In this article:
- What is intermittent fasting?
- Types of intermittent fasting
- Benefits and risks of intermittent fasting
- Is it safe for your thyroid?
Humans have fasted for a variety of purposes throughout history. Fasting has been used for therapeutic, religious, and political purposes, as well as during times of food scarcity. Health benefits from fasting were recognized and documented as early as ancient Greek civilization. Indeed, fasting is very much a part of the history of our species as hunter-gathers did not have a steady flow of available food. Recently, intermittent fasting has become popular because it may have many health benefits.
What is intermittent fasting?
Intermittent fasting (IF) is when a person follows a cyclical pattern of eating and fasting. Unlike diets where certain foods are restricted, intermittent fasting is an eating pattern based on the time between meals. There are different patterns of intermittent fasting that a person can follow.
People do intermittent fasting for a variety of reasons. For health purposes, people may choose to fast to lose weight, control inflammation, decrease insulin resistance, and improve brain function. Intermittent fasting for religious purposes may be to cleanse the body or as a demonstration of sacrifice. For example, the season of Lent is a time of fasting for many Christians who observe this tradition. Similarly, Ramadan is a month-long period of fasting for Muslims.
Types of intermittent fasting
People who fast intermittently for health purposes have several different eating cycles or patterns they may choose to follow. Some IF schedules cycle around a 24-hour window, whereas others may span a week.
5:2 Fasting
People eat typical meals and portions for five days per week. On the other two days of the week, calorie intake restricts to about 500 calories for the day. For example, a person may choose to restrict calories on Tuesday and Friday by eating two small meals that are equal to about 250 calories each. Your caloric requirements on fasting days may depend on any health conditions or if you are male or female.
The 16/8 Method
This type of IF involves fasting for 16 consecutive hours, followed by 8 hours for eating. Typically, most people stop eating by 8 pm and do not eat until noon the following day. Women who follow this pattern tend to do better fasting for 14-15 hours. To curb morning hunger pangs, you may drink zero-calorie beverages, including water and coffee (without the sweet and creamy additives).
Overnight fasting
Fasting for 12 hours is one of the most accessible types of IF to follow, as most of us do this naturally. Overnight fasting cuts out late-night snacking, which can be beneficial to your weight and metabolism.
Alternate-day fasting
This is a popular choice for people seeking weight loss results. In this method, you repeat a cycle of eating one day and then fasting the next day. Some people who follow this method of IF may choose to eat a small number of calories on fasting days.
Whole-Day Fasting
In this method, you eat one large meal per day, resulting in 24 hours of fasting. For example, some people choose to eat one large dinner and then do not eat until dinner the next night.
Benefits of intermittent fasting
Adequate fasting, especially during sleep, is essential for metabolic homeostasis. It enables blood sugar and insulin to return to baseline levels.
Eating without adequate fasting may result in sustained hyperglycemia (high levels of sugar in the blood) and elevated insulin secretion. High blood sugar levels impair normal cell function and cause inflammation, which increases insulin resistance. Insulin is a hormone produced by your pancreas that moves sugar from your blood into cells for energy. Insulin is also involved in energy storage.
Although cells become resistant to insulin's role in blood sugar uptake, they stay responsive to the hormone's role in fat storing. This effect is why insulin resistance and high blood sugar levels are associated with increased body fat.
The most common reason people do intermittent fasting is for weight loss. Studies indicate that fasting causes hormonal changes that use stored fat for energy in the absence of continuous food consumption. Along with weight loss, there are several health benefits associated with intermittent fasting, including:
- Boosting your metabolism by increasing your levels of norepinephrine
- Correcting unhealthy eating behaviors
- Reducing your risk for cardiovascular disease by decreasing your LDL and lowering high blood pressure
- Decreasing inflammatory markers that can lead to chronic illness including autoimmune conditions and cancer
- Improving blood sugar control by reducing insulin resistance
- Increasing human growth hormone (HGH) secretion, which helps with building muscles, weight loss, and increasing metabolic activity
Risks of intermittent fasting
There are also risks associated with fasting. For instance, people with diabetes or blood sugar control issues may be at risk for low blood sugar levels (hypoglycemia) when fasting, which can be life-threatening.
However, for most, the primary concern with intermittent fasting may be sustainability. Figuring out how to fit fasting into your work, social, and health routine can be challenging, especially for those who keep unusual hours or lack routine. With any eating method, the goal should be consistency and overall health for the long haul.
For some, intermittent fasting may lead to new or trigger previous disordered eating behaviors.
Remember that the more dietary pressure you put on yourself, the more likely you are to experience inflammation. This inflammation can worsen your autoimmune reactions or interfere with your thyroid function. For this reason, we recommend finding a way of eating that you can manage in the long-term.
Children, endurance athletes, underweight people, and women who are trying to conceive, pregnant, or breastfeeding should avoid intermittent fasting. Also, people with a risk for malnutrition, such as those with vitamin deficiencies, should not fast.
Is it safe for your thyroid?
Each of us is unique with individual sensitivities. Intermittent fasting can be safe for some people with thyroid disease, whereas others may experience adverse effects. Because the thyroid is the metabolic powerhouse of the body, fasting impacts the thyroid directly.
A recent study evaluated the effects of alternate-day fasting in healthy people. Compared to the control group, those who alternated 36 hours of zero-calorie intake with 12 hours of unlimited eating showed lowered levels of triiodothyronine (T3). Other studies also suggest that eating a low-calorie diet may cause a decrease in T3.
Another study compares the weight-loss efficacy of alternate-day fasting versus daily calorie restriction in adults with subclinical hypothyroidism. After six months, results showed a similar bodyweight decrease by both alternate-day fasting and calorie restriction. Insulin resistance decreased more with Alternate-day fasting than calorie restriction. TSH and fT4 remained unchanged.
Intermittent fasting may increase the metabolism of your thyroid medications. It also changes the way your body uses energy. If you have Hashimoto's disease, well-timed intermittent fasting may improve inflammation and reduce the severity of this autoimmune condition.
If you are considering using IF for weight loss and other health benefits, talk with a doctor to learn if intermittent fasting is the right choice for you.
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How to apply this information
As the saying goes, everything in moderation. Some 42 million Americans go on a diet each year and don't succeed. We recommend you apply the information in this article to core nutritional principles.
Avoid processed foods and added sugars
Focus on nutrient-dense, whole foods like fruits, vegetables, beans, lean proteins, and healthy fats.
Let your body burn energy between meals
Don't over-snack between meals and move your body throughout the day.
Consider a simple form of intermittent fasting
Choose hours of the day between which you eat. For instance, between 7 am, and 3 pm, or between 10 am to 6 pm.
Eat breakfast to fuel your day
Eating breakfast is essential to fuel up for your day. Research suggests that you attain a fasting state for a certain period each day. So, it may be advisable to avoid late-night snacking or eating to give your body time to rest.
Avoid snacking or eating at nighttime
Studies suggest that the habit of late-night eating may cause higher odds of metabolic syndrome and abdominal obesity.
A note from Paloma Health
If you are considering intermittent fasting, make sure to talk to your care team. A Paloma Health thyroid doctor or thyroid nutritionist can help you create a customized eating plan to optimize your thyroid health.
