Bathroom scale and measuring tape for checking on weight loss with intermittent fasting

Does intermittent fasting work?

Written on February 3, 2023 by Theresa Vuskovich, DMD. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

Table of contents

In recent years, intermittent fasting has gained popularity as a weight loss strategy. But does intermittent fasting work? The answer depends on your health goals, lifestyle choices, health conditions, and dedication. This article explains intermittent fasting and whether it is effective for losing weight and improving your overall health.

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What is intermittent fasting?

Intermittent fasting (IF or IMF) involves restricting food intake to specific times [1]. During an IF diet, you eat for a limited number of hours each day or only on certain days [1,2]. Alternate-day fasting, whole-day fasting, and time-restricted feeding are the three most popular intermittent fasting protocols [2].

The most common schedule for IF is 8 hours of eating followed by 16 hours of fasting [1]. This is called the 16:8 protocol and is an example of daily time-restricted fasting [1]. Many clinical studies have examined IF protocols for weight loss and disease prevention, but more clinical studies are required to see if IF works [2,5]. The current results come from short-term studies with few participants [3].

Let's explore what IF clinical research has demonstrated and answer some common IF questions.

Will intermittent fasting help you lose weight?

Maybe. However, IF alone will not lead to losing weight. You still need to eat a healthy whole-food diet, exercise regularly, and limit your daily calorie intake to lose weight [4]. Since your food intake is restricted during IF, IF may help you lose weight if it helps you reduce your overall calorie intake.

A recent study in the New England Journal of Medicine found that time-restricted eating was not more effective than calorie restriction alone in reducing body weight for adults with obesity [5]. During the 12-month trial, the 139 participants were randomized into two groups. One group used a time-restricted feeding schedule to consume the same amount of calories as the other group. Compared to the calorie-restricted group, IF participants did not lose additional weight or experience any additional health benefits such as reductions in blood pressure, glucose levels, and total body fat [5].

Another study published in 2023 in the Journal of the American Heart Association called the Daily24 Cohort study found that the frequency of meals is more predictive of weight gain than meal timing [6]. Rather than limiting eating hours when you are concerned about weight gain, limiting how often you eat large meals is best. Traditional calorie counting might lead to the best long-term weight management results.

Will intermittent fasting improve your health?

Maybe. However, IF alone will not lead to better health. You will need to maintain an active lifestyle and a balanced diet. IF and calorie-restricted eating originated from animal studies showing health benefits [7]. According to studies conducted on mice on a calorie-restricted diet, this weight loss approach improves health and lengthens life span [7]. Yet, the potential benefits of IF and a calorie-restricted diet remain unclear in humans. Let's explore what the research reveals about the effects of IF on heart health, blood sugar, and sleep [8-12].

Blood pressure

High blood pressure has been linked to increased heart disease and stroke risk. Maintaining a blood pressure of less than 130/80mm/Hg can reduce your risk of developing heart disease. Can IF improve your blood pressure? Possibly. Multiple studies have demonstrated IF or other calorie-restricted diets improved the blood pressure of adults with obesity who lost approximately 6% of their body weight [8,9].

Triglycerides

A triglyceride is a type of fat found in your blood. High triglyceride levels are associated with heart disease. Multiple studies have also demonstrated IF may improve triglyceride levels in people with obesity [8-10]. As with blood pressure, IF only improves triglyceride levels if you lose weight [8-10]. The IF diet requires continuous dedication, and staying on track long-term is often challenging.

Blood sugar

The current obesity and diabetes epidemic have resulted in numerous studies investigating whether IF can help people with obesity and diabetes [8-10]. The studies discovered the 5:2 IF approach, which entails eating normally for five days a week and restricting your calorie intake to 500–600 calories on the other two, may improve fasting plasma glucose levels [8,9]. The American Diabetes (ADA) advocates a balanced diet and acknowledges that additional studies are needed to confirm IF's benefits for adults with diabetes and prediabetes [11].

Sleep

Numerous studies have explored the relationship between IF and sleep quality but did not reveal any significant effects [13]. However, a lack of sleep can significantly impact your weight and ability to lose weight [12,13]. With Everlywell's at-home sleep and stress test, you can better understand your sleep patterns and stress levels. Getting better sleep may improve your ability to lose weight [12].

IF is not the magic solution for your weight loss or health goals. The American Heart Association (AHA) recommends an "intentional approach to eating," which may include IF as an approach to weight loss [9]. The AHA Council for Obesity offers the following recommendations to help you eat intentionally [9]:

  • Control your portion sizes and manage your hunger with planned meals and snacks
  • Introduce more healthy foods to your diet
  • Plan your day's calories according to a defined schedule
  • Consider intermittent fasting as an option for reducing calorie intake and body weight

If you are an adult with obesity or are overweight, IF may improve your blood pressure, lipid profile, and glucose sensitivity [8,9]. More studies are needed to confirm the benefits of IF in people with and without obesity. You may lose weight by using IF when it is mentally beneficial to set eating hours, resulting in lower calorie intake.

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References

  1. Li Z, Heber D. Intermittent Fasting. JAMA. 2021;326(13):1338. doi:10.1001/jama.2020.15140. URL.
  2. Tinsley GM, La Bounty PM. Effects of intermittent fasting on body composition and clinical health markers in humans. Nutr Rev. 2015;73(10):661-674. doi:10.1093/nutrit/nuv041. URL.
  3. Ostendorf DM, Caldwell AE, Zaman A, et al.. Comparison of weight loss induced by daily caloric restriction versus intermittent fasting (DRIFT) in individuals with obesity: study protocol for a 52-week randomized clinical trial. Trials. 2022;23(1). doi:10.1186/s13063-022-06523-2. URL.
  4. St-Onge MP, Ard J, Baskin ML, et al. Meal timing and frequency: Implications for cardiovascular disease prevention: A scientific statement from the American heart association. Circulation. 2017;135(9):e96-e121. doi:10.1161/CIR.0000000000000476. URL.
  5. Liu D, Huang Y, Huang C, et al.. Calorie Restriction with or without Time-Restricted Eating in Weight Loss. New England Journal of Medicine. 2022;386(16):1495-1504. doi:10.1056/nejmoa2114833. URL.
  6. Zhao D, Guallar E, Woolf TB, et al.. Association of Eating and Sleeping Intervals With Weight Change Over Time: The Daily24 Cohort. Journal of the American Heart Association. 2023. doi:10.1161/jaha.122.02648. URL.
  7. Robertson LT, Mitchell JR. Benefits of short-term dietary restriction in mammals. Exp Gerontol. 2013;48(10):1043-1048. doi:10.1016/j.exger.2013.01.009. URL.
  8. Patikorn, C., Roubal, K., Veettil, S.K., Chandran, V., Pham, T., Lee, Y.Y., Giovannucci, E.L., Varady, K.A., Chaiyakunapruk, N., 2021. Intermittent Fasting and Obesity-Related Health Outcomes. JAMA Network Open 4, e2139558.. doi:10.1001/jamanetworkopen.2021.39558. URL.
  9. St-Onge M-P, Ard J, Baskin ML, et al.. Meal Timing and Frequency: Implications for Cardiovascular Disease Prevention: A Scientific Statement From the American Heart Association. Circulation. 2017;135(9):e96-e121. doi:10.1161/cir.0000000000000476. URL.
  10. Meng H, Zhu L, Kord-Varkaneh H, O Santos H, Tinsley GM, Fu P. Effects of intermittent fasting and energy-restricted diets on lipid profile: A systematic review and meta-analysis. Nutrition. 2020;77(110801):110801. doi:10.1016/j.nut.2020.110801. URL.
  11. ElSayed NA, Aleppo G, Aroda VR, et al. 5. Facilitating positive health behaviors and well-being to improve health outcomes: Standards of care in diabetes-2023. Diabetes Care. 2023;46(Supple 1):S68-S96. doi:10.2337/dc23-S005. URL.
  12. Papatriantafyllou E, Efthymiou D, Zoumbaneas E, Popescu CA, Vassilopoulou E. Sleep deprivation: Effects on weight loss and weight loss maintenance. Nutrients. 2022;14(8):1549. doi:10.3390/nu14081549. URL.
  13. McStay M, Gabel K, Cienfuegos S, Ezpeleta M, Lin S, Varady KA. Intermittent Fasting and Sleep: A Review of Human Trials. Nutrients. 2021;13(10):3489. URL. Published 2021 Oct 1. doi:10.3390/nu13103489.
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