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Can you lose weight by just intermittent fasting?

Most diets require calorie counting to lose weight. Intermittent fasting leads to metabolic changes that cause weight loss without intentional calorie restriction.
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Most diets require a restriction in calories for weight loss. Intermittent fasting, however,  leads to metabolic changes that help to access fat storage. For this reason, intermittent fasting regulates the appetite, and most people lose weight without intentionally restricting calories.

Written by
Christine Richardson, PhD
Clinical Project Manager at Becton Dickinson

There are many popular diet plans and dietary eating patterns that are believed to facilitate weight loss. One of those methods is intermittent fasting

While there are many forms of intermittent fasting, the underlying theme behind all of them is to incorporate short-term fasts for a defined period of time.

Many people who use intermittent fasting as a weight loss strategy tout it for being both easy and effective. 

This article focuses on how intermittent fasting can be a useful tool to achieve your weight loss goals.

What is intermittent fasting?

Intermittent fasting is a popular dietary approach used for weight loss goals and for achieving various health benefits.

Intermittent fasting is an eating strategy where individuals are incorporating fasts of different lengths into their normal routine. Some people simply extend their overnight fast for additional hours while others might fast for full days every week.

Can intermittent fasting help you lose weight?

Yes! Intermittent fasting is an extremely effective strategy to help you shed some unwanted body fat. And the best part is, you don’t have to intentionally restrict your calories in order to do so!

Clock symbolizes intermittent fasting.

Traditionally, most diets require people to count and restrict their calories in order to see any difference. With intermittent fasting, you don’t have to. 

Your goals need to be realistic though, we don't recommend to expect losing 10 pounds in a month for instance, which is unhealthy like we're explaining in a dedicated article.

Burning more fat

With intermittent fasting, you do not need to intentionally decrease the amount of calories you eat each day in order to see results. The reason is because when you decrease your eating window, or the timeframe that you allow yourself to eat each day, you are changing certain metabolic pathways in your body. These changes make your body more adept at using your stored fat for energy for everyday tasks. 

To elaborate, your body can break down either sugar (glucose) or fat and use it to fuel itself. When you don’t eat for an extended period of time, your body tries to conserve its glucose stores and will shift to burning more fat. In other words, when you’re participating in an intermittent fasting dietary pattern, you are “training” your body to burn more of your stored fat, which is how people see such success on an intermittent fasting diet.

An excellent review article was written on this topic and the authors called the ability to train your body to use more fat for fuel “flipping the metabolic switch.” They also argued that this is the underlying reason why people see improvements in their overall health while participating in an intermittent fasting diet (1).

Metabolic changes

Without getting into all of the sciencey details, adhering to an intermittent fasting diet can cause bodily changes that also help cause fat loss. This includes changes to certain hormones and other compounds, like insulin, that can help your body use more fat for energy (2). 

Fasting also causes an increase in 5- AMP-activated protein kinase or AMPK. This compound increases when body sugar levels are in short supply. While scientists still have a lot to learn about AMPK, it appears that this compound also helps your body use more fat for fuel and also plays a major role in allowing for the other health benefits associated with intermittent fasting (3, 4, 5, 6, 7).

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Should you restrict calories while intermittent fasting?

Calculator for calorie counting.

You could also restrict your calories while on an intermittent fasting diet but this may not be as good for you as you think. It has been shown time and time again in the scientific literature that while restricting calories can result in weight loss, much of that weight loss comes from a loss of muscle (8, 9, 10, 11). 

This loss of muscle mass can be detrimental to your fat loss goals because your muscles use a lot of energy/calories. The less muscle you have, the fewer calories you burn each day. This means that in order to maintain your weight loss achievements or to avoid any plateaus, you’re going to have to decrease your calorie intake to adjust for this loss of muscle mass. 

Additionally, when you restrict your calories for an extended period of time, your body goes into a “starvation mode” where it changes different bodily processes to try to conserve energy (12, 13). This means that your body is actually trying to burn less calories every day.

Studies have shown in human and animal studies that maintaining your caloric intake while participating in an intermittent fasting diet doesn’t cause a loss in muscle mass and therefore, there is no change in the amount of calories burned each day (1, 14, 15, 16, 17). These studies also show that you don’t need to restrict your calories in order to see some of the other health benefits associated with intermittent fasting. 

But at the same time, you should not force yourself to eat more when you’re not hungry. By allowing access to your fat storage, intermittent fasting also decreases your appetite. Not being hungry means that your body is happily using your stored body fat, which spares valuable muscle mass.

Intermittent fasting is a good long-term strategy

As mentioned, with intermittent fasting, you don’t have to count calories. This means that you may be happier and less stressed on this diet and may find this diet easier to adhere to long-term. The reason why many diets fail is because people are so miserable while they’re on them that they can only stick to them for a short while. This may not be the case for everyone, but many people say that intermittent fasting is simply easier, and this allows them to have greater success on this diet. 

How to Be Successful

There are a few strategies to try to practice in order to achieve the greatest results:

  • Eating nutritious foods. While you may opt to not count or restrict calories while on intermittent fasting, this doesn’t mean you should consume low-quality foods. Try to make sure that most of your food is nutrient-dense. This means eating lots of fruits, vegetables, “good” fats, whole grains, and lean proteins. Do let yourself have some of your favorite foods! Eating should be a joyful experience, not something you stress out about.

  • Be consistent. You might want to play around with the different forms of intermittent fasting but when you find one that works for you, stick with it. And make sure you clearly define your eating window and don’t let that change much. The key to being successful with intermittent fasting is finding a pattern that works for you and your schedule and making this a priority.

  • Be patient with yourself. You may be hungry during the first week or so of your new intermittent fasting diet. It’s normal and ok-your body is used to eating during most hours you’re awake and it’s going to need some time to adjust. And be patient with yourself if you “mess up” here and there. The key to adopting a new lifestyle habit is that it’s not a temporary thing. This means that some days your schedule might be wonky or you might be stressed out. It’s ok to give yourself grace if you’re not 100%.

In Summary

Intermittent fasting is an excellent weight loss strategy.

You don’t need to count calories in order to lose body fat while on an intermittent fasting dietary pattern. Your body needs food for energy so make sure you are giving your body what it needs!

If you need help with intermittent fasting, join our intermittent fasting community for women only. There, you get all the support you need!

Also, you might be interested in reading our other article about weight loss and birth control.


1. Anton SD, Moehl K, Donahoo WT, Marosi K, Lee SA, Mainous AG, Leeuwenburgh C, Mattson MP. Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting. Obesity. Blackwell Publishing Inc.; 2018. p. 254–68. 

2. Antoni R, Johnston KL, Collins AL, Robertson MD. Effects of intermittent fasting on glucose and lipid metabolism. Proceedings of the Nutrition Society [Internet]. Cambridge University Press; 2017 [cited 2021 May 10]. p. 361–8. Available from:

3. Carling D. AMPK signalling in health and disease. Current Opinion in Cell Biology. Elsevier Ltd; 2017. p. 31–7. 

4. Wu L, Zhang L, Li B, Jiang H, Duan Y, Xie Z, Shuai L, Li J, Li J. AMP-Activated Protein Kinase (AMPK) regulates energy metabolism through modulating thermogenesis in adipose tissue. Front Physiol. Frontiers Media S.A.; 2018;9. 

5. Jeon SM. Regulation and function of AMPK in physiology and diseases [Internet]. Experimental & molecular medicine. Korean Society for Biochemistry and Molecular Biology; 2016 [cited 2020 Jul 2]. p. e245. Available from: /pmc/articles/PMC4973318/?report=abstract

6. Gao F, Chen J, Zhu H. A potential strategy for treating atherosclerosis: Improving endothelial function via amp-activated protein kinase. Science China Life Sciences. Science in China Press; 2018. p. 1024–9. 

7. Henriksen BS, Curtis ME, Fillmore N, Cardon BR, Thomson DM, Hancock CR. The effects of chronic AMPK activation on hepatic triglyceride accumulation and glycerol 3-phosphate acyltransferase activity with high fat feeding. Diabetol Metab Syndr. BioMed Central; 2013;5:29. 

8. Benton D, Young HA. Reducing Calorie Intake May Not Help You Lose Body Weight. Perspect Psychol Sci [Internet]. SAGE Publications Inc.; 2017 [cited 2020 Jun 28];12:703–14. Available from: /pmc/articles/PMC5639963/?report=abstract

9. Ackerman KE, Holtzman B, Cooper KM, Flynn EF, Bruinvels G, Tenforde AS, Popp KL, Simpkin AJ, Parziale AL. Low energy availability surrogates correlate with health and performance consequences of Relative Energy Deficiency in Sport. Br J Sports Med [Internet]. BMJ Publishing Group; 2019 [cited 2020 Aug 16];53:628–33. Available from:

10. Willoughby D, Hewlings S, Kalman D. Body composition changes in weight loss: Strategies and supplementation for maintaining lean body mass, a brief review [Internet]. Nutrients. MDPI AG; 2018 [cited 2021 May 10]. Available from: /pmc/articles/PMC6315740/

11. Dulloo AG, Jacquet J, Montani JP. How dieting makes some fatter: From a perspective of human body composition autoregulation. Proceedings of the Nutrition Society. 2012. p. 379–89. 

12. Westerterp KR. Control of energy expenditure in humans. European Journal of Clinical Nutrition. Nature Publishing Group; 2017. p. 340–4. 

13. Higginson AD, McNamara JM. An adaptive response to uncertainty can lead to weight gain during dieting attempts. Evol Med Public Heal [Internet]. Oxford University Press; 2016 [cited 2021 May 10];2016:369–80. Available from: /pmc/articles/PMC5139007/

14. Moro T, Tinsley G, Bianco A, Marcolin G, Pacelli QF, Battaglia G, Palma A, Gentil P, Neri M, Paoli A. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. J Transl Med. BioMed Central Ltd.; 2016;14. 

15. Tinsley GM, Moore ML, Graybeal AJ, Paoli A, Kim Y, Gonzales JU, Harry JR, Vandusseldorp TA, Kennedy DN, Cruz MR. Time-restricted feeding plus resistance training in active females: a randomized trial. Am J Clin Nutr [Internet]. 2019 [cited 2020 May 21];110:628–40. Available from: https://academic.oup.c

16. Jane L, Atkinson G, Jaime V, Hamilton S, Waller G, Harrison S. Intermittent fasting interventions for the treatment of overweight and obesity in adults aged 18 years and over: a systematic review protocol. JBI database of systematic reviews and implementation reports. JBI Database System Rev Implement Rep; 2015. p. 60–8. 

17. Li G, Xie C, Lu S, Nichols RG, Tian Y, Li L, Patel D, Ma Y, Brocker CN, Yan T, et al. Intermittent Fasting Promotes White Adipose Browning and Decreases Obesity by Shaping the Gut Microbiota. Cell Metab. Cell Press; 2017;26:672-685.e4.

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