Intermittent Fasting Before And After: What Is It & How It Works? (2023)

Intermittent fasting is a popular diet trend circulating through the health industry. It is a specific diet plan focused on fasting, or not eating, for an extended period throughout the day.

The basic theory behind this diet is that when fasting, the body will burn fat instead of food for fuel, resulting in significant weight loss rather quickly. The results of intermittent fasting before and after can knock your socks off! You can follow various plans to try out intermittent fasting for yourself.

Intermittent fasting may also contribute to other health benefits, such as regulating hormones and living longer.

With all of these benefits, intermittent fasting might sound too good to be true, and you might want to know how long does it take to work? In this article, we will answer all of your burning questions about how intermittent fasting works and dive deeper into the benefits and safety of this diet.

What Is Intermittent Fasting?

Intermittent fasting is a specific diet plan focused around windows of eating and fasting. In this diet, you eat all of your meals in the day during one particular restricted time frame[1]. This diet plan requires users to go many hours between meals, much longer than they would typically go on a regular standard diet.

How Does Intermittent Fasting Work?

Intermittent fasting works by tapping into how the body utilizes glucose to produce energy. The body runs on glucose. When we are not taking in glucose through our meals, the body will find other ways to get this crucial fuel.

Typically, with a standard diet, the body will break the food down after you consume a meal. This meal will be a significant source of glucose for the body. The glucose it obtains from each meal will be used to make energy to run the body’s processes.

When on an intermittent fasting diet plan[2], you will only eat during the eating window. During the fasting period, the body will be forced to obtain glucose to produce energy from other sources. One of the ways it does so is by breaking down fat stores. As the fast continues, the body will break down fat stores for energy. The breaking down of fat can lead to increased weight loss.

Intermittent Fasting Plans

Intermittent Fasting Before And After: What Is It & How It Works? (2)

Many variations of intermittent fasting plans are available and can be tailored to best suit your lifestyle needs. Keep in mind, there isn’t a one-size-fits-all plan for intermittent fasting, so it is best to weigh the options on which method works best for you.

One of the more popular intermittent fasting plans is the 16:8 plan. In the 16:8 plan, you will fast for 16 hours and eat during an 8-hour window. Typically, the 16-hour fast is partially taken up by the time you’re sleeping, making it easier to fast for a longer duration. A standard 16:8 plan might look like eating your first meal at noon, the last meal by 8 PM, and fasting overnight. Black coffee is allowed in the morning without breaking the fast.

Another intermittent fasting plan is the 5:2 diet. The 5:2 diet involves alternating eating patterns throughout the week rather than restricting calorie intake daily. In the 5:2 plan, dieters will eat a normal amount five days a week. They will have a very restricted calorie intake twice per week, typically around 500 calories. The way the 5:2 diet is designed makes your total calories for the week significantly less than if you were to eat normally all week. This plan usually results in a calorie deficit and subsequent weight loss per week.

It is best to discuss intermittent fasting with a nutritionist or your doctor before starting. There are even intermittent fasting apps you should try that will help most people stick to their plan!

Intermittent Fasting Before And After

Intermittent Fasting Before And After: What Is It & How It Works? (3)

Intermittent fasting can result in considerable weight changes for the right person. It can take some time on the diet to begin losing weight but once you do, there might be some significant changes!

A great way to get a show-stopping before and after result is to tailor the diet to your needs. One way to do this is to look into specific diet recommendations for your race, age, or gender group. For example, intermittent fasting for women over 40 might be particularly challenging, so tapping into other women’s “do’s and don’ts” might help you create an even better plan. Always speak with your doctor or nutritionist for the most tailored diet recommendations.

Intermittent Fasting Benefits

Intermittent fasting has many benefits, such as weight loss, hormonal regulation in chronic conditions, and longevity. Below we will explore each of these benefits in further detail.

Weight Loss

Probably the most popular reason to begin intermittent fasting is for weight loss. People usually use intermittent fasting to lose weight because of the narrow window of opportunity to eat and the concept that it can help with fat loss. Studies have shown these metabolic shifts[3] can contribute to weight loss.

Intermittent fasting also might make it easier for someone to eat a smaller amount every day than they typically would on a standard diet because of the short window allowed for eating. Many people are guilty of “grazing” or snacking throughout the day. Snacking can quickly add up to many extra calories leading to weight gain. Studies have shown that sticking to a small window of eating reduces the risk of consuming excess calories[4] and may result in additional fat loss.

Studies have shown that weight loss[5] is a potential benefit of intermittent fasting. However, the jury is still out on whether it is more effective than a typical calorie-restriction diet. This is why it is always best to listen to your body and follow a diet plan that feels right for you.

Hormone Regulation

Also, intermittent fasting has been shown to help with hormone regulation, especially with glycemic control. Out of control hormones can lead to weight gain. This diet might be beneficial in those with blood sugar issues such as type 2 diabetics.

During a fasted period the body must regulate its blood sugar level, and does not receive a spike in blood sugar from food. This helps to maintain a lower daily blood sugar level, which has been shown to decrease risk of diabetes and result in better glycemic control in diabetics[6].

Another way intermittent fasting helps with hormone regulation is it alters the way the body responds to a meal after fasting. Studies have shown that after a fasted period[7] the body will actually increase the rate of glucose uptake and also increase insulin sensitivity[8]. Increased insulin sensitivity and glucose uptake may result in lower blood sugar, and this can help diabetics maintain better blood sugar control.


Numerous studies have linked intermittent fasting to living longer. This is a huge potential benefit of switching to the eating plan permanently.

This concept was first proven in a study on rhesus monkeys[9]. They were given an intermittent fasted calorie reduced diet and compared to monkeys on their normal diet. The monkeys in the fasted group lived significantly longer than the members of the normal diet group.

The scientific community has explored this concept, and even identified some of the specific molecules[10] and genes[11] that may be responsible for the observed increased lifespan.

Is Intermittent Fasting Safe?

Intermittent fasting is generally safe for healthy people[12], but it could pose a potential risk for specific populations. Always consult your doctor before starting a new diet.

Specific populations should avoid intermittent fasting. This includes people under 18, pregnant or breastfeeding women, people with type 1 diabetes, or those with a history of an eating disorder.

It can be a permanent lifestyle change for those who do well on an intermittent fasting diet. However, if you experience any new symptoms after switching to an intermittent fasting diet, such as headaches, nausea, or lightheadedness, speak with your doctor immediately.


Intermittent fasting is a popular diet trend that requires dieters to restrict their food intake to specific windows of time. There are various plans, including the 16:8, 5:2, or alternate-day plan. It is best to pick a plan that will fit with your lifestyle.

Intermittent fasting touts many benefits. It can lead to significant weight loss, better glycemic control, and it might even lead to a longer lifespan with good health.

Although intermittent fasting can be a great diet plan for specific populations, it might not agree with everyone. Whether or not intermittent fasting will work for you can vary based on your metabolic profile, food choices, medical history, and personal tolerance for fasting. Before starting any new diet, you should discuss these plans with your doctor to ensure they are right for you.

+ 12 sources

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  1. To (2019). To Fast or Not to Fast. [online] NIH News in Health. Available at:
  2. Santos, H.O., Genario, R., Tinsley, G.M. and João Felipe Mota (2022). A scoping review of intermittent fasting, chronobiology, and metabolism. [online] ResearchGate. Available at:
  3. Mandal, S., Simmons, N., Awan, S., Karim Chamari and Ahmed, I. (2022). Intermittent fasting: eating by the clock for health and exercise performance. [online] 8(1), pp.e001206–e001206. doi:
  4. Gabel, K. and Varady, K.A. (2022). Current research: effect of time restricted eating on weight and cardiometabolic health. [online] 600(6), pp.1313–1326. doi:
  5. María Morales Suárez-Varela, Ester Novoa Sánchez, Peraita-Costa, I., Llopis-Morales, A. and José Miguel Soriano (2021). Intermittent Fasting and the Possible Benefits in Obesity, Diabetes, and Multiple Sclerosis: A Systematic Review of Randomized Clinical Trials. [online] 13(9), pp.3179–3179. doi:
  6. Ganesan, K., Yacob Habboush and Dagogo-Jack, S. (2020). Calorie Restriction and Intermittent Fasting: Impact on Glycemic Control in People With Diabetes. [online] 33(2), pp.143–148. doi:
  7. Journal of Applied Physiology. (2020). Effect of intermittent fasting and refeeding on insulin action in healthy men | Journal of Applied Physiology. [online] Available at:
  8. Ganesan, K., Yacob Habboush and Dagogo-Jack, S. (2020). Calorie Restriction and Intermittent Fasting: Impact on Glycemic Control in People With Diabetes. [online] 33(2), pp.143–148. doi:
  9. Mattison, J. (2003). Calorie restriction in rhesus monkeys. [online] 38(1-2), pp.35–46. doi:
  10. Green, C.L., Lamming, D.W. and Fontana, L. (2021). Molecular mechanisms of dietary restriction promoting health and longevity. [online] 23(1), pp.56–73. doi:
  11. Gisele Pereira Dias, Murphy, T., Stangl, D., Selda Ahmet, Morisse, B., Nix, A., Aimone, L., Aimone, J.B., Makoto Kuro-o, Gage, F.H. and Sandrine Thuret (2021). Intermittent fasting enhances long-term memory consolidation, adult hippocampal neurogenesis, and expression of longevity gene Klotho. [online] 26(11), pp.6365–6379. doi:
  12. Anic, K., Schmidt, M.W., Furtado, L., Weidenbach, L., Marco Johannes Battista, Schmidt, M., Schwab, R., Brenner, W., Ruckes, C., Lotz, J., Lackner, K.J., A Hasenburg and Hasenburg, A. (2022). Intermittent Fasting—Short- and Long-Term Quality of Life, Fatigue, and Safety in Healthy Volunteers: A Prospective, Clinical Trial. [online] 14(19), pp.4216–4216. doi:


How many days do you have to intermittent fast to see results? ›

After beginning your intermittent fasting routine, you could see changes in your body in as little as ten days. More significant weight loss is seen after two to ten weeks. Keep in mind that your overall health (and how your body feels) is more important than the speed of your weight loss.

What happens to your body the first week of intermittent fasting? ›

In the first week, you may also find it difficult to get proper sleep at night. At night you may feel famished or thirsty. You may even wake up frequently just to drink water and may find it difficult to fall asleep again. It happens due to calorie restriction and changes in lifestyle patterns.

What is the most successful method of intermittent fasting? ›

Alternate day fasting is probably one of the most effective forms of intermittent fasting because the fasting period is so long. Studies have shown time and time again how effective this method can be with helping individuals lose weight, control their blood sugar levels, decrease their blood pressure, and more (4, 5).

How much weight can you lose in a month with intermittent fasting? ›

If you consistently stay active while following intermittent fasting, you can lose as much as 6-8 pounds per month.

What is the best intermittent fasting window to lose belly fat? ›

The 16/8 method

The 16/8 intermittent fasting plan is one of the most popular styles of fasting for weight loss. The plan restricts food consumption and calorie-containing beverages to a set window of 8 hours per day. It requires abstaining from food for the remaining 16 hours of the day.

How do I get the fastest results from intermittent fasting? ›

Tips for maintaining intermittent fasting
  1. Staying hydrated. ...
  2. Avoiding thinking about food. ...
  3. Resting and relaxing. ...
  4. Making every calorie count. ...
  5. Eating high-volume foods. ...
  6. Increasing the taste without the calories. ...
  7. Choosing nutrient-dense foods after the fasting period.

Why is 16 hours the magic number for fasting? ›

The benefits of a 16-hour fasting schedule are the same as a 12-hour fasting. They include weight loss, aid in the cellular repair process, improved sleep, improved digestion, increased mental health and clarity, and reduced insulin resistance.

Which part of body loses fat first during intermittent fasting? ›

You will first lose hard fat that surrounds your organs like liver, kidneys and then you will start to lose soft fat like waistline and thigh fat. The fat loss from around the organs makes you leaner and stronger.

What is the first rule of intermittent fasting? ›

Eating during a 12-hour window every day (between 7 a.m. and 7 p.m., for example) and fasting for the other 12 hours. Eating during an 8-hour window every day (between 11 a.m. and 7 p.m., for example) and fasting for the other 16 hours.

How many days a week should I intermittent fast to lose weight? ›

5-2 fasting

Eat a normal diet five days a week and fast two days per week.

How long does it take for 12 12 intermittent fasting to work? ›

According to experts, 12 hour intermittent fasting results can be visible after at least ten weeks of following the routine. The average weight loss within this period is between 7 and 10 pounds.

Why am I not losing weight on 16 8 fasting? ›

When you fast for shorter durations, your body doesn't have enough time to go into ketosis. This means it won't burn stored fat, and there won't be significant weight loss. As one study concluded, a fasting window of 18-19 hours is more effective in terms of weight loss than those between 12-17 hours [11].

How many days a week can you do 16 8 intermittent fasting? ›

How often should you do 16:8 intermittent fasting? You can do anywhere from one day of intermittent 16:8 fasting to seven days a week, because, unlike other intermittent fasting diets, each day of the 16:8 works independently to the rest.


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