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Surprising Updates on Intermittent Fasting

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Intermittent fasting is a dietary pattern that alternates periods of eating with periods of fasting. During the fasting periods, only water or other non-caloric beverages are consumed. There are several types of intermittent fasting, including time-restricted feeding, alternate-day fasting, and modified fasting. The practice of intermittent fasting has existed for centuries, with some religious and cultural traditions incorporating periods of fasting into their practices.

In recent years, intermittent fasting has gained popularity as a potential weight-loss strategy and for its associated health benefits. Studies have shown that intermittent fasting can improve insulin sensitivity, lower blood sugar levels, reduce inflammation, and promote weight loss. Additionally, intermittent fasting may have neuroprotective effects and improve cognitive function.

The popularity of intermittent fasting has led to increasing interest and research into its effects on overall health and disease prevention. As more people take up this approach, we must pay attention to its potential benefits as well as any risks involved. In the following sections, we will delve deeper into the different types of intermittent fasting, the science behind the practice, who can benefit from it, and guidelines for getting started.

Types of Intermittent Fasting

Time-Restricted Feeding

Time-restricted feeding is one of the most popular methods of intermittent fasting. It involves eating during a specific time window and fasting for the rest of the day. The most common approach to time-restricted feeding is the 16/8 method, where you fast for 16 hours and eat within an 8-hour window. During the eating window, you can have three meals or more.


  • Helps you lose weight by reducing calorie intake
  • Can improve insulin sensitivity and blood sugar control
  • May improve heart health by lowering blood pressure and cholesterol levels


  • Difficult to sustain in the long run
  • Possible to overeat during the eating window, leading to weight gain
  • May disrupt social life if the eating window does not coincide with others

Alternate-Day Fasting

In alternate-day fasting, you fast every other day. On the fasting day, you are allowed to eat 500-600 calories. On the non-fasting day, you can eat normally.


  • May aid in weight loss, especially in obese people
  • Can reduce inflammation and improve blood lipid profile
  • May improve insulin sensitivity and blood sugar control


  • May lead to overeating on non-fasting days
  • Difficult to sustain in the long run
  • May affect social life if meals have to be adjusted on fasting and non-fasting days

Modified Fasting

Modified fasting is a more flexible approach to intermittent fasting. It involves eating only a limited amount of calories on fasting days or avoiding certain types of food altogether. One example of modified fasting is the 5:2 diet, where you eat normally for five days and eat 500-600 calories for two non-consecutive days.


  • May aid in weight loss, especially in obese people
  • May reduce inflammation and improve blood lipid profile
  • May improve insulin sensitivity and blood sugar control


  • Can be challenging to follow, especially in social situations
  • May lead to overeating on non-fasting days
  • May cause fatigue and low energy levels on fasting days

The Science Behind Intermittent Fasting

Intermittent fasting (IF) has become a popular topic of discussion in the field of health and wellness. Unlike traditional dieting, which focuses on restricting calories and specific food groups, IF is all about controlling when you eat. Essentially, it involves limiting the number of hours per day or days per week that you consume food.

Explanation of How Intermittent Fasting Affects the Body

When you fast, your body enters into a state of ketosis. This means that it starts to burn fat for energy instead of glucose. When the body burns fat, it produces ketones, which are molecules that provide energy to your brain and body. Studies have shown that this can lead to a range of benefits.

Benefits for Metabolism

Insulin Sensitivity

Insulin is a hormone that regulates glucose levels in the blood. When you eat, your body releases insulin to absorb glucose. High levels of insulin can lead to insulin resistance, a condition that is associated with type 2 diabetes and other health concerns. Research has found that IF can improve insulin sensitivity by reducing insulin levels in the body, which can reduce the risk of insulin resistance and related health problems.

Blood Sugar Levels

IF may also help regulate blood sugar levels. A study conducted on type 2 diabetic patients found that those who followed an IF diet experienced a decrease in their fasting blood sugar levels. This is due to the fact that fasting reduces the need for insulin, which helps lower blood sugar levels. This improvement in blood sugar control can also help reduce the risk of complications associated with diabetes, such as heart disease and kidney damage.

Benefits for Weight Loss

Explanation of How Intermittent Fasting Helps in Weight Loss

Intermittent fasting is one of the most effective ways to lose weight. This is because it restricts calories and lowers insulin levels, both of which are crucial for weight loss. When you fast, your body’s fat-burning capacity is enhanced, and your metabolism increases, allowing you to burn more calories than you consume. The reduction in calorie intake can lead to weight loss, especially when combined with a healthy diet and regular exercise.

Scientific Studies Proving the Effectiveness of Intermittent Fasting for Weight Loss

Several studies have found that IF can lead to significant weight loss. One study published in the Journal of Nutrition found that following an IF diet for eight weeks lead to an average weight loss of 8 pounds. Another study conducted on obese adults found that a 12-week IF diet resulted in a 7% reduction in body weight. While more research is needed to fully understand the long-term effects of IF on weight loss, these studies suggest that it is a promising approach for managing weight.

Who Can Benefit from Intermittent Fasting?

Intermittent fasting has become an increasingly popular method for managing weight, improving metabolic health, and overall wellness. However, it may not be suitable for everyone. Let's explore who can benefit from intermittent fasting and who should avoid it.

Health Conditions Where Intermittent Fasting is Not Recommended

Eating Disorders

Intermittent fasting involves controlling the number of hours you eat, which can trigger those with eating disorders, especially those who struggle with anorexia or bulimia. Individuals with eating disorders should avoid intermittent fasting.


Intermittent fasting may lower blood sugar levels, which can be beneficial for people with diabetes. However, it may also increase the risk of hypoglycemia (low blood sugar) in diabetics who are using insulin or other blood sugar-lowering medications. As such, people with diabetes should speak to their healthcare provider before trying intermittent fasting.


Individuals who are pregnant, breastfeeding, or have a history of heart disease should also consult with their doctor before starting an intermittent fasting plan.

People Who Can Benefit from Intermittent Fasting

Healthy Individuals

Intermittent fasting has numerous health benefits. It can help control weight, improve metabolic health, and could help prevent chronic disease. Healthy individuals who are looking to improve their overall wellness can also benefit from intermittent fasting. By having a controlled eating window, the body is less likely to be in a constantly fed state, which may help reduce inflammation and oxidative stress.

Overweight Individuals

Intermittent fasting is particularly beneficial for people who are struggling with their weight. By reducing the number of hours you eat, you also reduce the number of calories you consume, leading to weight loss. Intermittent fasting also helps to reduce visceral fat, which is a type of fat that is stored in the abdominal cavity and is associated with an increased risk of diabetes and heart disease.

How to Start Intermittent Fasting

Guidelines to Follow

Before starting an intermittent fasting plan, it's essential to consider the following guidelines:

Safety Guidelines

  • Consult your healthcare provider before starting an intermittent fasting plan if you have an underlying medical condition.
  • Make sure to stay hydrated and drink lots of water during the fasting phase.
  • Do not over-exercise during a fasting window, especially during extended fasts, and do not push your body over its limits.
  • Discontinue your intermittent fasting plan if you experience any adverse side effects.

Food Choices and Composition

Intermittent fasting is not just about when you eat but also what you eat and how much you eat. During your feeding window, it's essential to choose nutrient-dense foods that provide enough energy and nutrients to support your everyday activities.

  • Eat a balanced diet that consists of lean protein, complex carbohydrates, and healthy fats.
  • Avoid processed foods, sugary drinks, and foods high in saturated fats and calories.
  • It's also essential to follow portion sizes, especially during the feeding window, to avoid overeating.
  • The timing of your feeding window depends on various factors, including your lifestyle, work schedule, and health status. So, it's essential to find a schedule that works best for you.

Common Mistakes to Avoid

Overeating During the Feeding Window

A common mistake that people make while practicing intermittent fasting is overeating during the feeding window. Instead of consuming fewer calories, they tend to consume more calories than they would regularly consume in a day. Overeating during the feeding window can counteract the benefits of intermittent fasting and lead to weight gain. To avoid overeating, it's essential to plan meals that are satiating and filling, but also have enough nutritional value to support the fast.

Not Consuming Enough Water

During the fasting period, it's essential to stay hydrated and drink enough water. Water intake plays a vital role in the body's metabolic processes, and not drinking enough water during the fasting period can lead to dehydration and other adverse effects. It's also crucial to consume enough fluids to help keep you feeling full and satisfied during the fasting period.

By following these guidelines and avoiding common mistakes, you can effectively incorporate intermittent fasting into your lifestyle, improve overall wellness, and achieve your health goals.


Intermittent fasting can be an effective and safe way to improve your overall health and well-being. However, before starting an intermittent fasting plan, it is crucial to consult with a healthcare provider to assess your current health status and ensure that intermittent fasting is appropriate for you.

It's also essential to listen to your body and make adjustments if needed. While intermittent fasting can be beneficial, it is not for everyone. It's crucial to pay attention to any adverse side effects, such as headaches, dizziness, or fatigue, and discontinue the intermittent fasting plan if these symptoms persist.

To achieve the most benefits from intermittent fasting, it's also essential to maintain a healthy and balanced diet and ensure that you're getting enough nutrients, fiber, and hydration during the feeding window. Planning your meals in advance, limiting processed foods and sugary drinks, and focusing on whole, nutrient-rich foods can help you make the most out of your intermittent fasting plan.

Future research and potential advancements in intermittent fasting

Intermittent fasting has gained popularity in recent years, and many studies have proven its effectiveness in improving health and preventing chronic conditions. However, more research is needed to explore the impact of intermittent fasting on different populations and to investigate potential long-term effects.

Future studies may also examine how various types of intermittent fasting, including modified fasting and time-restricted feeding, impact the body's metabolism and health outcomes. Additionally, researchers may explore how intermittent fasting can be combined with other lifestyle changes, such as exercise, to maximize benefits and improve overall health.

William H. McDaniel, MD

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School.

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