Is skipping meals a bad idea or a secret weight-loss weapon? One diet trend that shows no sign of going away soon is intermittent fasting. That's when you voluntarily abstain from food or beverages other than water for a certain amount of time. Some fasting is for religious reasons, while others fast for weight loss.
But is intermittent fasting a healthy way to lose weight?
The three popular approaches to intermittent fasting are:
- Alternate-day fasting
Eat a normal, healthy diet one day and then completely fast or have one small meal the next day. Usually, the small meal is fewer than 500 calories. - 5-2 fasting
Eat a normal diet five days a week and fast two days per week. - Daily time-restricted fasting
Eat normally but only within an eight-hour window each day. For example, skip breakfast, but eat lunch around 11 a.m. and dinner by 7 p.m.
Benefits of intermittent fasting
Can intermittent fasting improve your health? Recent research has found that using intermittent fasting for weight loss may have some benefits in the short term.
It appears that fasting for a short time can produce ketosis, which is a process that occurs when the body doesn't have enough glucose for energy, so it breaks down stored fat instead. This causes an increase in substances called ketones. This, coupled with fewer calories consumed overall, can lead to weight loss. Research suggests that alternate-day fasting is about as effective as a typical low-calorie diet for weight loss.
Fasting also affects metabolic processes in the body that may work to decrease inflammation, as well as improve blood sugar regulation and physical stress response. Some research shows this may improve conditions associated with inflammation like arthritis, asthma and multiple sclerosis.
Little long-term research has been done on intermittent fasting to examine how it affects people over time. As a result, long-term health benefits or risks are unknown.
Side effects of intermittent fasting
Intermittent fasting can have unpleasant side effects. They could include hunger, fatigue, insomnia, irritability, decreased concentration, nausea, constipation and headaches. Most side effects go away within a month.
Sticking with an intermittent fasting routine can be easier for some people rather than trying to watch calories every day. Other people, especially those with busy or variable schedules, have more difficulty maintaining an intermittent fasting routine.
Is intermittent fasting right for you?
Intermittent fasting is safe for many people, but it's not for everyone. Skipping meals is not recommended for people under 18, those with a history of disordered eating, or those who are pregnant or breastfeeding. Athletes may find it difficult to fuel and refuel appropriately for an active lifestyle. If you have diabetes or other medical issues, talk with your health care team before starting intermittent fasting.
Also, note that the key to weight loss with intermittent fasting is not to overeat during your eating windows. Eating fewer calories than you expend remains the basis for losing weight.
Shortening the eating window may make it difficult to get the vitamins and minerals you need. While on this diet, it is important to eat meals made from quality, healthy ingredients, such as fruits, vegetables, whole grains, low-fat dairy and lean protein.
Intermittent fasting can be dangerous if taken too far. A technique called dry fasting restricts food and fluid intake, resulting in severe dehydration and posing serious health concerns. Malnutrition can occur if the caloric restriction is too severe, such as averaging fewer than 1,200 calories a day long term.
Romi Londre is a dietitian in Nutrition in Eau Claire, Wisconsin.
FAQs
If you consistently stay active while following intermittent fasting, you can lose as much as 6-8 pounds per month. This estimation is shockingly high when you consider that all you have to do is not eat for select hours throughout the day.
Is it better to fast 12 or 16 hours? ›
A good rule of thumb for those wanting to fast to improve their metabolic and overall health is to leave at least 12 hours between meals – ideally more – on a regular basis, according to Dr Adam Collins, Principal Teaching Fellow in Nutrition at the University of Surrey.
What is the best intermittent fasting schedule for weight loss? ›
Depending on your lifestyle and when you can manage to stop eating, the best hours for intermittent fasting include the 16/8 or 14/10 fasting periods. Intermittent fasting is hailed by many as the new mantra of weight loss, disease prevention, and reversal of aging.
What are the basic rules for intermittent fasting? ›
How to practice intermittent fasting
- Eating during a 12-hour window every day (between 7 a.m. and 7 p.m., for example) and fasting for the other 12 hours.
- Eating during an 8-hour window every day (between 11 a.m. and 7 p.m., for example) and fasting for the other 16 hours.
If you've tried intermittent fasting but aren't losing weight, possible reasons why include overeating during your eating window and poor food choices. To help, you can try eating fewer calories, work on balancing your meals, or create a smaller or larger eating window.
How long does it take to lose 10 lbs intermittent fasting? ›
Weinandy says that results are usually apparent around the 10-week mark, adding that she sees an average weight loss of seven to 10 pounds over that period through any of the three approaches to intermittent fasting mentioned previously. It might take longer than that since everyone's metabolism works differently.
What can I drink while fasting? ›
Generally speaking, while fasting with time-restricted intermittent eating, you don't eat any food at all and only drink beverages with very few calories, such as water or unsweetened coffee and tea without milk. When you're not fasting, it's important to eat a healthy and varied diet that's good for your body.
Does sleep count as fasting? ›
The easiest way to do the 12-hour fast is to include the period of sleep in the fasting window. For example, a person could choose to fast between 7 p.m. and 7 a.m. They would need to finish their dinner before 7 p.m. and wait until 7 a.m. to eat breakfast but would be asleep for much of the time in between.
Does coffee break a fast? ›
Black coffee won't break your fast
For most people, the nutrients in 1–2 cups (240–470 ml) of black coffee aren't enough to initiate a significant metabolic change that would break a fast ( 3 , 4 ). Some people say that coffee suppresses your appetite, making it easier to stick with your fast in the long term.
How can I drop 20 pounds fast? ›
This can be done by either consuming less food, exercising more, or both. That said, while it's possible to lose 20 lbs in a month with a very low-calorie diet, this isn't the most sustainable way to lose weight and should only be attempted in consultation with your doctor.
The 20/4 fasting method is linked with cardiovascular improvements, such as reduced blood pressure and cholesterol levels. These changes directly contribute to a lower risk of developing heart disease, strokes, and other cardiovascular conditions, underscoring the heart health benefits of this fasting regimen.
How to lose belly fat with intermittent fasting? ›
Best Intermittent Fasting Method For Subcutaneous Belly Fat
- 16/8 Method: Fast for 16 hours and have an 8-hour eating window daily. ...
- 5:2 Method: With the 5:2 method, you consume your regular diet five days a week and consume around 500-600 calories for two remaining fasting days.
Foods and beverages that do not break a fast include water, black coffee, unsweetened tea, and diluted apple cider vinegar.
What is the golden rule of intermittent fasting? ›
The absolute most important rule is “Don't break your fast”.
Beware of foods labeled zero calories, as most will have trace amounts of calories that can break your fast if you eat enough. Drink lots of water, add a fiber source with your meals, or use a supplement to help manage hunger cravings.
How fast can I lose 30 pounds with intermittent fasting? ›
How much, though, depends on what kind of intermittent fasting schedule you're following (more on those schedules, below). People who do some form of full-day fasts usually lose about 10 to 30 pounds over a three-to-six-month period, says Varady.
Can I lose 20 pounds in 2 months with intermittent fasting? ›
Yes, intermittent fasting may help you lose 20 pounds in 2 months. This involves cycling between periods of eating and fasting. This can be an effective approach as it allows you to reduce your overall calorie intake while eating satisfying meals (5).
How long does it take for 16:8 intermittent fasting to work? ›
Additionally, it will take your body a while to get used to this new eating schedule. So don't expect results right away. You may need to wait between 2 and 4 weeks to see or feel any results.
