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.
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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.
Intermittent fasting (IF or IMF) involves restricting food intake to specific times . 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 .
The most common schedule for IF is 8 hours of eating followed by 16 hours of fasting . This is called the 16:8 protocol and is an example of daily time-restricted fasting . 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 .
Let's explore what IF clinical research has demonstrated and answer some common IF questions.
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 . 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 . 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 .
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 . 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.
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 . According to studies conducted on mice on a calorie-restricted diet, this weight loss approach improves health and lengthens life span . 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].
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].
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.
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 .
Numerous studies have explored the relationship between IF and sleep quality but did not reveal any significant effects . 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 .
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 . The AHA Council for Obesity offers the following recommendations to help you eat intentionally :
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.
Everlywell offers access to telehealth for weight management online, which can connect you with a qualified healthcare provider. You can discuss your weight loss goals based on your availability from the comfort of your home.