created those schedules and choose accordingly 😁 this is a new add on so hopefully they tweak it to be more friendly user😁

            • Ugotitgirl

              Ugotitgirl 2 months ago

              I have the same question how do you change the fasting starting time?

              • Mesa Mike

                Mesa Mike 2 months ago

                Just create a Custom Fast

            • Bridgebyketo

              Bridgebyketo 2 months ago

              How do I change time started fasting??

              • jlongnett

                jlongnett 20 days ago

                See above post. Create a custom fast.

            • Chelee13

              Chelee13 2 months ago

              I can't seem to get back into ketosis since I started my 16/8. Any suggestions?