Alternate Day Fasting: What Is It and How Does It Work?

Alternate Day Fasting: What Is It and How Does It Work?

With many celebrity adherents, like Terry Crews, Hugh Jackman, and Jennifer Lopez, alternate day fasting, also known as intermittent fasting, has become something of a trend. Professional athletes, bodybuilders, and those who want to lose weight and gain lean muscle mass have been following this kind of program or diet for years.

For those who have just stumbled on the concept, you no doubt have a number of questions. How does it work? Is it actually effective? We'll answer both of those questions and more here.

What Exactly Is Alternate Day Fasting (ADF)? 

The name of the diet says it all: when you're following it, you restrict calorie intake one day and then eat whatever you want the next. This daily calorie restriction pattern repeats itself every single day so that participants spend every other day not eating with plenty of food included in the diet in between.

There are two main ways to "fast" on your fasting days. Some people restrict food entirely, only drinking liquids free of calories, like water, unsweetened tea, and black coffee. However, others limit themselves to a mere 500 calories on the fasting days, allowing themselves to eat a very small amount of specific, healthy foods like lean protein and whole grains.

On alternate days, when you aren't fasting at all, your diet is unrestricted. You can eat whatever you want. Whether you decide you want the cheese fries to go with your burger or a milkshake as dessert, you can have them. Those are your "cheat days."

Why Do People Follow This Diet?

On top of the celebrities who say that the alternate day fasting diet has provided them with health benefits, there are several upsides. If you're worried about being able to restrict your calories day after day or think that following a macro cycle is something that you just can't commit to, then fasting every other day seems like a good trade-off. After all, you don't have to worry about counting calories every other day of the week.

In addition to not feeling as though you're deprived of foods that you love, people have indeed lost body weight while on this diet. As long as you don't go wild during your cheat days (also known as feasting days), you'll see some progress, especially if you pair your alternate day fasts with a fitness program.

There’s also some evidence on the following:

  • ADF may decrease some of the risk factors that can contribute to type 2 diabetes by combating insulin resistance.
  • ADF may help adults with obesity lose weight.
  • Fasting may help regulate blood glucose.
  • This eating plan may help lower LDL cholesterol and triglycerides.

Some Data on Alternate Day Fasting

Thankfully, a number of studies and clinical trials have been done on alternate day fasting. The results show that over the course of six months on the diet, weight loss can be achieved. In one particular study, people were broken up into three groups.

The fasting group spent their days alternating between eating around 25% of the food they needed based on their ages and weights and 125% of the calories that they should have. The second group followed a diet that consisted of eating only 75% of the calories that they should be eating every day, restricting their foods in general, without fasting. Finally, the last group (the control group) proceeded with regular food intake.

By the end of the study, people in both the fasting group and the general calorie restriction group lost weight. The average loss was about 12 pounds. Plus, their overall health increased as their blood sugar levels stabilized and their blood pressure went down, among other things. This shows that intermittent fasting regimens are, on a short-term basis, comparable to regular dieting.

Of Course, Nothing Is Perfect 

While the study points out that people who followed an alternate day fasting diet lost weight over six months, many gained back some of the weight over the next six months. In addition, the LDL proteins in the blood, which place people at risk of heart disease, went up, meaning that fasting every other day didn't help their heart health as much as it did for the initial six months.

According to the experts, an alternate day fast is good in the short term but not so good in the long term. You may see some weight loss or changes in body composition right away, but if you try to keep that weight off without a good diet and exercise plan in place, you'll gain some of it back in the long term.

Plus, it can be tough to sustain a diet where you eat a lot one day and nothing the next. In fact, the study had a fairly high dropout rate because it’s a hard habit to maintain.

Other Downsides to the Diet 

In addition to people gaining some weight back and seeing their bad cholesterol go up during their final six months on the diet, there are other downsides to alternate day fasting.

What About Exercise?

If you plan to include physical activity in your routine, should you do so on your fasting days? This isn't recommended, as you need carbohydrates, proteins, and fats to power your body. Trying to run a mile on an empty stomach isn't a good idea.

If you want to exercise, you'll need to do so on your cheat or eating days. This limits the number of times that you can work out each week.

Hunger Can Make It Tough To Concentrate

People with jobs that require a lot of concentration may find that they have a hard time working on their fasting days. A lack of food can lead to a lower amount of brainpower. Plus, hunger can make a person cranky and short-tempered, neither of which is good if you need to be up front leading a board meeting or making a presentation.

How Strong Is Your Willpower?

In order to maintain a diet where you eat everything one day and nothing the next, you need to have a lot of willpower. Are you able to fend off the hunger pangs and avoid reaching for a quick snack on your fasting days?

Even if you choose to go the 500-calorie cheat-day route, you may end up lacking the mental strength to simply stay on your diet. After all, the body wants food, and it will find a way to make you get it.

So, Should You Fast Every Other Day? 

There isn't a straightforward answer to that question. If you think that you have the willpower to eat a lot one day (within reason) and nothing or a very small amount the next, then it's worth a try. If you can combine that diet with exercise, at least on your cheat days, then you'll lose weight over the short term.

However, according to the studies, when you follow the alternate day fasting diet for a longer period of time, you may find yourself gaining back some of the weight, and you may end up exacerbating your health issues.

Instead, if you want something that will work over the long term, consider one of these alternative options.

Intermittent Daily Fasting 

People have had some success fasting for several hours over the course of a day and then eating normal meals during the other hours. For example, they would fast from 8 am to 8 pm and then eat dinner at 8 pm. This is just as tough mentally as fasting for an entire day, although it gives you something to look forward to once your fasting time comes to an end.

In addition, since there are standard meals once the fasting ends, instead of a food free for all, you are still following a slightly restricted diet, making it easier to lose that weight. Followers of this diet have even managed to work out while in the fasting period, with plenty of success.

Regular Calorie Restriction

There's nothing wrong with a standard calorie-restricted diet. Whether you want to cut back on certain food groups or simply just eat less and exercise, you'll have some success. The weight will come off, and this type of diet is much easier to stay on, as you can eat foods that will leave you feeling fuller longer, instead of being so hungry that you can't stand it during a fasting period.

It's Up to You 

In the end, which diet you choose to follow is entirely up to you based on how your body feels. Alternate day fasting does work, as long as you can stay on a fairly restricted diet during your cheat days and not go completely wild.

Although the study showed otherwise, some people have managed to stay on the diet and still lose weight over the long term. If you can handle the fasting days (which get easier over time), you'll be able to follow an alternate day fasting schedule, and you may be successful with your weight loss or weight maintenance plan.

Sources:

Eat Only Every Other Day and Lose Weight? | Harvard Medical School Health Publishing

Alternate Day Fasting: A Comprehensive Beginner's Guide | Healthline

Fast and Feast Diet Works for Weight Loss | WebMD

Alternate-day fasting alleviates diabetes-induced glycolipid metabolism disorders: roles of FGF21 and bile acids | NCBI

Alternate-day fasting and chronic disease prevention: a review of human and animal trials | American Journal of Clinical Nutrition 

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