Can changes in dietary habits help in improving your metabolic health? Various studies conclude that fasting does help in enhancing overall wellbeing which also includes metabolic health. Fasting helps in maintaining your glycemic levels, improving insulin sensitivity, reducing insulin resistance and thus enabling weight loss. But before we get into the workings of the overall metabolic functioning of your body, lets start with the basics.

What is Fasting?

Fasting can be defined as a duration of voluntary abstinence or restraint from food and drink.  Fasting can be done by either reducing the amount of food you eat, or by restricting the intake of calories in that particular duration. Fasting has been a practice throughout human evolution right from the time of hunter-gatherers. Just like we have evolved to be in sync with the circadian rhythm (day/night cycle), our metabolism also has adapted to daytime food and night time sleep.

There are a number of reasons for an individual to adopt a fasting regime - to lose weight, for religious/spiritual reasons or just as a lifestyle strategy to improve your health. Although, every person performs fasting in his or her own way, finding an eating pattern that suits you and your reasons for doing it may sometimes not be what's best for you. So to decide on which approach might be the right fit for you, lets learn about the various types of fasting.

What are the Types of Fasting?

There are many types of dietary approaches that involve interspacing planned periods of fasting with regular eating. Some of the most popular and effective types of fasting are as elaborated in the table below.

Type Method Example
Intermittent Fasting OR 16:8 Diet Fast for 14 to 16 hours a Day and limit your eating window to 8 to 10 hours. Based on your preference, you can consume two to three meals within this eating window. A 16 hour fasting window would be like if you eat your dinner at 8 pm on Monday and fast until your next meal at 12 pm noon on Tuesday.
Periodic Fasting OR 5:2 Diet Restricting your calorie intake 500 - 600 kcals for 2 days in the week and eating normally the other 5 days. Eat small meals not more than 600 kcals on Tuesdays & Fridays.Continue eating regular meals on the other 5 days.
Eat Stop Eat OR 24-Hour Fasting 24-hour Fasts Once or Twice a Week. A 24 hour fasting window would be like if you eat your dinner (last meal) at 8 pm on Monday and fast until your next meal at 8 pm on Tuesday.
Alternate-day Fasting Fast every other day by restricting quantity of either consumption or calories to less than 600 kcals. Eat your regular meal on Monday, restricted calorie intake to 500 kcals on Tuesday, and go back to eating a regular meal on Wednesday.
Extended Fasting It is a form of intermittent fasting that involves an extended pause on eating, typically lasting for 2 days/48 hours or more. Eat your lunch at 2 pm (last meal) on Monday, and stop eating or start the fast from that same Monday evening until your next meal 48 hours later on Wednesday evening. While this fast involves eliminating foods that contain calories, it is still extremely important to drink plenty of noncaloric fluids, such as water, throughout the fast to keep the body hydrated.

Remember, fasting affects people with underlying conditions differently. If you have Prediabetes or Type 2 Diabetes, talk to your care provider or coach before making dramatic changes to your diet. If you take insulin or are on blood sugar-lowering medications, it is even more critical to check with your doctor before engaging in any type of fasting, as it can plummet your blood-sugar to dangerously low levels and drastically alter how your medications work.

To learn more about Intermittent Fasting, Do's and Don'ts or how to pick the type of fast best suited to you, check out our article on Intermittent Fasting and Diabetes.

What are the Benefits of Fasting?

There are multiple benefits of Fasting. Some of them are:

  1. Weight Loss : Fasting may lead to weight loss due to two primary reasons. First, it restricts the intake of calorie, thus allowing the body to use its fat reserve. Second, it maintains a low level of insulin, thereby keeping the body in a fat-burning mode. It helps in shredding both your muscle and fat mass. Practicing it for a significant period may result in reducing the resting metabolic rate and assist in weight loss. When combined with resistance training, it decreases fat mass and improves health-related biomarkers. It also helps in reducing your appetite by maintaining Ghrelin levels which is a "hunger hormone" that tells you when to eat.
  2. Metabolic Flexibility : The body stores energy in the form of glycogen and fats. In high blood sugar levels, your cells use a part of this energy and stores the remaining portion in the liver or muscles in the form of fat or glycogen. During fasting, there is a depletion in glycogen reserve and the body switches to fat for energy. These fats are converted into fatty acids and then to ketones to produce energy. Using ketone bodies instead of blood glucose for energy may improve organ function, neural health, and overall muscle function. Switching between the fed and fasting state makes your body more metabolically flexible. During fed-state, the primary energy source would be glucose, while during the fasting state, your body uses fat as fuel. More the metabolic flexibility, more the fat burn after a heavy-fat meal.
  3. Insulin Sensitivity : A comprehensive research study assessing the long‐term effects of reduced intake on energy, states that calorie restriction reduces various cardiometabolic risk factors and significantly improves your insulin sensitivity index. Time-restricted eating helps in maintaining the circadian rhythm. Just changing the timing of meals, by eating earlier in the day and extending the overnight fast, significantly benefits metabolism. While a disruption in circadian rhythm may result in abnormal glucose metabolism and insulin resistance.

Managing Carbohydrate intake while Fasting

You should monitor your glucose intake to get the best out of fasting. Aim for a low glycemic diet to improve metabolic flexibility. Some of the measures that may help you in strictly restricting your glucose uptake are:

  1. Breaking your Fast : Your hunger hormone called Ghrelin can make you crave for glucose or sugar, especially in the initial days of starting the diet. On eating, this can suddenly raise your sugar levels and cause even more food craving and irritability. So it is essential to choose a meal that does not cause this surge in your blood glucose. Limit the hours of the day when you eat, and for best effect, make it earlier in the day (between 7 am to 3 pm, or even 10 am to 6 pm, but definitely not in the evening before bed and avoid snacking or eating at night-time.
  2. Monitor your Diet : Many people eat a heavy carbohydrate diet just before their fasting window. Avoid doing this as this takes more time for the body to switch to fat-based fuel. Avoid sugars and refined grains, and eat fruits, vegetables, beans, lentils, whole grains, lean proteins, and healthy fats instead. Let your body burn fat between meals. Don’t snack and be active throughout your day.

Bottom Line

Eating healthy is simple, but it can be incredibly hard to maintain. At the end of the day, there is no one-size-fits-all solution when it comes to nutrition. If you feel good when fasting and find it to be a sustainable way of eating, it can be a very powerful tool to lose weight and improve your health. Along with fasting, exercising and taking care of your sleep are also important factors to focus on, so the best diet for you is the one you can stick to in the long run.