Intermittent Fasting

Intermittent fasting has become a popular diet trend in the past few years. Gone are the days when gurus would recommend 6 small meals, two to three hours apart. Nowadays, the pendulum has swung to a new style of eating. This new style of eating is termed intermittent fasting.

Claims of Intermittent Fasting

This new style of eating has become an immensely popular movement, and it’s hit mainstream markets too. Proponents claim that intermittent fasting helps you burn more fat, build more muscle, reduce hunger and cravings, include more satiating meals and stay leaner.

Some health experts claim intermittent fasting might have health benefits for you across your lifespan and in the face of chronic or acute illness. Still, detractors of intermittent fasting say this type of eating might cause more muscle loss, hunger, or other side effects.

Is Intermittent Fasting Just a Fad?

Additionally, other experts are worried intermittent fasting’s benefits are overstated, that fasting has reached fad status, and that mass marketing has oversold this style of eating. So, what’s the scoop on intermittent fasting? Is it a useful dietary tool or is it pure magic? Or, is it more trouble than its worth?

Let’s find out.

Intermittent Fasting and Weight Loss

Whether you are trying intermittent fasting for weight loss, weight gain, or simply to maintain your weight, it’s important to understand that the laws of thermodynamics still apply. Energy cannot be created or destroyed. So, if you eat more calories than your body burns, you will end up storing some of that energy as fat. If you eat fewer calories than you burn, you will end up losing some body fat. So intermittent fasting is not some magical strategy where you can cram 30,000 calories into two meals between 10 am and 2 pm and expect to lose weight.

You will still have to adhere to a good calorie target for your goals. Calorie intake is still king. For some people, intermittent fasting can help with weight loss because you are restricting yourself from eating certain periods of the day. This can cause reductions in your calorie intake and result in weight loss.

Intermittent Fasting Health Benefits

However, intermittent fasting has also been linked to some health benefits, which I will discuss below.

It is difficult to tease out how much those benefits are due to the periodic fasting itself, or just due to weight loss. As you will see later, intermittent fasting might provide some benefits for brain health, cancer survival, heart health, working memory and more. However, these benefits are also observed with ongoing calorie restriction in healthy people. It is difficult for researchers to understand how much the health effects are due to fasting and how much they are due to caloric restriction.

Before I get into more on the potential health effects of intermittent fasting, I want to discuss how you would actually practice this style of eating. I also want to discuss how intermittent fasting differs from typical eating schedules. I will also show you how you can fit this eating style into your lifestyle.

Intermittent Fasting Schedule

Intermittent fasting plans propose fasting for the majority of the day and then putting all your calorie and nutrient intake into a specific time window. While you can still drink water and other non-caloric beverages, you cannot eat any food during this fasting window.

Normal Feeding Schedule

Contrast this style of eating to the typical day in the life for most people. Most people eat during their entire waking life, consuming three full meals and one or two snacks throughout the day. And provided you are eating healthfully, this can be a healthy pattern, even ideal for some people. While some people feel that this style of eating might be a marketing ploy popular since the industrial era, there are well-documented benefits to this eating style.

Health Benefits of Regular Feedings

For one, eating at regular intervals can help to prevent spikes and crashes in blood sugar that can cause mood swings, excessive hunger, cravings or focus problems. Eating at regular intervals can also help you to ingest enough calories and nutrients throughout the day. There is also some research that spreading protein out into regular meal intervals can help increase whole body protein balance, muscle protein synthesis and muscle growth.

Additionally, there is a threshold of protein you need to consume in each given meal to maximize muscle synthesis and new muscle growth. And finally, eating balanced meals throughout the day can have important implications for your workouts and training results.

Steady meals throughout the day, including a pre-training snack including a balanced intake of macronutrients can help prevent mind and muscle fatigue during intense workouts.

Regular Eating Pattern and Hunger Signals

Anecdotally, a daily meal frequency of three to five meals per day can also promote another healthy eating pattern. Regular feedings can help you learn to eat when hungry and stop when full.

Between meals, blood sugar levels start to drop within three to five hours, helping to orchestrate signaling mechanisms in your body that you are hungry and it is time to eat. When you have consumed enough calories and nutrients, your body signals to your brain that it is time to stop eating. So even though the American way of three meals and two snacks might be aggressively marketed, it might also have some legitimate benefits for human health, performance and productivity.

The Rules of Intermittent Fasting

Under an intermittent fasting protocol, you will eat all your meals and snacks within a certain time window. You cannot eat outside of the feeding window. Additionally, you cannot drink caloric beverages during that window. Depending on the type of protocol you are using, you might fast for 16 hours, 20 hours, or have alternate days of fasting and eating.

Can I drink During Intermittent Fasting?

During your fasting window, you may certainly drink fluids, but you want to avoid consuming any calories during your fast. Here are some sample beverages you can consume during fasting windows.

Water
Lemon Water
Powerade Zero
Gatorade Zero
Coffee
Tea
Diet Soda
Diet Tea/Lemonade

However, you cannot drink these items during your fasting windows.

Regular Soda
Coffee with cream and sugar
Juices
Lemonade
Alcoholic Beverages
Health Drinks
Smoothies
Protein Shakes

Types of Intermittent Fasting

There are many ways you can do intermittent fasting. This is not a comprehensive list, but it will give you some ideas on how to set up your own fast.

16/8 Fast

This is the most popular and beginner friendly form of fasting. You fast for 16 hours, and then eat all your meals within an 8 hour window. The fasting window can include the time you sleep. Perhaps you sleep for 8 hours per night. If you stop eating for four hours before bed and delay your first meal for four hours after waking, you can easily start this type of fasting.

20/4 Fast

With this schedule, you fast for 20 hours and then schedule your meals within a four hour window. This approach is a bit more extreme. You may only be able to fit one large meal into your feeding window. Still, this approach might be desirable for those with difficult work or life schedules.

22/2 Fast

Eat all your calories in 2 hours and fast for the other 22. This is a quite extreme form of fasting that might not be practical for most people.

Alternate Day Fasting

With alternate day fasting, you may not eat for an entire day, but then resume your normal eating schedule on the next day. You might repeat this cycle, fasting one or two days per week on non-consecutive days. You might intentionally compensate with higher calories on your non-fasting days.

Alternate Day Dieting

You could also set up your diet so you consume a very low calorie intake one or two days per week and eat normally on the other days. This is not technically considered intermittent fasting, but it is a similar style of eating.

How do you Do Intermittent Fasting?

Simply put, you decide how long you plan to fast all day and then plan your life around that schedule.

On a 16/8 hour fast, you may choose to stop eating around 8 pm in the evening and start eating again around noon. A sample day in the life on this type of fasting set up looks like this.

At 7 am you wake up, drink water, coffee, tea and diet beverages until your first meal. Then, at 12 pm, you eat about a third of your daily calories. Then you eat another two thirds of your calories at about 6 pm.

If you do a 20/4 daily fast, your schedule might look more like this. You fast from your wake up at 7 am until about 6 pm in the evening. Then you consume all your calories from 6 pm to 10 pm in a big meal.

If you choose to do an alternate day fast, you simply eat on some days with your normal schedule and then fast on other days.

Contrary to more rigid styles of eating, intermittent fasting sets up a few timing rules and lets you decide the rest.

What Results can you Expect with Intermittent Fasting?

Intermittent fasting can help you lose weight, reduce hunger and may improve focus or quality of life. For weight loss, aim for about .5 to 1 percent of your body weight per week. You will still need a reduced calorie plan to achieve these results. If you stick to this reduced calorie plan and intermittent fasting, you could experience weight loss in as little as one week. Within six to eight weeks, you may find you are more adjusted to intermittent fasting.

How Long Does it Take for Intermittent Fasting to Work?

In terms of weight loss, you can start seeing results in a week, provided you are following a reasonable calorie target for you. You might start finding other benefits such as improved focus, less hunger and cravings within the first few days as well. To determine whether it will work for you and your lifestyle, I would try intermittent fasting for at least 6 weeks.

How much weight can you lose in a month with intermittent fasting?

Similar to any calorie restricted diet, you can lose roughly 2-8 pounds per month with intermittent fasting. Heavier people can aim to lose weight at a slightly faster rate, about 1 percent of total body weight per week. It’s important to note that you can lose just as much weight with a more traditional eating schedule.

However, intermittent fasting can help with your dietary adherence to lose weight faster. 1 pound = 3500 calories, so losing 1 pound will require roughly a 500 calorie deficit per day. Losing 2 pounds per week will require a 1,000 calorie deficit per day.

Benefits of Intermittent Fasting

Many proponents of intermittent fasting rave about it. Here are some potential benefits of intermittent fasting.

Intermittent fasting is convenient. You can choose to fast in the morning or evening, or around your work or exercise schedule. You get a lot of flexibility to plan your fast as you wish.

You also save time with this style of eating. By eating one or two meals per day instead of four or five, you will probably save some time. This has a side benefit of helping you get more done during your day, because you don’t have to break regularly for eating, or cooking and clean up. You will probably also save time at the grocery store too if you only plan a few meals per week.

Additionally, you might even save money by just preparing one or two large meals per day instead of four or five.

Intermittent fasting can also give you more flexibility for social events. You can budget more calories for a single meal out with friends or for a date night.

By eating fewer meals, you might feel less hunger during the day, and it might be easier for you to maintain a lean physique. Larger meals are usually more satiating and fulfilling, which may make weight maintenance a bit easier.

If you are eating fewer calories due to eating fewer meals, you might also lose weight. For up to two thirds of Americans who are overweight or obese, this might greatly benefit their overall health.

Health Benefits

Fasting intermittently can help decrease insulin levels, which may help improve blood glucose control. This may help reduce your risk of diabetes or pre-diabetes or improve your glucose tolerance if you already have Type 2 Diabetes.

According the the New England Journal of Medicine, intermittent fasting in lab rats improved glucose tolerance. However, it’s still unclear whether these effects are observed in humans. Ketone bodies may actually serve as a signaling mechanism for the expression of other genes that have powerful disease fighting processes, according to the NEJM. This may mean improved insulin sensitivity and other powerful side effects for improved health.

Intermittent Fasting and Brain Health

Actually, intermittent Fasting may also reduce the risk of neurodegenerative and psychiatric disorders.

The production of ketone bodies during fasting windows may reduce the risk of neurodegenerative disorders, Alzheimer’s, Parkinson’s, Stroke, mood disorders and may boost brain health. Fasting may also reduce the occurrence of Alzheimer’s Disease and some cancers.

The production of ketone bodies during fasting may improve cognitive functioning and mental focus, and those benefits might extend to feeding windows as well, according again to the NEJM. Fasting is associated with greater balance and coordination, better verbal memory, spatial learning and memory, associative memory and working memory.

Intermittent fasting may also improve heart health, lower resting heart rate, improve heart rate variability, improve parasympathetic tone, reduce blood pressure and reduce the risk of heart disease.

Fasting and Cancer

Both intermittent fasting and caloric restriction may also play a role in cancer survival. Trials are underway to determine the effect fasting has on cancer growth for many different types of cancer. Fasting may improve survival for breast, colon, pancreatic, endometrial, ovarian and prostate cancer. Some research has shown fasting may be associated with suppressed tumor growth and extended survival in patients with glioblastoma.

Effects on Inflammation

Intermittent fasting may decrease inflammation and may improve stress tolerance.

The NEJM authors note that improved glucose tolerance may also decrease systemic levels of inflammation. Decreased inflammation can slow aging processes and the development of chronic diseasse.

According to Cabo and Mattson, “cells respond to intermittent fasting by engaging in a coordinated adaptive stress response that leads to increased expression of antioxidant defenses, DNA repair, protein quality control, mitochondrial biogenesis and autophagy, and down-regulation of inflammation.”

Because fasting can improve and decrease inflammation, it may also be useful in the treatment and disease progression of MS, asthma and arthritis. In patients with MS, intermittent fasting may play a role in controlling symptoms and affecting disease course.

Intermittent Fasting May Slow Aging

Your body is continually going through a process of breakdown and repair. Fasting may help accelerate this cellular repair and even slow down the aging process.

“During fasting, cells activate pathways that enhance intrinsic defenses against oxidative and metabolic stress and those that remove or repair damaged molecules,” note Cabo and Mattson.

If fasting is able to slow down the aging process, then it might improve longevity, quality of life or lifespan.

Intermittent Fasting and Fat Loss

Periodic fasting can potentially increase abdominal fat loss, independent of weight loss and compared to other types of calorie restricted diets.

Intermittent Fasting and Aerobic Performance

Actually, intermittent fasting may actually improve the results you get from aerobic training. It can help to enhance endurance performance more than endurance training under typical eating conditions. Lab rats with time-restricted feeding had better endurance than rats who had access to food at all times. Still, we do not know if these results are applicable to humans.

Increased Growth Hormone

Fasting is also associated with increased levels of growth hormone, a powerful hormone that helps you build muscle and burn fat.

Effects on Injury

Fasting may actually boost recovery from spinal cord injury, other injury, and surgery.

Interestingly, fasting may improve healing from traumatic injury and improve functional outcomes for both brain and body.

According to the NEJM, “several studies have shown beneficial effects of intermittent fasting in animal models of traumatic head or spinal cord injury. Intermittent fasting after injury was also effective in ameliorating cognitive deficits in a mouse model of traumatic brain injury.”

More Research Still Needed

While many of these claims about intermittent fasting are exciting and compelling, scientists are still in the research stages to determine if fasting really does boost health and longevity. There are still many unanswered questions about intermittent fasting. Are studies performed on other animals like laboratory rats even pertinent to humans? How much of an effect does fasting have on human health? Is fasting comparable to calorie restriction, or simply eating a healthy diet? Can the results of these promising studies be replicated over longer time periods? Does fasting have unexpected negative or mixed consequences? Do any studies show conflicting results of fasting, and if so, can these results be reconciled?

Drawbacks to Intermittent Fasting

Despite its proposed health benefits, intermittent fasting might not be a good fit for everybody. Here are some considerations to keep in mind before getting started with intermittent fasting.

At first, you might feel more tired, grumpy, light-headed or low energy> during your fasting windows as your body adapts.

Fasting and Workouts

Working out might be hard during a fast. While some people feel they can get used to fasted training, the reality is that most sports dieticians recommend entering each workout in a state of calorie and protein balance. While you may be able to acclimate to training in a fasted state, it probably is not ideal for hard training, or for optimal performance.

Gaps in energy intake might lead to trouble focusing later in the day, fatigue later on or even impaired workouts. Some studies find that even when athletes work out later in the day, missing breakfast can impair their performance, even if they compensate for the total calorie intake later.

Fasting may Reduce Daily Energy Expenditure

Fasting can reduce energy expenditure. This may cause decreases in metabolic rate and energy needs.

Fasting May Cause Muscle Loss

Muscle loss may occur. Studies of intermittent fasting have shown mixed results regarding body composition, fat mass and muscle maintenance/growth. Intermittent fasting might not be optimal for muscle growth or maintenance, compared to more traditional eating schedules where protein and energy are more evenly distributed and large energy deficits are avoided.

This may be especially true for older individuals, who might respond better to evenly distributed protein intake throughout the day for muscle growth. Intermittent fasting can down-regulate the production of mTOR, a signaling molecule that is associated with muscle protein synthesis and muscle growth.

Fasting and Eating Disorders

Finally, this type of eating may not be appropriate for those with eating disorders. Intermittent fasting may discourage adherence to a normal dietary calorie intake and pattern. For those with bulimia or binge eating disorder, fasting for long periods of time may encourage binges or binge and purge type behavior later.

Conclusions

Intermittent fasting is just beginning to get some attention and is currently the focus of a number of clinical trials, but also a lot of media attention. It may indeed be responsible for many superior health outcomes and might even enhance your health or fitness. We do not know for sure, however, that intermittent fasting is the next big thing for superior health and longevity.

Whatever the case, now you have a lot more information to make an informed decision whether intermittent or periodic fasting is right for you. And if you are still confused whether or not to try this style of eating, you can always talk to your doctor or even a registered dietician to help decide what style of eating would be best for you.