Alternate Day Fasting vs Intermittent Fasting: The 5 Differences

Fasting comes in different types of approaches and it may seem like a disconcerting idea if you are used to eating three meals a day plus a snack—or if you need to lose a few pounds through it.

Two of its known approaches are alternate day fasting and intermittent fasting and is not as extreme as it appears. Both have demonstrated to have a number of health benefits other than weight loss—though it can undoubtedly help with that as well.

This article will contain further information about alternate day fasting vs intermittent fasting, and show which is best suited to you. Continue reading below and see a comprehensive look at these two approaches.

Intermittent Fasting

Intermittent fasting is a type of eating habit that consists of regular, short-term fasts — or periods of little or no food consumption.

For hundreds of years, people have practiced intermittent fasting in various ways for religious and health reasons. Presently, most people think about intermittent fasting as a way to lose weight. Short-term fasting causes people to consume fewer calories, which may result in weight loss over time¹.

It is recommended for changing body composition by losing fat mass and weight, as well as improving disease-related health markers such as blood pressure and cholesterol levels².

Intermittent fasting may help change risk factors for health disorders such as diabetes and cardiovascular disease by decreasing cholesterol and blood sugar levels¹. In terms of weight loss efficiency, studies do not consistently suggest that intermittent fasting is superior to continuous low-calorie diets³.

Different Eating Plans

There are various approaches to intermittent fasting. Among the most well-known are:

Alternate-Day Fasting (ADF)
- Alternate-day fasting is an intermittent fasting strategy with a simple structure. You fast every other day on this regimen but can eat whatever you want on the non-fasting days. Alternating between days with no dietary restriction and days with one meal that supplies around 25% of daily calorie needs. For example, fasting is observed on Mondays, Wednesdays, and Fridays, with no food restrictions on the other days³.
- Some variations of this diet advocate a “modified” fasting technique that entails ingesting 500 calories on fasting days. Other variants, on the other hand, completely exclude calories on fasting days. If you’re new to intermittent fasting, start with a modified fasting strategy. Whether you begin with a reduced fasting plan or a full fast, it is recommended to keep a balanced diet that includes high-protein foods and low-calorie vegetables to help you feel full¹.
Whole Day Fasting
- This involves 1-2 days a week of complete fasting, or up to 25% of your daily calorie needs, with no food restrictions on the remaining days³.
- A known whole day fasting is the 5:2 Diet. The 5:2 diet is a simple intermittent fasting regimen. You eat regularly and do not restrict calories five days per week. Then, on the remaining two days of the week, you cut your calorie consumption to one-quarter of your daily requirements. If you are someone who consumes 2,000 calories per day on a daily basis, this would imply cutting your calorie consumption to 500 calories per day, two days per week¹.
Time-Restricted Feeding
- This type of fast follows a daily meal plan with a fasting time frame³.
- A popular time restricted feeding is the 16/8 Method. A 16/8 intermittent fasting strategy is one of the most common types of fasting for weight loss. The strategy limits eating and calorie-containing beverages to an 8-hour window per day. It entails fasting for the remaining 16 hours of the day. While other diets can have tight restrictions and regulations, the 16/8 technique is based on a time-restricted feeding (TRF) concept and is more flexible. You can consume calories during any 8-hour period you want. Some people skip breakfast and eat from midday to 8 p.m., while others avoid eating late and stick to a 9 a.m. to 5 p.m. schedule¹.

Alternate Day Fasting (ADF)

ADF regimens are characterized as alternating ‘feast days’ in which food is consumed ad libitum with ‘fast days’ in which food is withheld or limited¹. Alternate-day fasting may be simpler for you to keep to than other forms of diets.

A yearlong trial, on the other hand, discovered that adherence to alternate day fasting (in which calorie intake was cut to 25% of energy demands on fasting days) was not superior than daily calorie restriction.

The modified variant, with 500 calories on fasting days, was employed in the majority of the investigations on alternate-day fasting. This is considered much more maintainable than conducting full fasts on fasting days, yet it is just as effective⁴.

Let’s tackle the effects of alternate day fasting on the following factors below:

Weight Loss
- ADF and daily calorie restriction have both been found in studies to be similarly efficient at reducing dangerous belly fat and inflammatory markers in obese people. Although ADF may be beneficial for fat loss, recent research indicates that it is no more successful than typical calorie restriction in terms of weight loss or muscle mass preservation^5,6. Furthermore, weight reduction under ADF, like other methods of calorie restriction, may be enhanced when combined with increased physical activity.
Hunger
- The effects of ADF on hunger are erratic. After 24 weeks of follow-up, one study comparing ADF to calorie restriction discovered that ADF boosted levels of brain-derived neurotrophic factor (BDNF). Researchers concluded that ADF may cause long-term alterations in BDNF, which may support better weight loss maintenance. Human studies have not revealed any substantial effects of ADF on hunger hormones. However, animal studies have indicated that, when compared to other diets, modified ADF resulted in lower levels of hunger hormones and higher levels of satiety hormones^7,8,9. Another thing to consider is compensatory hunger, which is a common adverse effect of standard daily calorie reduction^10,11,12. Compensatory hunger refers to increased hunger in reaction to calorie restriction, which drives people to overeat when they eventually allow themselves to eat.
BodyComposition
- ADF has been proven to have distinct effects on body composition, both during dieting and weight maintenance. Traditional calorie-restricted diets and ADF are both equally effective at reducing weight and fat mass, according to studies. According to some research, ADF may be more useful for muscle preservation than other methods of calorie restriction. A recent, high-quality study, however, suggests that ADF is no more efficient than typical calorie restriction in retaining muscle mass⁴.

Alternate Day Fasting vs Intermittent Fasting

Intermittent fasting, alternate-day fasting (ADF), and other kinds of periodic caloric restriction are not true strategies of energy deprivation because people can consume twice as much on the second day, at least theoretically¹.

Intermittent fasting is any eating strategy that limits when and how much you consume. There are numerous variants, each promising a variety of health benefits ranging from weight loss to a lower risk of several ailments.

Alternate day fasting is a popular type of intermittent fasting. Basically, It’s just an prolonged version of it. This strategy tends to shed more weight than others, but it might be difficult to stick with. Fasting every other day and eating whatever you want on non-fast days is what alternate-day fasting entails¹³.

The Differences Of Alternate Day Fasting And Intermittent Fasting

Both alternate day fasting and intermittent fasting can help you lose fat and keep it off, these are some of their key differences:

Intermittent fasting is easier to sustain – you can do alternate day fasting only for days at a time but with intermittent fasting, it can be done everyday.
More autophagy with Alternate Day Fasting – with ADF, there are more chances of autophagy, which is your body’s process of cleaning out damaged cells to regenerate newer and healthier cells. Though more autophagy isn’t always better and IF can already keep your basal level of autophagy more elevated than regular eating.
Can eat more carbs and stay in ketosis with ADF – you will be able to produce more ketones and experience lower glucose with ADF than with IF because you have fasted beyond 24 hours. Ketones are chemicals produced by your body when it burns fat for energy rather than sugar.
Be able to maintain and build more muscle with IF – to stimulate muscle protein synthesis and build muscle, It’s crucial to consume protein. Though if you are overweight, you can still be able to burn fat and build muscle with ADF. The leaner you become however, the more difficult it is to maintain.
IF is less stressful on your body – intermittent fasting won’t be as strenuous after doing it for even just a few days but with ADF, your body may continuously go through stress hormones.

What To Eat During Fasting Days?

Before you incorporate any changes to your diet in any significant way, be sure to consult with a health professional to make sure it’s the best decision for you. That said, with fasting, there are two parts to it: the eating window and the fasting window.

The general rule during a fast is you refrain from eating or drinking any calories. Also, while intermittent fasting has no defined food, it is recommended to consume low carb in times of eating. Here are some of the best foods to consume:

Protein
- Getting enough protein is important as it helps preserve your muscles as they shed fat, and it also works to keep your immune system in great shape. It has a moderate impact on your insulin and a slow blood sugar response.
Amino Acids
- All amino acid supplements contain calories, but because they aren’t whole protein, supplement firms aren’t supposed to list them on supplement facts panels. They actually have the same number of calories per gram as protein, which is four. Though they technically break a fast, the impact on weight reduction is minimal.
Coffee
- Calories can also be found in coffee, MCT oil, and ketones. Black coffee contains only 10 calories, making it an insignificant impact during a fast (coffee actually tends to improve long term health).
MCTs
- MCTs break your fast but not enough that it will negate the benefits of fasting. MCTs can be absorbed quickly in your body because they’re water soluble and have short carbon chains. This allows them to bypass your digestive system and reach your liver, where they are quickly converted into ketones (fuel).
Diet Drinks
- Diet drinks are also generally safe. Some artificial sweeteners may cause a modest insulin or glucose increase. Sucralose, saccharin, and aspartame are three of them. Some sugar alcohols, like maltitol and sorbitol, have the same effect.

Keto Diet

You will most likely enter ketosis simply by fasting, so you do not need to follow a ketogenic diet on feeding days/windows. A keto diet’s aim is to cut back most of the carbs because it gets more calories from protein and fat and less from carbohydrates.

When you eat less than 50 grams of carbs a day, your body eventually runs out of fuel (blood sugar). If your primary goals are weight loss and maintaining your fasting diet, keto-adaptation might make fasting times appear simpler because your body is already willing and able to use fat (body fat) as fuel.

Consuming proteins and fats instead of carbohydrates improves your satiety without you even recognizing it, which is known as autoregulation. You eat less if you become full faster¹⁴.

Conclusion

One of the most significant challenges with weight reduction regimens is compliance; most people give up too soon or cheat too frequently to be successful. It is easier to achieve success with set parameters and easy fasting restrictions.

Furthermore, though prolonged fasting periods may have some long-term health and lifespan benefits, it is not without its risks such as headaches and fatigue.

Both alternate fasting and intermittent fasting are effective weight loss methods, and while prolonged (alternate) have the added benefit of autophagy, its intensive calorie restriction makes intermittent fasting an easier option for long term weight loss.

If you’ve been thinking about giving intermittent fasting a chance, it’s generally better to start with simpler approaches of intermittent fasting and then work your way to prolonged versions of it such as the alternate day fasting method.