Alternate Day Fasting – What is It?

Guide to alternate-day fasting for beginners

Fasting on alternate days Health advantages
Metabolic wellness
Is it secure?
Four helpful hints
Three main conclusions

With alternate-day fasting, you alternate between days when you eat normally and days when you consume very few or no calories. Study more
Easy to accomplish: Calories are equally reduced over time without making one feel deprived, as opposed to restricting calories day after day, which can be difficult to maintain. Find out if it works here: Studies show Alternate-day fasting can cause a temporary, moderate loss of weight. Improved metabolic health is possible. Here’s why there has been a significant increase in interest in intermittent fasting, or purposefully going without food and calorie-containing beverages for a short period of time, in recent years. Alternate-day fasting is one of many types of intermittent fasting regimens that are available.

This article will give a general overview of alternate-day fasting and examine what the scientific literature has to say about how it affects blood markers for cardiovascular health, metabolic health, and weight loss. Additionally, it will discuss the security of alternate-day fasting and offer some helpful advice for successfully breaking a fast.

What is fasting on alternate days?

Contrary to what the name might imply, alternate-day fasting involves alternating between days of calorie restriction and days of unlimited eating.

You can either fast strictly, which involves consuming no calories at all, or you can fast moderately, which allows you to consume only 25% of your daily energy requirements, or roughly 500 calories. The modified method, which is the kind I’ll discuss in this guide, is the one that’s used in the majority of alternate-day fasting studies.

Food can be consumed all at once or in small meals spread throughout the day when fasting. As long as a meal has less than 500 calories, it can have either a high or low fat content. Either prepare your food from scratch or purchase packaged meals with predetermined calorie counts. In the majority of trials, water, black coffee, unsweetened tea, and sugar-free gum are also permitted.

Foods high in protein and fiber will help you feel less hungry while on a modified fast, and soups can make you feel full without adding many calories.

Here are some illustrations of balanced meals for fasting days that are under 500 calories each:
3 cups of vegetable soup and 3 to 6 hard-boiled eggs
A tablespoon of nut butter, up to a cup of berries, and one to two cups of Greek yogurt
4 to 6 ounces (115 to 170 grams) of grilled fish, chicken, or steak on top of a salad
There aren’t any strict guidelines for what to eat on a feast day — alternate-day fasting is about when to eat, not what or how much — but it’s always crucial to pick nutritious foods that are of high quality for overall health.

Benefits of alternate-day fasting for health

The majority of studies on alternate-day fasting in people have concentrated on how it can aid in weight loss, lower risk of metabolic diseases, and influence cardiovascular indicators. Let’s examine each in more depth.

Loss of weight

Our bodies must expend more energy than they consume in order to lose weight. Reducing the amount of food consumed at most meals is frequently the first step people take when trying to lose weight. Caloric restriction is what is meant by this.

People struggle to maintain calorie restriction because it calls for daily energy intake reductions, which can increase cravings and hunger. In a world where delicious, high-calorie foods are constantly available, it is simple to understand why people who attempt to diet by eating less every day, every day, frequently fail.

How to generate a calorie deficit in a way that is more comfortable and long-term sustainable is the part of the weight loss discussion that is frequently overlooked. Fasting on alternate days can accomplish this. The theory is that by eating considerably less every other day, a sufficient calorie deficit will be produced over time to result in weight loss. Even better, you won’t have to consume foods you dislike, spend a lot of money on supplements, or weigh, track, and measure every meal.

According to studies, alternate-day fasting and a high-carb diet result in moderate weight loss in a short period of time, with body weight dropping by 4% to 8% in just 6 to 12 weeks.

Even more weight loss may result from combining alternate-day fasting with a low-carbohydrate diet. The rate of weight loss resembles traditional caloric restriction quite a bit. It’s important because even a 5% weight loss can significantly enhance health outcomes.

Additionally, research participants who were alternate-day fasting lost up to twice as much weight when they added endurance exercise to their regimen as opposed to alternate-day fasting or exercise alone.

Sometimes, losing weight is the simple part; the harder part is often keeping the weight off permanently. Researchers have examined the amount of weight gain that occurs when alternate-day fasting participants stop receiving dietary guidance.

They discovered that participants experienced a mild weight regain of 1% to 2%, which is comparable to what is seen with traditional caloric restriction, when people were permitted a higher calorie intake on fasting days or fewer fasting days per week. The authors of the study suggested that in order to maintain weight loss, individuals may need to follow a stricter alternate-day fasting regimen.

Another crucial aspect to take into account when losing weight is body composition. Not muscle or lean tissue, but body fat is what you should aim to reduce. You burn more energy even when you’re at rest thanks to lean tissue, which helps maintain your resting metabolic rate.

According to research, people who alternate-day fast lose the majority of their weight as fat and only a small amount as lean muscle. Additionally, the belly region is where the dangerous internal fat that surrounds our organs is most frequently stored. The same might not hold true for healthy, lean people, as one study found that they lost more lean tissue than fat.

Alternate-day fasting may have a negligible or marginally beneficial impact on hemoglobin A1c (HbA1c) and fasting glucose levels, according to studies on metabolic health. HOMA-IR, a measurement of insulin resistance, and fasting insulin are both reported to be decreased by alternate-day fasting, particularly in those with the highest levels of insulin resistance.

According to research, people who are most at risk for developing diabetes benefit from alternate-day fasting more than caloric restriction when it comes to improving metabolic disease markers. The metabolic disease markers were not significantly different between subjects undergoing alternate-day fasting and caloric restriction in metabolically healthy adults with obesity.

According to the literature, those with more severe metabolic dysfunction may experience a more pronounced effect of alternate-day fasting on their metabolic health.

Studies on cardiovascular markers show that alternate-day fasting lowers triglycerides, systolic and diastolic blood pressure, total cholesterol, and low-density lipoprotein cholesterol (LDL-C).

Positive effects on LDL-C particle size have also been noted by researchers. After 12 weeks of intervention, LDL particle size was larger in subjects who exercised and followed an alternate-day fasting diet than in subjects who followed the diet alone. This is significant because larger LDL particles, as opposed to smaller ones, are linked to a lower risk of coronary heart disease.

Is it safe to fast on alternate days?

Fasting and starvation are often confused, but they are two very different things. Starvation is a regrettable situation brought on by factors beyond your control, such as war or famine, whereas fasting is something you choose to do with a specific goal in mind.

Alternate-day fasting seems to be safe in the short and long term, provided you are not underweight or malnourished. The most frequent side effects include weakness, dizziness, bad breath, constipation, irritability, and hunger. Mild symptoms are frequently reported and disappear a few weeks after starting alternate-day fasting.

Although these are not always the results, some studies on caloric restriction suggest that it may impair immune response in animals and reduce bone mineral density in people. When compared to individuals who had never fasted, there was no difference in bone mass, bone mineral density, white cell counts, or other indicators of immune function in those who had been alternate-day fasting on their own for more than six months.

Furthermore, there was no evidence that long-term alternate-day fasting had a negative impact on thyroid function, despite some anecdotal reports suggesting this might be a problem with frequent, extended fasting, particularly for women.

However, some people should probably avoid trying to fast.

  • This includes women who are expecting or nursing.
  • Children and infants taking insulin or other diabetes medications without a doctor’s supervision
    elderly people, underweight individuals, and those with a history of eating disorders like anorexia
  • If you decide to begin alternate-day fasting, it’s a good idea to seek medical supervision as with any dietary change.

4 helpful suggestions for fasting

To successfully incorporate alternate-day fasting into your health routine, try these useful tips.

Plan ahead
When life gets complicated, knowing what and when you’re going to eat will keep you on track. Having your meals prepared in advance reduces the likelihood that you’ll stop at a fast food restaurant on your way home from a busy day, which is especially important for a fasting day. Planning to fail is a cliche that applies here.
Don’t be afraid of salt, and add electrolytes as well.
Regardless of the protocol you choose, fasting can deplete your body’s stores of sodium, magnesium, potassium, and calcium. If you exercise regularly or consume a diet low in processed foods and carbohydrates, you lose electrolytes even more quickly. You can prevent a nutrient deficiency by liberally salting your food and taking electrolyte drops, powders, or pills as a supplement. Alternately, try the electrolyte elixir from Diet Doctor, which can be consumed on eating or fasting days.

Become Fat Adapted
When your metabolism is flexible, your body can use its fat reserves as energy, allowing you to avoid hunger for longer periods of time. Although fasting itself enhances fat adaptation, a low-carb, ketogenic diet is a great way to get your body ready for fasting.

Keep active
When you are actively engaged in something to keep your mind and body busy, fasting is easier. When you are both bored and hungry, it is tempting to break your fast. This would be a great time to go for a long walk, work on a difficult puzzle, or engage in whatever activity keeps you busy both mentally and physically.


Alternate-day fasting is an alternative to traditional caloric restriction that has the potential to aid in weight loss, metabolic health improvement, and a positive impact on blood markers related to your cardiovascular system. Since you only need to cut back on your energy intake every other day, it may be simpler to implement than the customary advice to do so.

Alternate-day fasting is generally safe, with the exception of a few minor side effects. If you’ve had trouble with other diets in the past, it’s definitely worth a shot.