Fasting And Metabolic Health
Metabolic Health
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Does Fasting Boost Metabolism?

Does Fasting Boost Metabolism?

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.

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. Also know about prediabetes diet.

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:

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.

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.

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.

How to intake Carbohydrate 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:

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.

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.

What can you eat while fasting?

The food you can eat when you are not fasting can be the food that you eat normally. Of course, there are certain restrictions that are to be followed like not indulging in sugary foods or fatty and oily foods. 

  • Drink a lot of fluids like water, tea, green tea, lemonade (without sugar), etc to prevent dehydration and supply your body with electrolytes and water. Replenish all the necessary water in these forms since the other supplies like – food, soups, etc will be restricted due to the fasting. 
  • Include foods from all food groups but make sure to not go overboard or excessively indulge in one group. Maintain a balanced diet. 
  • Foods with an overall low glycemic index like – yogurt, mushrooms, almonds, milk, fruits, etc are important during fasting
  • Whole wheat pasta, roti, or bread are a good idea with leafy vegetables. 
  • Foods that are power-packed like – nuts and seeds, paneer, makhana, etc would be highly beneficial. 

Tips for fasting

  • One most important thing to keep a check on during the fasting periods would be hypoglycemia and the cycles it ensues. To avoid hypoglycemia, usually, people cut down on the insulin dose, which might result in high blood sugars and/or DKA. Therefore, keep monitoring your blood sugars regularly, especially in the beginning until your body gets used to the new routine
  • Dehydration can also be risky as a person with diabetes needs to make sure to drink lots of water to be able to pass out the toxins during urination. Additionally, several kidney-related complications are also associated with diabetes. Having more water, even during fasting can provide the kidney with the desired level of water intake.
  • Start your fast with food categories that have a low GI. This means that the food will be slowly absorbed into the bloodstream resulting in a balanced (not spiked) increase in blood sugars. Fruits and salads with high fiber levels should be included in the diet so that they fill you up well and you are able to maintain the course of the fast.
  • Breaking the fast should include some but small quantities of foods with sugar or some fat. This will help gain the required energy without causing any harm.
  • Consult your physician before you engage in fasting so that you will be able to adjust the doses of insulin injections or medication according to the calorie and carb intake. 
  • Be mindful of any kind of strenuous physical activity that you would be undertaking at the time of fasting. Physical activities burn the extra glucose in the body leading to a higher risk of hypoglycemia. 

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. Also know about fasting blood sugar level.


What do you eat when fasting? 

Eat a lot of foods that have a low glycemic index like – yogurt, almonds, leafy vegetables, etc. These will give you the energy you require without raising the blood sugars. Eat a balanced diet including foods from all food groups – proteins, carbs, vitamins, minerals, etc to provide well-rounded nutrition to the body.

Why do people fast?

People fast due to different reasons – 

  1. To reduce weight
  2. Religious purposes
  3. Health conditions 
  4. Cleanse or purify the blood
  5. Specific days dedicated to certain Gods or Goddesses 
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This website's content is provided only for educational reasons and is not meant to be a replacement for professional medical advice. Due to individual differences, the reader should contact their physician to decide whether the material is applicable to their case.