Depending on the fasting method a person practices, it may be possible to consume some foods and drinks.
Fasting is a dietary practice where people do not consume food or beverages that contain calories for a certain period.
Some people may fast for a certain number of hours per day, while others may fast over a 24–48 hour period or even longer.
There are many different kinds of fasting, while certain food and drinks may be less likely to break a fast than others, depending on the fasting diet a person practices.
This article explores what fasting is and its benefits, different forms of fasting, and the food and beverages that people may wish to include or avoid when fasting.
Fasting is a dietary practice where people voluntarily avoid consuming food and drink containing calories for a set period.
People have practiced varied fasting approaches for hundreds of years. There are many different fasting methods that people may follow, including a wide range of religious fasts.
A 2015 systematic review found evidence that this practice may positively impact health in a variety of ways.
Rodent studies suggest that fasting improves metabolism and reduces the risk of:
Meanwhile, human studies support the idea that fasting can reduce obesity, with participants experiencing weight loss across a wide range of experiments.
However, there is limited evidence to suggest fasting promotes more weight loss than other dietary programs that restrict a person’s daily calories.
While there are many different forms of fasting, people can choose the method that best suits their needs. Some examples of fasting methods are below.
Complete alternate day fasting
This form of fasting involves alternating fasting days with eating days.
During fasting days, people will tend to avoid consuming food and drink that contains energy or calories.
On eating days, they can consume as much calorie-containing food and beverages as necessary.
This form of fasting involves alternate days of fasting and eating.
On fasting days, people will typically only consume 20–25% of their calorie needs and consume as many calories as they need on eating days.
A popular version of this form of fasting is the 5:2 diet.
People who follow this diet fast for two nonconsecutive days per week.
Intermittent fasting involves restricting the window in which a person can eat to a few hours per day.
For example, some people may have an eating window of between 12–6 p.m. and fast outside of these hours.
Ramadan is a holy month that people following Islam celebrate. During Ramadan, individuals may fast between dawn and sunset.
A common dietary practice of Ramadan fasting is to consume a large meal after sunset and then a lighter meal before dawn.
Other religious fasts
People who follow other religions may take part in specific fasts.
For example, people following the Church of Jesus Christ of Latter-day Saints may not consume food or drink for extended periods.
Others who follow the Seventh-day Adventist Church may have their last meal in the afternoon and fast until the next morning.
For most people, anything they consume during a fast should have minimal or zero calories unless they are taking part in a modified fast, such as the 5:2 diet.
Water contains zero calories, meaning a person can drink as much of it as they wish during fasting periods.
Both still and sparkling water do not contain any calories. And while flavored water may not carry any calories, people may wish to check the beverage’s nutrition label before purchase or consumption.
Black coffee and tea
Black coffee contains very few calories per cup.
Research shows that caffeine can act as an appetite suppressant, which may make it easier for someone to stick to a fast.
Certain teas, such as green tea, can increase the feeling of fullness and decrease appetite.
Certain foods and supplements may increase a person’s likelihood of breaking their fast, including the below.
Branched-chain amino acids
Some people may take branched-chain amino acid (BCAA) supplements while fasting. Manufacturers label and market some of these as calorie-free or very low calorie.
However, most BCAA supplements actually contain 4 calories per gram.
BCAA supplements may show zero — or very low — calories due to a labeling loophole in supplement industry regulations.
FDA guidelines state, “Protein shall not be declared on labels of products that, other than ingredients added solely for technological reasons, contain only individual amino acids.”
This means that although BCAAs do contain calories, manufacturers will not list those calories on the packaging.
Additionally, research shows that leucine, a type of BCAA, serves as a signal to the brain that the body has not fasted.
Food and drinks that contain calories
Strictly speaking, any amount of calories will break a fast.
If a person follows a strict fasting schedule, they should avoid any food or drinks containing calories.
Those following a modified fasting diet can often eat up to 25% of their daily calorie needs while fasting.
With this in mind, it is important to know how many calories a person needs while avoiding food and drinks that exceed their total daily limit.
The National Institute of Diabetes and Digestive and Kidney Diseases have a free body weight planner that can help people calculate how many calories they need per day.
Some certain supplements and foods are generally within the limits of several fasting methods, including the below.
Some multivitamin brands do not contain any calories.
However, people may wish to check any nutritional labels or review the manufacturer’s website before purchasing.
It is worth noting that some individuals may find that consuming high concentrations of micronutrients may send signals to the body that someone is not in a fasted state.
For this reason, it may be best to consume multivitamins and other supplements during periods of eating.
Low calorie food and drink
Certain fasting diets, such as the modified fasting plan, allow people to eat a limited amount of calories on fast days, often up to 25% of their usual daily caloric intake.
For example, a person requiring 2,000 calories per day could consume up to 500 calories daily if they follow this method.
Some examples of lower calorie food and drinks include:
- lean meat
- unsweetened black coffee
- unsweetened tea with no milk
People often break their fast during Ramadan sweet foods, such as dates, before eating a main meal that may be high in carbohydrates.
Food and drink with low glycemic load
Consuming food low in glycemic load may make people feel full for longer and provide a gentle way to break a fast.
Food and drink that are low in glycemic load include:
- rolled or steel-cut oats
- nonstarchy vegetables
- sweet potatoes
- most fruits
High protein food and drink
High protein foods and beverages may help with satiety, allowing someone to feel full without eating so much that they shock their digestive system after a period without food.
High protein foods include:
- nuts, such as almonds
- nut butter, such as peanut, cashew, and almond
- dairy products, such as cheese and yogurt
- poultry, including chicken and turkey
- lean meats
- fish, including salmon and cod
- protein powders and shakes
Fasting may have health benefits, such as reducing body weight and lowering the likelihood of developing nonalcoholic fatty liver disease, diabetes, and cancer.
There are many different forms of fasting, and people can choose the type of fast that best suits their needs.
Some fasts require people to consume zero calories during fasting periods, while others allow individuals to consume a percentage of their daily caloric needs.
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