Alternate-Day Fasting: Everything You Need to Know

If you check any recent roundup of extremely popular diets, you will surely see intermittent fasting (IF) on the list. Isn’t it great to just be conscious about what you eat only for a couple of days a week? People cannot stop talking about the many health benefits of IF! Most use IF to lose weight, improve health, and simplify lifestyles. It can help you live longer, too (1, 2)! These benefits don’t sound too shabby, do they? 

However, similar to other weight loss programs, this approach, which calls for long stretches of time with limited to no food, is not an easy and quick fix. But as per health experts, it can really be effective if it is the right one for you. 

IF is not for everyone! It appears that whether or not IF will work for you comes down to human biology. While shorter periods of fasting are generally safe, some of the extended fasting times associated with IF aren’t recommended for certain groups of people. 

You may have considered trying it but worry that you won’t be able to stick to a fasting schedule every single day. According to one study, though, you can take days off of fasting and still reap all the benefits of fasting. This is also known as alternate-day fasting. 

Read on to get a closer look at what IF is in general, its health benefits, and how to do alternate-day fasting. 

What is Alternate Day Fasting and How Does It Work?

Intermittent fasting is not a diet. It is a timed approach to eating. Unlike other diet plans that restrict calorie intake, IF does not specify the type of foods you must eat or avoid. Rather, it is more focused on the time when you should consume them. It is best described as an eating pattern. 

All types of IF are promoted to change body composition by losing weight and fat mass, and to improve markers of health that are related to cholesterol and blood pressure (3). It can also offer physiological benefits over continuous diets for weight loss. It reduces body weight and appetite but not other adaptive responses (4). 

The concept of fasting isn’t new at all! In fact, it is often done for spiritual benefits as described in the early texts by Plato, Socrates, and other religious groups (5). 

There are actually several ways to do IF. All of them are effective, but which one fits best will depend on individual factors. 

Alternate-day fasting, as the name suggests, involves limiting food intake every other day. You can allow approximately 500 calories during the fasting periods. There have been several health benefits associated with this technique. However, a full fast every other day is quite extreme, hence not recommended for beginners. You’ll feel extremely hungry several times weekly, so it is quite hard to maintain. It takes time to get used to this fasting method. 

What Are the Possible Health Benefits of Alternate-Day Fasting?

Now that you have familiarized yourself with the many IF options you can do, it’s time to know the powerful benefits they have for your brain and body. Intermittent fasting, in general, can help you live a healthier and longer life by doing the following: 

1. Changing Cell Functions, Genes, and Hormones

 When you fast, your body initiates repair processes on a cellular level and modifies hormone levels to access stored body fat easily. The following changes can be observed: 

  • Blood insulin levels drop significantly to promote fat burning (6). 
  • Blood levels of growth hormone increased up to 5-fold to facilitate fat burning, muscle gain, and several other benefits (7, 8).
  • The body induces cellular repair processes like the removal of waste products from cells (9). 
  • There are also beneficial changes in genes and molecules related to longevity and protection against diseases (10).

2. Lowering Insulin Resistance and Risk of Type 2 Diabetes

Who doesn’t know type 2 DM? It has become incredibly common in the past few years! Its main feature is high blood glucose levels in the context of insulin resistance. Anything that decreases insulin resistance should help lower blood glucose levels and protect against type 2 DM. 

Good thing, IF has shown major benefits for insulin resistance, which led to an impressive reduction in blood glucose levels. Human studies showed that IF could help reduce fasting blood glucose by 3-6% and fasting insulin by as much as 20-31% (11). Evidence in rats also showed that IF could be protective against kidney damage, which is a common serious complication of DM (12).

3. Reducing Oxidative Stress and Inflammation

 We all hear about antioxidants every now and then! It appears to be one of the most talked-about topics in the health industry today, along with the many products being advertised for it. 

Oxidative stress, which is an imbalance between the production of reactive oxygen species or free radicals and antioxidant defenses, is known to cause aging and several chronic diseases (13).  It involves free radicals, which damages important molecules like DNA and protein (14). 

Did you know that apart from taking supplements, you can enhance your body’s resistance to oxidative stress and help fight inflammation by doing intermittent fasting? A growing number of studies can help support these claims (15, 16).

4. Improving Heart Health

 Heart diseases have always been one of the world’s biggest killers (17)! Many risk factors are associated with either an increased or decreased risk of heart disease. Animal studies on IF have shown to improve these risk factors, including blood pressure, cholesterol levels, blood triglycerides, blood glucose levels, and inflammatory markers (18, 19).

5. Preventing Cancer

Fasting initiates cellular “waste removal,” known as autophagy (20). Cells break down and metabolize broken and dysfunctional proteins that accumulate inside the cells. Evidence showed that increased autophagy might offer protection against cancer (21). 

Fasting also has beneficial effects on metabolism. Animal studies indicate that this can help cancer, too (22, 23)! What’s more, is that IF has also shown to reduce the side effects of chemotherapy on human cancer patients (24). 

6. Delaying Alzheimer’s Disease

Alzheimer’s is a common neurodegenerative disease. There is no cure available for this disease yet, so prevention is very critical. A study in rats shows that IF can help delay the onset of Alzheimer’s or reduce its severity (25). Also, in a series of case reports, daily short-term fasts were proven to help improve Alzheimer’s symptoms in 9 out of 10 patients (26). Other studies suggest that fasting may also offer protection against other neurodegenerative diseases like Parkinson’s disease and Huntington’s disease (27). 

7. Promoting Brain Health

IF is known to improve several metabolic features, which are important for brain health, this includes less oxidative stress, less inflammation, and low blood glucose levels and insulin resistance. Many studies in rats have proven that IF can help increase the growth of new nerve cells for better brain function (28). 

It can also increase the levels of a hormone known as the brain-derived neurotrophic factor (BDNF) (29, 30). A deficiency of this hormone has been implicated in several other brain problems and depression (31). Other evidence revealed that IF could help protect the brain from the damage caused by strokes (32). 

8. Prolonging Life Span 

One of the most exciting benefits of IF is its ability to extend your lifespan! Rat study has shown that IF can extend lifespan in the same way as continuous calorie restriction (33). In some of these studies, the effects were dramatic. Rats that fasted every other day lived 83% longer as compared to those who did not fast (34). 

Although this is far from being proven in humans, IF has become very popular among the anti-aging crowd. 

More Research on Alternate Day Fasting

A lot of the research on this has focused specifically on alternate-day fasting. Research shows that it is just as effective as very-low calorie diets for weight loss, but it may be easier (35). Some patients found it simpler to fast every day than to restrict calories every day.

Unfortunately, an alternate-day fasting scheme doesn’t prevent your metabolism from fighting back against weight loss. This review looked specifically at metabolic adaptations to weight loss. You might expect that alternate-day fasting would be superior to constant dieting here, but the study didn’t actually find evidence of that – both were about the same.

As for non-weight-related benefits, the evidence in humans is mixed but encouraging.

A 2007 review of alternate-day fasting found that it may help to improve blood lipids, but also found that alternate-day fasting and ordinary calorie restriction were equally good for insulin levels and blood sugar control (36).

Another study found that severe calorie restriction, less than 20% of energy needs, on alternate days reduced inflammation and oxidative stress in overweight adults with asthma (37).

Intermittent energy restriction, less than 25% of energy needs, can also help reduce inflammation and improved blood lipids in overweight women.

Is it a magical cancer prevention or cure strategy? No, but nothing really is. In overweight subjects, one-day fasts seem to reduce some measures of overall physical stress and chronic poor health.

How to Do Alternate Day Fasting? 

Fasting 1-3 Days Per Week

This technique makes your social calendar easier. However, one big barrier to alternate-day fasting is that most of us have a weekly schedule, and weeks have an odd number of days. Fasting every other day means that you’re constantly changing the day of the week when your fast happens, which can be inconvenient. It may be easier for some people to fast on specific calendar days, rather than every other day.

Modified Alternate-Day Fasting

This reduces hunger and makes the fast more tolerable. In a modified alternate-day fast, you basically get one mini-meal to tide you over on “fast” days. So it’s not really fast; it’s more of an alternate-day crash diet. In fact, some of the studies in the section about non-weight-loss benefits used this approach rather than absolutely 0 food intake on fast days. 

One study found that the “automatic calorie restriction” benefits still held true with a modified one-day fast (38). On their “fast” day, the subjects got 25% of their calorie requirements. On the next day, they ate a little more, but not enough to make up for the huge deficit that they created on the fast day.

Another research says that just one modified fast day per week, 330-430 calories on the “fast” day, made weight maintenance easier (39). In fact, it outperformed a typical “heart-healthy” Food Pyramid-style diet.

If you took this approach with a Paleo-style diet, your mini-meal on the “fast” day might be:

  • 3 eggs fried in butter with some vegetables
  • A small piece of salmon with wilted spinach
  • Roasted vegetables with 1/2 chicken breast

Are There Any Risks Involved? 

Fasting or ADF isn’t for everyone. For one, there may be differences in how men and women respond to fasting. While IF can help lower insulin resistance, you should be wary of doing ADF if you have diabetes because you should be eating regularly. This has to be consulted with your doctor first and a healthy diet schedule should be planned accordingly with your dietician. 

The diet you choose should be one that you will enjoy the most. If you enjoy a low-fat diet, then this is your answer. If you like higher fat-foods, lower your carbs and you will feel content and be healthy with these choices. You will stick to the plan you have chosen because you like the food. It is a “winning” decision.

More Tips When Trying Alternate-Day Fasting 

  • Always check with your doctor first. Again, this eating regimen may not be right for people with type 2 diabetes or cardiovascular disease without the approval of a medical professional. 
  • Try skipping breakfast and lunch, but keeping dinner at first to ease into the regimen, and then expanding to a full 24-hour fast.
  • Some people prefer a modified version of alternate day fasting where they stick to 500 calories one day, then still eat anything they want the next. In this version, go for at least 50 grams of protein on fasting days to help keep hunger at bay. A good option may be a salad with beans or some chicken.
  • Don’t drink any sweetened beverages on fasting days, even if they contain artificial sweetener, because the sweet taste can cause hunger. Water is best, though black coffee or tea also works. But don’t overdo it: being hungry and caffeinated can be a terrible combination. Hot beverages can help curb hunger.
  • Experts do not recommend exercising during the first week people try the plan, but it is fine after some weeks. In fact, you are even more energetic when you exercise on a fasting day versus the non-fasting day. However, if you’re fasting and burning calories during a workout, you could feel weak.
  • Be aware that on the days when you’re not eating anything, it may be harder to focus at work or to stay in a positive mood. Keep busy, focus on tasks at hand and do things that keep you away from the kitchen and snacks.
  • On non-fasting days, focus on eating a healthy diet with lean protein and lots of plant-based foods and whole grains.

Key Takeaway 

Fasting is actually a natural part of the human life cycle. Many have fasted unknowingly throughout their lifetimes by skipping breakfast or eating an early dinner. While more structured methods may work well for most people, some may not benefit from them at all. 

While an average person will likely experience no or minimal side effects, people with certain medical conditions or who are taking medications should consult a doctor first before trying alternate-day fasting or any other IF technique. 

Remember, you do not have to exclude certain foods from your diet; you should just aim to eat a balance of protein, fiber, and vegetables. Drink plenty of fluids too! 

If intermittent fasting makes you feel great, and you find it easy to maintain, it can be a powerful tool to lose weight and improve your overall health. 









































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