It’s not a new concept, but many people have yet to experiment with intermittent fasting. So, let’s go over what it is, why it’s used, who should do it, and who shouldn’t – so you can figure out if it’s something you’d like to implement in your lifestyle.
What is Intermittent Fasting?
Intermittent fasting is an umbrella term for different ways to schedule eating times. The more general term used is time restricted eating, which means that someone will go without food or drink (other than water, tea, non caloric liquids) for a certain period of time, eat within a feeding window, and begin the fasting process again. When done correctly, people can still do time restricted eating and meet their needs for essential needs because fasting doesn’t restrict how much one can eat, but rather when and for how long someone can eat.
The three most popular types of intermittent fasting are:
Alternate-day fasting – day of normal eating followed by day of 500kcal or less, and repeats
5:2 fasting – done on a weekly-basis; 5 days of eating normally, and 2 days of complete fasting
Daily time-restricted fasting – what people usually refer to when they say “intermittent fasting.” Eating normal amounts daily, but within a window of time and fasting for the rest of the hours of the day. The most popular type of time-restricted fasting is 16 hours fasting, with an 8 hour window of eating. Others choose to do 14/10, 18/4, and 20/4.
Why is it Popular?
Many use intermittent fasting as a useful tool for weight loss, because the narrow eating window often results in lower calorie consumption overall. However, it has many other benefits beyond weight loss.
Fasting has been found to help fat loss. The body’s metabolism turns to ketones, which is stored in fat, for energy when it no longer has any more glucose to burn (which comes from food). It’s also been shown to improve many biomarkers associated with chronic diseases like diabetes, heart disease, multiple sclerosis, and cancer.
Others also use intermittent fasting as a way to stay focused and be more productive with work as a morning meal can make the mind sluggish. This happens as a result of more energy and blood directed to the stomach and intestines to aid with the taxing process of digestion. Think about how after a large meal, a nice long nap seems very enticing.
Who Might Benefit from Fasting?
Intermittent fasting is certainly not required to live a healthy lifestyle and to have balanced, nutritious, and nourishing eating habits. However, it has been found to be beneficial for a few groups of people.
Treatment of heart disease
Researchers have come up with three different ways intermittent fasting improves cardiovascular health. The first way is that lower calorie consumption may also lower inflammation. The second is that late night eating has been shown to increase LDL (bad) cholesterol levels in just two weeks, suggesting that our body’s organs and systems function optimally at certain times of the day. The third way is by inducing ketogenesis, where the metabolism no longer has glucose to run off of so it switches to fat stores (as well as some muscle) for energy via ketones. This switch of energy lowers LDL and increases HDL (good) cholesterol.
Neurodegenerative Disease (Alzheimer’s & Parkinson’s) or Brain Aging
The health span of the nervous system is the years of time that are spent in good cognitive health. Fasting can help cellular and metabolic pathways which increases one’s health span. The reason for this is that calorie restriction and time restrictive eating both assist in increasing the body’s ability to protect neuronal damage and death, promote repair, and increase stress resistance, which increases one’s health span. The stress of metabolic breakdown in the body have been shown to give rise to Alzheimer’s and Parkinson’s disease, so fasting may lower one’s risk, as long as they are still eating an adequate, nutritious diet.
People with or at Risk of Diabetes
Fasting has been shown to aid in diabetes as well. Studies support that we may be able to break down nutrients better in the day time rather than in the evening. Meals eaten later in the day, then, can cause higher blood sugar spices. Because daytime time restricted eating is more likely to go along with eating most food in the day and none late at night, it can help the Circadian rhythm of insulin (the hormone that helps lower blood sugar after a meal) and the blood sugar.
But this is only if the participants eat meals early in the morning and finish before evening. Eating late can disrupt sleep, which in turn lowers insulin’s ability to regulate blood sugar levels. Time restricted eating also requires a strict eating schedule that can help individuals maintain regular meal timing. Irregular meals can reduce insulin sensitivity, so using fasting to regulate meal timing can help with blood sugar regulation.
However, when not careful or consulting with a physician thoroughly, participants may be at a higher risk of hypoglycemia, dehydration, and low blood pressure. So it’s best to err on the side of caution before attempting any heroic measures until you know it’s safe for you.
Who Should Not Fast?
Although intermittent fasting has a lot of benefits and may be very healing and helpful for some, there are a few groups of people who may want to stay away from fasting. Every person is different and will function in a different means than another, so each body will have different needs as well.
People in Specific Life Stages
Over time, intermittent fasting results in approximately 20-30% reduction of caloric intake. Those with higher caloric needs should not practice intermittent fasting because they are more likely to fall short of their caloric need. This is especially true for those going through a stage of growth and development in which adequate energy is vital:
- Pregnant & breastfeeding mothers
- Children under 18
- Underweight individuals/those trying to gain weight
Women Trying to Regain Their Period
Women who have lost their period due to hypothalamic amenorrhea – most typically caused by excessive exercise, restrictive/restricted eating, stress, and rapid weight loss – are not recommended to fast or follow any certain non-therapeutic diet. It is actually recommended that women trying to restore their menstrual cycle eat a minimum of 2500kcal/day. This is not conducive with alternate-day or 5:2 fasting which includes days of 500kcal or less.
A study comparing athletes who consumed and burned the same amount of calories showed that periods of restriction (ie. fasting) negatively impacts one’s menstrual cycle. Those who were in a fasted state for 4 or more hours during the day did not recover or have their period. Those who did eat at regular intervals throughout the day and exercised the same amount had a regular cycle.
Individuals with a History of Disordered Eating.
Any form of restrictive eating (including time-restrictive eating) could perpetuate disordered eating behaviors. A strict schedule requires the individual to be hyper-focused on eating behaviors, which is the opposite goal of recovery. Eating disorders are often characterized by a need for excessive control, which may be promoted by fasting. It is recommended that both women trying to regain their period as well as those with a past of disordered eating work with a dietitian and physician to make sure they are nourishing themselves adequately for their condition.
Last Thoughts on Intermittent Fasting
There are many factors to take into consideration when determining if fasting is right for you. Some of the health benefits are well studied, such as those regarding weight-loss and cardiovascular disease, but others need more research, such as diabetes. Although many of the benefits actually arise from the inherent reduction in calories, others seem to be related to adhering to our circadian rhythm (natural sleep/wake cycles).
These benefits aren’t exclusive to fasting. Weight loss and better sleep are definitely attainable without fasting, but some choose to use the path of fasting on their hike to Health. No matter what you choose to do, it is always best to work with a healthcare professional and/or dietitian who can assess individual needs before implementing any major dietary changes.