How Much Weight Can You Lose With Intermittent Fasting?

  • Medical Reviewer: Dany Paul Baby, MD
Medically Reviewed on 6/1/2022

What are the best schedules for IF? 

Intermittent fasting (IF) is a dieting technique where you focus on timing instead of counting calories. Studies show that you can lose between seven and 11 pounds after 10 weeks of intermittent fasting.
Intermittent fasting (IF) is a dieting technique where you focus on timing instead of counting calories. Studies show that you can lose between seven and 11 pounds after 10 weeks of intermittent fasting.

Intermittent fasting (IF) is a dieting technique where you focus on timing instead of counting calories. There are a few different timing schedules that you can try with IF. 

This means that there could be slight differences in how much weight you lose depending on what technique you try. Luckily, the main techniques studied so far lead to consistent weight with loss. 

An analysis of 40 different studies found an average loss of between seven and 11 pounds after 10 weeks of IF. Another analysis of 27 IF studies found an average weight loss of 0.8% to 13.0% of the participants’ starting weight within the relatively short time frames studied.   

In general, intermittent fasting refers to dividing your days into times when you can eat and times when you can’t, called a fasting interval. Since there are many different ways that you can do this, you should pick the schedule that works best for you. 

Common examples include: 

  • The 16/8 approach. This is when you fast for 16 hours a day and only let yourself eat during an eight-hour window. You can choose exactly when this window falls. Many people like to have it begin right after their normal dinner time and then continue while they sleep until they’re allowed a late breakfast. For example, you could only let yourself eat from 11 a.m. to 7 p.m.. Some people even cut their eating window down to 6 hours. 
  • The 5:2 approach. This is when you eat normally for five days of the week and then limit yourself to a single small meal on the remaining days. This meal should range from about 400 to 600 calories. You should spread your two fasting days out by at least one day of normal eating. 
  • Alternate day fasting. With this approach, you only eat food every other day. Research indicates that this method is less effective than the 16/8 and 5:2 approaches. This could be because fasting intervals that are 24 hours and up can trigger starvation responses in your body. This will cause your body to store fat instead of burning it. 
  • Moderate alternate day fasting. This is when you eat normally every other day and heavily restrict your calories on alternate days. It involves slightly more fasting than the 5:2 approach but less fasting than the traditional alternate day approach. 

It can be difficult to adjust to IF so some doctors recommend slowly extending your fasting window over the course of a few weeks. For example, you could start by only fasting for 10 hours a day and then add one hour of fasting time a week until you reach 16 or 18 hours. 

How should you eat and drink when you’re trying IF? 

When you’re fasting with IF you can only drink water and other zero-calorie beverages. Examples include black coffee and tea.

This diet can become problematic if you follow these fasting periods with heavy binging. You should only consume your regular number of calories during eating periods. Also, the diet is more effective if you limit your consumption of junk foods, processed foods, and high-calorie fast foods. 

If you’re looking to change your eating habits along with IF many experts recommend using the Mediterranean diet as a general guideline. This diet prioritizes whole grains, greens, and lean proteins. It also encourages practical substitutions like cooking with olive oil instead of butter. 

Keep in mind that the handful of studies that have tried to combine IF with traditional calorie counting methods don’t show an increase in weight loss. Both methods seem to be equally effective on their own but don’t create added weight loss benefits.

Why does intermittent fasting work? 

Experts believe that intermittent fasting is effective because it keeps us more in tune with the way that our bodies evolved. Traditional hunter-gatherer methods, which existed for minimally tens of thousands of years before the advent of farming, frequently involved extended periods between meals. 

In contrast, the average American diet includes consistent eating across a 14-hour time frame each day. People usually include three meals a day with snacking in between. This allows your body to survive off of the calories that you put into your stomach each day. It’s only when you run out of these calories that your body starts burning fat. 

The theory behind IF is that it gives your body a longer time between meals than the average American diet. You’ll need to use the energy in your stored fat when you run out of recently eaten calories. 

Who should avoid intermittent fasting? 

Intermittent fasting is a safe diet choice for most healthy individuals. But it isn’t safe for everyone. People who shouldn’t try IF include: 

  • Children and young adults who are younger than 18, because they’re still actively growing and have different caloric needs  
  • Pregnant or breastfeeding women
  • People with diabetes and other blood sugar problems
  • People with a history of eating disorders
  • People who take medications that require them to eat first

We need more research to fully understand how this diet can impact your mental health. One concern is that people who try IF could become overly fixated on food. You might also run the risk of passing on unhealthy ideas about eating to your children if they watch you focus on fasting. 

Intermittent fasting can be a very effective and beneficial dieting technique, but you have to make sure to use it as a tool and not let it control your life. Weight loss always involves difficulties, even setbacks, so you shouldn’t be too hard on yourself throughout the process. 

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What are additional benefits of IF? 

More research is needed for us to understand exactly how intermittent fasting can modify your body in the long run, but the initial results are all positive. 

Some studies have found that sticking to an IF diet can have many more benefits besides weight loss. Examples include: 

When should you talk to your doctor? 

You should talk to your doctor before starting IF to make sure that it’s safe for you. You should also see your doctor after you’ve started the diet if you experience persistent headaches, nausea, increased anxiety, or other concerning symptoms. 

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Medically Reviewed on 6/1/2022
References
SOURCES:

Alton Memorial Hospital: "Intermittent Fasting: Is It Better Than Typical Weight Loss Diets?"

Harvard School of Public Health: "Diet Review: Intermittent Fasting for Weight Loss."

Johns Hopkins Medicine: "Intermittent Fasting: What is it, and how does it work?"

Massachusetts General Hospital: "Doctor Recommends Intermittent Fasting."

Official Publication of the College of Family Physicians of Canada: "Intermittent fasting and weight loss."

Rush Memorial Hospital: "How To Maximize Weight Loss With Intermittent Fasting."