What is Intermittent Fasting?
As the name implies, Intermittent Fasting (IF) diet involves a fast, however, the 'intermittent'part is what differentiates this from annual religious fasts you or someone you know may have partaken in at some point. Intermittent Fasting is a broad term for various protocolsthat involve cycling between a fasting period and a non-fasting period. During most intermittent fasts, you have a smaller time window during which you can eat (usually fewer than 8 hours), and you fast for the remainder of the day. These fasts are typically longer than the overnight fasting that happens when you are sleeping, and range from approximately 16 hours to any number of days (generally thought of as more prolonged fasting).
Prolonging the fasted state beyond sleep has been shown to have a multitude of health benefits such as improving blood glucose regulation, boosting energy, increasing growth hormone production, reducing inflammation, decreasing oxidative stress, lowering triglycerides and blood pressure, enhancing and protecting brain function, increasing resistance immune disorders, cancer, heart disease, stroke, eye disease, Alzheimer's disease and promoting longevity.
Many of these studies are rodent based as conducting this type if experimentation on humans can be challenging due to many influencing factors. The research done on human subjects is limited, but does show some exciting results as a possible approach to benefiting human health. It is important to understand that the research had mixed results, and clear conclusions of the benefits of IF still do not exist in the scientific world.
Common Types of Intermittent Fasting
There are numerous Intermittent Fasting programs, with the most popular being alternate-day fasting, whole-day fasting and time-restricted feeding.
This is the most researched form of IF, which requires alternating between feeding and fasting days. Fasting days typically comprise of 1 meal at lunch of approximately 25% of individual caloric needs. This could be considered 'modified fasting', which has different durations/periods of fasting from anywhere between 30-40 hours, based on personal needs and schedule.
Feeding days comprise approximately 100% of individual caloric needs. Any type of nutrition protocol can be followed on both 'fasting' and 'feeding' days, although as a Paleo advocate, I believe and strongly support the consumption of whole, real foods for optimum health and wellness.
Fasting (either totally avoiding food or severely restricting caloric intake) for 24 hour periods one or more days a week is referred to as whole-day fasting. This is commonly known as the 5:2 diet, in which the 5 represents the number of days you eat normally, and the 2 represents the number of non-consecutive days that calories are restricted to 25% of individual caloric needs.
This is fast becoming the most popular type of IF and requires fasting for a specific number of hours each day. A very popular form of this time-restricted feeding program consists of a fasted phase lasting 16-20 hours, followed by a feeding phase lasting for the remainder of hours in a 24-hour period. This form of fasting can be followed as a type of daily routine or just on specific days.
When considering implementing an IF protocol, it is important to consider all the benefits and drawbacks on an individual basis to determine whether IF is right for you.
Benefits of Intermittent Fasting
Promoting Health & Weight Loss
Results in several human studies have found Intermittent Fasting has been associated with a significant reduction in body weight, body fat, and waist circumference in both the short and the long term.
Although some of the weight loss may be lean muscle mass, individuals following an IF protocol have been shown to lose more fat mass while retaining more of their muscle tissue compared to daily calorie restriction-type of diets.
Further benefits of IF include an improvement in asthma symptoms by lowering airway resistance, oxidative stress and inflammation, increased insulin sensitivity and blood sugar control as well as significant decreases in total cholesterol and LDL, blood pressure and triglyceride levels.
Improved Brain Function
Other studies have explored the powerful effects of this time-restricted diet on cognitive performance (such as memory), which has been found to be beneficial especially for athletes whether they are exercising or at rest.
No Emphasis On Caloric Restriction
You can still eat the same number of daily calories, or better yet, when following a nutrient dense Paleo diet, you can still listen to your body without worrying about calories. No need to change or remove any of the foods you eat. The nutrient density of your Paleo/Primal/whole foods based diet will further enhance any of the benefit experienced with IF.
This eating pattern is easily implemented and for those who like routine, with a high rate of compliance compared to the traditional calorie restriction is difficult long term. For some, it may be easy to incorporate into the current routine with little concern about limiting the types and amount of food you eat on feasting days. You may already practice IF to some degree as time-restricted feeding is often unintentionally practiced by those who skip breakfast and do not eat after an early dinner.
Larger (More Satisfying) Meals
Many prefer consuming a larger portion of food at one time as it can leave one feeling more full and satisfied, both immediately and over a longer period of time. This can be further enhanced by choosing whole, nutrient dense, Paleo-friendly foods which support long term satiety. Intermittent Fasting can actually help prevent the typical evening binge on foodafter not eating all day at work, or the sooner-or-later binge-eating, resulting from those calorie-restricted diets that are difficult to keep up with for life.
Drawbacks of Intermittent Fasting
You are well-aware that life is unpredictable and circumstances beyond your control often appear. Changes and stressors can lead to unexpected feelings of hunger and lack of productivity; especially if you are used to eating lots of snacks or meals throughout the day, and suddenly embark on different meal timing. Some may also experience a lack of energy or motivation to be active and do the things they generally enjoy. Studies on breakfast consumption have shown positive outcomes such as promoting cognitive and academic performance, as well as weight-loss maintenance in various individuals. Getting enough fuel throughout the day can help keep you in good spirits, energetic and productive.
Larger volumes of food translates to more time needed to digest, which causes additional stress on your GI tract, leading to indigestion and bloating. This can have great implications for those struggling with IBS, who already have a more sensitive gut, inflammation of the GI, disturbed bowel movements, and are therefore more susceptible to cramping, abdominal pain and bloating. With IBS, difficulty obtaining all the nutritional requirements due to uncomfortable symptoms that accompany eating, are recommended to eat at regular times, take time when eating, and not skip meals in order to have regular bowel functions.
Bingeing And Over-Eating
Since you only have a limited amount of time reserved for eating, some people may take the feasting periods as an opportunity to eat more than they really need. When you are hungry or anticipate a period of fasting coming up, it can be very tempting to over indulge when food is available. If the fasting element of the Intermittent Fasting process were to create some sort of caloric deficit, it is very possible that the feasting period easily undo it.
Lack Of Results
Although a previously mentioned study showed greater lean muscle retention with Intermittent Fasting, the research here is mixed. Other studies have foundno significant difference between continuous calorie restriction and fasting on parameters like weight loss, fat mass, fat-free mass, glucose homeostasis, cardio-protection, and appetite regulation.
Intermittent Fasting For Women
For women in particular, if Intermittent Fasting is taken too seriously and excessively restricts energy and protein, a real risk of nutrient deficiencies, electrolyte abnormalities and issues with fertility and reproduction may develop.
Intermittent Fasting is possibly linked to issues with menstruation, fertility, metabolism disruptions and early menopause in woman. According to animal studies, fasting led to decreases in body weight, blood glucose levels and reduced ovary size, thus significantly impacting fertility. Additionally, women typically eat less protein compared to men, and fasting women, even less. Low protein consumption means less amino acids that are needed to activate estrogen receptors and produce IGF-1 (Insulin-like Growth Factor); responsible for triggering the lining of the uterine wall to thicken and begin the reproductive cycle process. Furthermore, a shifted estrogen balance will change metabolic activity and impact digestion, protein turnover, bone formation, recovery, growth, cognition and mood.
Is Intermittent Fasting For You?
If you have a medical condition, it is the best to avoid this type of fasting because it may have the opposite effect on your health. If you are diabetic or hypoglycemic and need glucose throughout the day, going without can have dangerous effects. If you struggle with thyroid or adrenal issues (whether you are medicated or no), it is best to avoid IF. If you are one of those people who feel nauseous or just does not do well with prolonged periods of not eating, Intermittent Fasting is not suitable for you. It is also important to mention that if you have ever had a history of an eating disorder, Intermittent Fasting is definitely not for you. Since IF causes you to eat more food in a short amount of time, it may exacerbate potential disordered eating patterns such as a binge-eating mentality. This may cause eating more food than your body can handle, or a restrictive mindset that is caught up with IF due to the desire to limit food-intake for the sole purpose of weight loss. This could have adverse effects on your relationship with food and your body’s physical health.
Pregnant and breastfeeding women and children should never practice Intermittent Fasting.
Many potential health benefits have been observed from Intermittent fasting, but there are current limitations of intermittent fasting research and mixed results found in the different types of intermittent fasting. Intermittent fasting can be seen as an alternative to, or an additional resource when following a nutrient dense, whole foods based program like the Paleo diet. When it comes to food, there is definitely no one-size-fits-all approach and it is important that you assess your own eating habits and find out what approach works best for you.