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
Clinical research on intermittent fasting is limited—and mixed. Some studies have shown that it can lead to improved health and mild or moderate weight loss. Others suggest that fasting has no significant long-term health benefits.
How much weight can you lose in a month with intermittent fasting? ›
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 intermittent fasting enough to lose weight? ›
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.
Why am I not losing weight on 16:8 fasting? ›
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 till you see weight loss with intermittent fasting? ›
But the time it takes to see results can vary depending on individual factors such as starting weight, eating habits, and exercise routine. Many people begin to see some results within the first few weeks of starting intermittent fasting. This can include weight loss, increased energy, and improved mental clarity.
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).
What is the best intermittent fasting window to lose belly fat? ›
A 2023 review of research found that the 16/8 method and 16/8 combined with restricting calories were effective strategies for weight control in adults with overweight or obesity. An eating window starting before noon led to greater weight loss than one that began after noon.
Why is 16 hours the magic number for fasting? ›
While both 12-hour and 16-hour fasting can promote fat burning, it's possible that a 16-hour fast may be more effective. This is because the longer fasting period may lead to a greater depletion of glycogen stores, which can trigger higher levels of fat burning.
Does fasting help lose belly fat? ›
Fasting is a powerful tool for targeting and reducing belly fat. It works by shifting your body's metabolism from burning sugar to burning fat as its primary source of energy. This metabolic shift is what leads to fat loss, particularly in the abdominal area.
What to expect after 2 weeks of intermittent fasting? ›
Things to consider
It may take 2 to 4 weeks for your body to get used to eating on an intermittent fasting schedule. During those first few weeks, you may have headaches and feel hungry, grouchy, or tired. Know you may feel this way before you start and make a plan to push through these feelings.
A person needs to decide on and adhere to a 12-hour fasting window every day. According to some researchers, fasting for 10–16 hours can cause the body to turn its fat stores into energy, which releases ketones into the bloodstream. This should encourage weight loss.
Why am I gaining weight on intermittent fasting? ›
Going too long without eating might actually encourage your body to start storing more fat in response to starvation. Mattson's research shows that it can take two to four weeks before the body becomes accustomed to intermittent fasting. You might feel hungry or cranky while you're getting used to the new routine.
Can I eat whatever I want while intermittent fasting and still lose weight? ›
It's not a diet, so unless you have individual dietary restrictions, you can eat whatever you want within the eight-hour time frame. But the plan will work best for weight loss if you are already making smart, nutrient-rich choices, said NBC News health and nutrition editor Madelyn Fernstrom, Ph.
Does coffee break a fast? ›
Technically speaking, eating or drinking any calories breaks a fast. That means it's generally considered OK to drink black, unsweetened coffee or tea, as well as water.
Should I intermittent fast every day? ›
Fasting on either a daily or weekly basis helps your body burn fat. There are different approaches to intermittent fasting but the most popular include: Alternate day fasting includes normal eating every other day, with days of restricted eating (500 calories) in between.
What happens after 1 month of intermittent fasting? ›
Many people begin to notice intermittent-fasting results, such as improved gut health, focus, and energy, in just a few days. If your goal is weight loss, you may begin to notice changes in your body in as little as ten days, with noticeable weight loss in the first month.
What are the results of 30 days of intermittent fasting? ›
Men and women often experience an average weight loss of 1–2 pounds per week with intermittent fasting. That means you could lose 4–8 pounds in 30 days. Furthermore, studies show that typical weight loss with intermittent fasting is 7–11 pounds over the course of ten weeks.
How much weight can you lose with intermittent fasting in 2 weeks? ›
Effective Diet Plans for Rapid Weight Loss
| Diet Plan | How much can I lose in 2 weeks? | Example |
|---|
| Low-carb diet | 5-10 pounds | Atkins, Ketogenic |
| Low-fat diet | 3-6 pounds | Ornish, Pritikin |
| Intermittent Fasting | 4-8 pounds | 16/8 method, Eat-Stop-Eat |
Sep 23, 2023
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.
Can I lose 30 pounds in 3 months with intermittent fasting? ›
Yes. 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.
