Intermittent fasting has become increasingly more popular as a diet trend over the past few years. To partake, participants cycle between phases of eating and fasting on a predetermined schedule.
The Health Insider team decided to look into this phenomenon to try to determine if this is another passing fad or has some legitimate findings behind it.
A study from NIH reports intermittent fasting should be undertaken no more than three times per year until more research has been conducted.
In fact, it goes on to suggest that fasting for longer than this recommended period of time has little evidence of extra health benefits.
Fasting for too long at a time can also make participants overeat during their eating cycles, negating the benefits of the fast.
Overall, the study concluded that properly maintaining intermittent fasting can reduce body fat, lower blood pressure, and reduce risk factors for age related diseases.
So, how does intermittent fasting work?
Fasting periods activate pathways in the cells that decrease the effect of various types of stress on the body by increasing stress resistance and suppressing inflammation, according to the New England Journal of Medicine. It removes or repairs damaged cells during this time.
Intermittent fasting is a method of calorie restriction (CR). CR (20-40% fewer calories than maintenance) can prevent aging related diseases such as diabetes, cancer, and atherosclerosis.
The study continues that CR promotes proper cellular functioning which can prevent biological aging, thereby increasing lifespan.
By maintaining a stable oxygen level within the cells, CR can prevent overoxidation which causes cellular stress.
This stress can lead to the development/exasperation of various diseases. By regulating oxygen levels, CR can delay age related loss of functioning in the cells.
The NEJM article also raises the following possible benefits of intermittent fasting::
- Improved spatial memory, associative memory, and working memory
- Improved cardiovascular health
- Reduced risk of neurodegenerative disorders (Alzheimer’s, Parkinsons, stroke, etc.)
- Reduced tumour growth and protection against cancer
- Reduced tissue damage
But I’d get so hungry!
An option for those who can’t fathom the idea of the hunger they’d experience with fasting for 12+ hours, there’s what’s called the “Fasting Mimicking Diet” (FMD).
The study from NIH says the FMD is a diet of food which is low in calories, sugars, and protein but high in unsaturated fats and micronutrients.
Many salads (if you’re careful with the dressing) are a great example of FMD meals. They can be packed with micronutrients and tailored to personal taste and dietary requirements.
The California Center for Functional Medicine breaks down how to calculate your personal dietary needs and offers a few FMD approved recipes.
Another option is purchasing ProLon, a nutrition program developed by Dr. Valter Longo, the creator of FMD. With no calculations necessary, the five-day program is delivered with the ingredients you need to successfully fast.
To follow intermittent fasting using FMD, instead of just sticking to water during fasting periods, you can eat small amounts of FMD foods to tide you over.
Then, during the eating periods, you can eat as you normally would for a healthy diet. This keeps your body in fasting mode according to the predetermined schedule, but can stave off hunger pains.
How should I fast?
To be effective, the fasting period must last for at least 12 consecutive hours. The NIH study suggests that the body will not go into fasting mode until this amount of fasting time has elapsed, so don’t kid yourself about going hungry for any less.
NIH recommends no more than a three month long fasting period before returning to a regular eating schedule.
The goal of intermittent fasting is to reset your gut’s microbiome. NIH states that benefits of intermittent fasting can last for months after completing a fasting period. So, it doesn’t have to be a lifelong dietary change. Rather, it can be repeated up to a few times a year.
During the three month fasting period, NEJM states that the most widely studied fasting intervals are:
- Alternate day fasting
- Eat a normal diet one day, fast or FMD with less than 500 calories the next, and repeat.
- Daily time restricted fasting
- Eat a normal diet within an eight hour time period and fast or FMD for the other 16 hours of the day.
- 5:2 fasting
- Fast or FMD for two days and eat a normal diet for five days.
Not every fasting period will work for every person. Certain time frames may cause excessive hunger and irritability.
Another study cites a minimum of a week long commitment at a time is required to be effective. There have not been many studies on the efficacy of short-term intermittent fasting, and results may be minimal if fasting within this timeframe.
Are there side effects to fasting?
Mayo Clinic lists possible side effects of undertaking intermittent fasting:
- Hunger (no kidding!)
If the effects do not go away after a month, stop fasting. Talk to your doctor if they are severely impacting your quality of life.
Eating disorders – Anyone with an ongoing history of eating disorders should not attempt intermittent fasting, according to Johns Hopkins Medicine.
Food is not a bad thing – Seeds of Hope, an eating disorder treatment clinic, writes on their website: “When you begin to associate not eating with weight loss, it’s easy to acquire a fear of food. Your brain rewards you for starving yourself and can develop anxiety about mealtimes. It’s difficult to balance the healthy idea of eating for nourishment with the idea of fasting to lose weight.”
For adults only – Both John Hopkins and NIH agree that children under 18 should not partake in intermittent fasting as it promotes growth retardation and can disrupt normal development.
Eating for two – John Hopkins and NIH also caution expecting and nursing mothers. Growth retardation can affect fetal and infant development in the same ways it affects children. Fetuses and breastfeeding infants take their nutrients from their mother, and a fasting diet will not provide enough essential nutrients for the child to develop.
Type 1 diabetes – Although studies have been conducted on people with type 2 diabetes, currently there is no information on how it interacts with type 1 diabetes, according to Johns Hopkins. It is therefore suggested to refrain from intermittent fasting if you have type 1 diabetes, until there is more information available.
Diabetes Canada recommends: “Fasting can be done safely for those who take insulin, if the treatment is individualized and adjusted. Other diabetes medications used by people with type 2 diabetes may need to be adjusted one to three months before [starting].” They urge patients to stay in touch with their doctor throughout the entire process.
Considering intermittent fasting?
- Talk to your doctor about it and request that you be supervised during the process. Your doctor may have some suggestions for you given the understanding of your pre-existing medical conditions, prescriptions, etc. Intermittent fasting will impact people in different ways and could be a danger for certain patients with pre-existing conditions such as autoimmune disorders.
- Remember too that not all doctors are trained to prescribe intermittent fasting periods, but can help make sure you stay healthy during the diet. When attempting this diet, stay in tune with your body and hunger cues.
- There is no one-size-fits-all when it comes to eating, and keeping up to date with current research and guidelines from legitimate sources will help you have the best fasting experience possible.
Overall, studies seem to indicate that intermittent fasting leads to Improved gut functioning, with in turn creates a multitude of benefits for the mind and body. Intermittent fasting can be a great way to promote longevity and ward off some age related illnesses when pursued properly and responsibly.
Given the relatively short period of time that intermittent fasting has made its way into mainstream dialogue, it should come as no surprise that while the findings so far are very encouraging, there is still much more to understand with respect to the relationship between intermittent fasting and the gut-brain axis.
The Health Insider will be watching this area of study with great interest, as more information comes to light.