If you are like most people, you’ve heard the buzz about Intermittent Fasting (IF), and you’ve probably wondered if it’s something you should consider. Maybe you’re even confused about how it works or whether or not you’re already doing it. After all, don’t we fast every night when we sleep? I’ve been getting asked a lot of questions about fasting recently so I thought it would be a valuable topic to discuss.
Let’s begin with defining what IF is.
The concept of fasting has been around for centuries, and originated in different cultures due to certain religious practices. Traditional fasting is defined as the abstinence of food or drink. Intermittent fasting is a modified version of a traditional fast. It is defined as a period of time in which you cycle between a period of fasting and eating.
There are different variations to the fasting cycle. Some of the most common ones are:
- Alternate day fasting (5/2)– This is a cycle in which a person will eat a normal diet for five days and then fast for two days. During the two days, you don’t fast completely, but you severely limit calories. So that might look something like this: Breakfast – Fast, Lunch – Fast, Dinner – 500 calories or less.
- Complete fasting – This is a fully restricted fast that can last up to an entire day. The other days of the week a normal diet is consumed.
- Time restricted feeding – This is probably the most popular type of IF. This involves fasting within a certain number of hours per day, and eating within the remaining timeframe. The most common is 12/12 (eating all meals within a 12 hour window and fasting for 12 hours) or 16/8 (eating all meals within an 8 hour window and fasting for 16 hours). The cycle can be repeated as often as you prefer – either every day or just a couple of days per week.
Recent studies have reported several benefits to IF. IF has been shown to:
- Assist in alleviating digestive disorders (IBS, SIBO)
- Improve insulin resistance and blood sugar balance
- Support weight loss
- Slow the growth of certain diseases such as Type 2 Diabetes, cancer, metabolic syndrome, cardiovascular disease, and obesity
- Lower inflammatory markers
- Improve longevity
- Support cognitive function
- Improve circadian rhythm (the body’s natural sleep/wake cycle)
Some of the most interesting research has been done in the area of weight loss, cardiac health, and the microbiome.
The idea behind IF supporting weight loss is due to the notion that IF promotes calorie restriction and a temporary increase in resting energy expenditure. In addition, fasting has been shown to support a decrease in fat mass while allowing the body to maintain muscle mass. The theory behind these findings is that during a fasting period, fatty acids are released from fat cells and enter the liver where they are converted to ketones and used for energy and neurons. However, to date this idea has only been studied in animals, so more studies are needed to determine if it applies to humans as well. Other studies have shown that fasting allowed for a greater loss in abdominal fat and overall fat mass.
Alternate day fasting has been shown to have a significant reduction in triglycerides, LDL particle size, inflammatory markers such as CRP and may prove to be a viable option for those who are overweight or obese and suffering from cardiovascular disease.
Another study found that participants who engaged in time restricted eating (16/8), resulted in a 3% decrease in body weight as well as reduction in blood pressure. The researchers concluded that this type of fasting allowed for weight loss without calorie counting. This type of diet is less restrictive then complete and alternate day fasting and may be easier in terms of compliance.
Studies have shown that a diverse and healthy gut can be beneficial to maintaining a healthy weight. In certain cases, obese individuals have been found to have higher levels of harmful bacteria in gut, and low diversity of good bacteria. In addition, we are now learning that the gut has its own circadian rhythm. Chronically disrupted circadian rhythm may affect GI function and impair metabolism. Obesity or weight gain can be impacted by circadian rhythm in our microbiome. The microbiome in obese patients require a greater amount of energy, and imbalances can lead to chronic inflammation, dysbiosis, and intestinal permeability all of which can contribute to obesity.
How does fasting come into play? Fasting promotes gut rest, allowing the Migrating Motor Complex (MMC) to work optimally, sweeping debris from the small intestine into the colon and allowing proper digestion and absorption. This can be highly beneficial to those suffering from certain GI disorders and optimizes the ability to have a healthy well functioning gut.
- In multiple studies, compliance was the biggest issues for participants. For those who engaged in a 5/2 alternate day fast, intense hunger on fasting days was the biggest reason for non-compliance.
- In addition to hunger, other possible side effects are weakness and fatigue.
- IF is simply not practical for everyone, since the benefits will only occur with a consistent eating/fasting period over time. If your schedule varies throughout the week, IF may not be a viable option for you.
- Due to intense hunger encountered during an 8/16 fast, some individuals report consuming higher amounts of food than normal and higher calorie amounts, which could lead to disordered eating patterns, weight gain, and digestive discomfort.
- Due to lack of studies, we have no evidence to know what this does to a person’s metabolism long term.
IF is NOT recommended for the following individuals:
- Those with certain conditions such as hypoglycemia, hypotension, advanced Diabetes, and those with high cortisol/adrenal dysregulation
- Individuals with a history of eating disorders or those at risk of an eating disorder
- Individuals who are underweight, or are looking to gain weight
- Pregnant or breast feeding women
The bottom line:
I prefer the idea of a 12/12 fast. Consume a healthy balanced diet within a 12 hour window, and allow for gut rest and calorie restriction within a 12 hour fast. This seems to make the most sense to me, and allow for the most compliance without feelings of deprivation and intense hunger.
It is also important to understand that IF is not an excuse to go crazy and eat whatever you want during the eating portion of the cycle – a common misconception. Individuals should still strive to maintain a healthy balanced diet, full of lean proteins (poultry, fish, eggs, lean pork and grass fed beef), healthy fats, plenty of fruits and vegetables, and complex carbs (starchy veg, whole grains, beans and legumes). If you are contemplating IF, talk to a qualified health professional to determine if it’s right for you. If you have further questions about IF, contact me here