How Long Does it Take to See Results from Intermittent Fasting?

Intermittent fasting shouldn’t be considered a “quick fix” for losing weight, but rather a sustainable long term lifestyle change. In as little as two weeks, you can start noticing changes.

If you’re like most people, the reason you started intermittent fasting in the first place was to achieve some amount of weight loss. However, being the impatient species we are, we want things immediately. But with anything in life that is worth having, it takes time to achieve your goals.

With that in mind, you may be wondering exactly how long does it take to see results from intermittent fasting, and the answer to that is that “it depends”. We know, there’s nothing more frustrating than hearing the dreaded “it depends” response when you want a definitive answer. But this is actually a good thing that could mean you see results sooner than the next guy who did not have everything dialed in to pull off effective weight loss.

Which begs the next question, what do results depend upon? These are the criteria that you should spend your time refining in order to shorten the amount of time it takes to observe meaningful changes.

Are you ready to learn? Intermittent fasting school is in session!

My Personal Experience With IF

I’ve experimented with many versions of IF, some of which aren’t even officially “a thing”. From my trials, the 16:8 would have to be my personal recommendation. I easily knock off at least 50% of this during sleep, and if I have dinner early enough (say 19:00 HRS) I can eat again by 11:00 HRS the next day.

Not too shabby.

IF shouldn’t be considered a “quick fix” for losing weight, but rather a sustainable long term lifestyle change. In as little as two weeks, you can start noticing changes. I have also noticed a difference from as little as week one, but from my experience, this could just as easily be water weight and not true “fat”.

I’ve also found that performing cardio while fasting helps offer better results than weights, since my goal at that time is to promote fat utilization. Weight training during my re-feeding intervals also means that I can adequately supply my muscles with nutrients to kick start recovery and take advantage of the anabolic window.

A small amount of branched-chain amino acids (BCAAs) can also help spare muscle while exercising in a fasted state, especially if you are prone to losing muscle mass easily. Just not too much, or you will trigger an insulin spike and shutdown the beneficial process of lipolysis.

If I were to sum up what to expect in a timeline it would be this:

Day 1-3: regretting life decisions and wanting to curl up in my mama’s lap, ha! Ok, not that dramatic. But what you will probably feel is reduced bloating. I never truly appreciated how bloated I was until it started to actually subside.

Day 4-7: slight reduction in appetite, dealing better with the fast. Pants may feel a little looser.

Day 8-14: energy levels bounce back. Feeling comfortable with the fast. Actually seeing something a bit different in the mirror.

Day 15-30: retraining your body. Skin improves, bowel and digestive health on fleek. Energy levels feel great. Weight is definitely down as indicative from scales or measuring tape. Learning to assess new exercise tolerance while fasted.

Day 31 and beyond: you’re on your way. You have done better than the majority of people, and should find it exponentially easier to stick to it. Great job.

The Intermittent Fasting Model That You Follow

The speed at which you see results after starting intermittent fasting can tie in to which one of the three popular spins on the diet you choose to run with. For instance, the classic 16/8 diet, while very effective is not the best suited for extremely rapid weight loss. Rather, its primary goal is consistent weight loss over the long term, a strength that other varieties do not necessarily possess.

In contrast, consider the 5:2 diet or Eat Stop Eat. These IF varieties heavily emphasize significant caloric restriction two days per week (or one in the case of Eat Stop Eat, if desired) that will in turn manifest as significant weight loss over a short period of time.

In terms of sheer speed, eat stop eat would reign supreme as you go one or two days per week with absolutely no calories, in turn causing the body to dig deep into stored body fat in an effort to support energy production. 5:2 diets are not as restrictive, as you still consume a minimal amount of calories daily, but it is still very effective for its speed.

The Determining Factors: What Governs IF effectiveness?

Your Current Physical State

It is common knowledge that it becomes significantly more difficult to lose body weight the leaner you are, which would explain why it is possible to go many weeks on an intermittent fasting diet protocol and not see changes on the scale.

If you start out with a high volume of body fat, you may begin to see rapid changes in as little as a week. This consideration is often overlooked but needs to be kept in mind- do not compare the progress of others with your own as genetic, or even environmental factors can account for big differences in weight loss.

Your Goals

Most frequently the goal of intermittent fasting is to bring about weight loss, however this is not the only indication of this diet, as it can also be an effective way of helping you gain lean muscle mass while limiting how much fat you gain in the process.

Gaining muscle on intermittent fasting diets is more difficult than it is while consuming food around the clock, simply because nutrient timings become even more important. In addition to this, not all intermittent diet types lend themselves well to muscle hyper trophy. If you have your eye on muscle gain, it is a good idea to opt for the 16/8 diet. Other IF varieties could mean that results trickle in at a snail’s pace considering that caloric intake is significantly low (or non-existent) a couple times weekly.


Yes, it’s true that age is just a number, but it is an important number that indicates fairly accurately important factors such as metabolic rates. Why is this important? Your metabolic rate determines how many calories you burn daily while at rest (also known as the resting metabolic rate RMR/BMR).

As you age muscle sarcopenia also negatively impairs metabolic rate, as the muscle loss that occurs means that there are less active mitochondrial units in muscle cells to make use of consumed calories. Muscle sarcopenia is the name of the condition that arises naturally as we age characterized by muscle loss. As a result, the body is unable to make use of the same consumed calories with weight gain occurring much more easily.

Results from intermittent fasting will likely come about slower as well, since caloric utilization is reduced. However, age-related metabolic slowdown and the muscle loss (sarcopenia) that occurs can be mitigated to an extent by regularly partaking in strength training exercises that help to preserve muscle mass. (Hint: combine weightlifting with intermittent fasting for synergistic effect).

Your Nutrition Plan

Apart from the metabolic advantages intermittent fasting offers the body, the other significant benefit associated with it is a reduction in calories that usually accompanies restricting food consumption patterns to specific periods of time.

Logic should indicate that you would not be able to consume the same amount of calories in an eight hour period compared to if you are free to consume food throughout the day. Likewise, restricting calories one or more days per week yields the same effect of reduced caloric intake – at least it should.

However, occasionally things go very wrong. For instance, it is possible for you to go overboard during those eight hours by eating significantly more than you would over the course of a normal day. The same applies to the significant calorie deficit caused by the other IF diet approaches, a scenario referred to as compensatory eating.

A large part of this “reflex” action is believed to be psychological in nature, though it cannot be ruled out if hormones play a key role as well. Compensatory eating also affects individuals on the other end of the spectrum especially those diagnosed with bulimia nervosa, who overeat and subsequently purge to ameliorate their self-induced actions.

Staying Hydrated

Though water isn’t often considered a nutrient, it is, and arguably one of the most important. Dehydration to a mild degree (as little as 2-3%) can impair your performance significantly, and also metabolic processes inclusive of fat burning.

Water is the vehicle in which all chemical processes in the body take place, so even a minor reduction in water volume can have far reaching implications. To ensure that your efforts with intermittent fasting are rewarded, be sure to stay hydrated- drink in excess of two liters daily, oftentimes double this amount in hot weather and if the need arises.

Getting The Most Out Of Intermittent Fasting Tips

Without a doubt, fasting for a prolonged period of time will inevitably bring about weight loss, but that doesn’t mean that there aren’t ways which exist that can make things even better.

Consider these insider tips that can leave others questioning what your secrets are!

  1. Fasting does not equate to total starvation – a common misconception is that while fasting you must absolutely stay away from anything even modestly resembling nutrition. This isn’t entirely correct since hunger can derail even the most well-intentioned diet plan.
  2. Use MCT OilMCT oil, otherwise known as medium-chain triglyceride oil, is considered a high-performance type of fat, one which is treated differently from typical fats. You might probably be thinking that the use of MCT oil would definitely knock you out of the fasting window, but this is actually not true. MCT oils are not taken up by cells and subsequently stored, but rather used to facilitate the synthesis of ketone bodies; alternative energy sources your body uses when carbohydrates are scarce. This makes MCT oil particularly useful in supporting a fat-based metabolism and is a staple of a keto- intermittent style diet.
  3. Drink Coffee and Tea – as long as you don’t have a sensitivity to stimulant based beverages, coffee and tea should be your number two and three beverages respectively (after water, of course), helping to break the monotony of plain H2O. Not only will this help to make the fast seem less brutal, but the caffeine and EGCG (found in tea), will ramp up your metabolism and utilization of fat for energy. If you train while fasting, these beverages may play an even bigger part in your success.
  4. Find Which IF Version is best for you – in general, you’ll want your fast to run less than 24 hours (as undesirable metabolic changes start happening after this), but you’ll also need to find your tolerance level. Personally, I find 16:8 to be my sweet spot, as going much longer makes me feel pretty crappy, not to mention dehydrated.
  5. Start Your Fast After Dinner – starting your fast after dinner is probably the most painless way to fast, typically not eating anything that would kick out the fast until lunch the next day. The key with this strategy is to make it so that the maximum amount of fasting occurs while you’re asleep, thus making it less about hunger and watching the clock.
  6. Do some exercise – not necessarily gruelling high intensity actively that makes you feel like puking, but moderate-intensity work to promote the usage of glucose and glycogen, and subsequently fat. The increased oxygen and caloric requirements post-workout will also encourage the use of more fat, contributing to your goal.


As you can see, there is no single defining variable that influences how soon you will start to see results from intermittent fasting. It is possible to start seeing weight loss in as little as 2 weeks, but this should not be your goal, especially if you do not have a large amount of weight to be rid of.

A consistent, slow approach works best most often as it translates to an increased likelihood of keeping the weight off too.

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Mike Julom, ACE CPT

Mike is an ACE Certified PT and a CrossFit Level 1 Trainer. He is an avid lover of all sports. Basketball, tennis, athletics, volleyball, soccer, squash, golf, table tennis, even darts, you name it! He's a very active CrossFit athlete and has been WOD'ing for over 7 years. With such an intense fitness regime, Mike has learned to take care of his body physically, nutritionally, and spiritually. Mike founded ThisIsWhyImFit as a way to share his vast knowledge of exercises, diets, and general fitness advice.

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  1. Hi Mike
    Interesting article.
    I have been using the 16/8 IF formula. It has been 4-5 weeks since I started and it is very frustrating to see no change in weight. I also work out almost delay with my Peloton and or walking. I do not need to lose that much bu come on!

    • Hi Susan,

      Thanks for reading. Your issue could be caused by numerous factors. Are you maybe eating too much during your eating window because you get too hungry? If so, try distributing that consumption over smaller meals over the course of your window. This allows you to eat lesser but more often.

      At the end of the day, IF is there to help with providing you a caloric deficit – if you’re still consuming more calories that you’re burning, then you’re simply just slowing the weight gain process.

      Let us know how you go!

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