What is Intermittent Fasting?
The last 2-3 years has seen intermittent fasting become one of the most popular health and fitness nutritional trends. People are predominantly using it to lose weight and improve their overall health. Studies have shown that it can have powerful effects on your body and brain and potentially longevity.
Intermittent fasting is an eating pattern that cycles between periods of fasting and eating. It doesn’t specify which foods you should eat but rather when you should eat them, so is more accurately described as an eating pattern than a diet.
Two common intermittent fasting methods involve daily 16-hour fasts or fasting for 24 hours, twice per week. Fasting has been a practiced throughout human evolution. More out of necessity than intentional as for ancient hunter-gatherers food availability varied year-round and often they couldn’t find anything to eat. As a result, humans evolved to be able to function without food for extended periods of time.
There are several different ways of doing intermittent fasting, all of which involve splitting the day or week into eating and fasting periods. During the fasting periods you generally consume nothing but water and often black coffee or tea.
Leangains protocol or 16/8 method involves skipping breakfast and restricting your daily eating period to 8 hours, such as 12–8 p.m. Then you fast for 16 hours in between. This is also often called time restricted eating and some people take it further by reducing the eating window down to 4- 6 hours.
Eat stop Eat – this involves fasting for 24 hours, once or twice a week, for example by not eating from dinner one day until dinner the next day.
The 5:2 Diet – With this method you consume only 500–600 calories on two non-consecutive days of the week but eat normally the other 5 days.
Prolonged fasting – 48 hours and longer, generally done under medical supervision. Dr Valter Longo at USC is the generally accepted worldwide expert on this type of fasting and his work is worth reading before you head down this path.
Effect on your body’s cells and hormones
On the cellular and molecular level several things change when you are fasting, for example, your body adjusts hormone levels to make stored body fat more accessible. Ie switching into ketosis
Your cells also initiate important repair processes and change the expression of genes.
Here are some changes that occur in your body when you fast:
Human Growth Hormone – HGH can increase as much as 5x. This has benefits for fat loss and muscle gain, to name a few.
Insulin sensitivity- improved and levels of insulin drop dramatically. Lower insulin levels make stored body fat more accessible.
Cellular repair: When fasting, your cells initiate cellular repair processes. This includes autophagy, where cells digest and remove old and dysfunctional proteins that build up inside cells, this becomes more pronounced the longer the fast.
Gene expression: There are changes in the function of genes related to longevity and protection against disease.
Cell metabolism – Once glycogen stores have been exhausted the body switches to ketosis or very simply put, the utilisation of fat for energy rather than carbohydrates.
Weight loss: Intermittent fasting can be a very powerful tool to help you lose weight and belly fat, without having to consciously restrict calories. In addition to lowering insulin and increasing growth hormone levels, it increases the release of the fat burning hormone norepinephrine. Because of these changes in hormones, short-term fasting may increase your metabolic rate by up to 14%. By helping you eat fewer and burn more calories, intermittent fasting causes weight loss by changing both sides of the calorie equation.
Insulin resistance: Intermittent fasting can reduce insulin resistance lowering blood sugar and fasting insulin levels which logically should protect against type 2 diabetes.
Inflammation: Some studies show reductions in inflammatory markers, a key driver of many chronic diseases.
- Cardiovascular health:Intermittent fasting may reduce “bad” LDL cholesterol, blood triglycerides, inflammatory markers, blood sugar and insulin resistance — all risk factors for heart disease.
- Cancer:Animal studies suggest that intermittent fasting may prevent cancer. This is thought to be true for longer fasts of 48 hours and above, as the majority of cancer causing cells are heavily dependant on glucose metabolism and growth.
- Brain health:Intermittent fasting increases the brain hormone BDNF and may aid the growth of new nerve cells. It may also protect against Alzheimer’s disease.
- Anti-aging:Intermittent fasting can extend lifespan in rats. Studies showed that fasted rats lived up to 80% longer.
The above is all well and good but it must be remembered that much of this research is still in its early stages, mainly done with animal models and for short time frames. New research in this area is released daily and is a very hot area of academic research currently.
Safety and Side Effects
Hunger is obviously the main side effect of intermittent fasting. You may also feel weak and your brain may not perform as well as you’re used to. This is generally temporary, as it can take some time for your body to adapt to the new meal schedule.
If you have a medical condition, you should consult with your doctor before trying intermittent fasting.
This is particularly important if you:
- Have diabetes.
- Have low blood pressure.
- Are underweight.
- Have a history of eating disorders.
- Are a woman who is trying to conceive.
- Are a woman with a history of amenorrhea.
- Are pregnant or breastfeeding.
Intermittent fasting has an excellent overall safety profile. There is nothing dangerous about not eating for a while if you’re healthy and well-nourished overall.
Supplements and Fasting common questions
- What Can I Drink during my Fast?
Generally water, black coffee and tea and other non-caloric beverages are fine. Dailyfx green tea would a particularly good supplement to drink while fasting.
Coffee can also be particularly beneficial during a fast, as it can blunt hunger.
- Can I Work out While Fasted?
Yes, fasted workouts are fine. Some people recommend taking branch chain amino acids (BCAAs) before a fasted workout.
- Will Fasting Cause Muscle Loss?
All weight loss methods can cause muscle loss. That is why it’s important to continue to train and lift weights while keeping your protein intake high. Some studies even show that intermittent fasting causes less muscle loss than regular calorie restriction. Protein supplements containing casein protein which help with hunger cessation may be beneficial when time restricted eating.
You’ve probably already done many intermittent fasts in your life without knowing. If you’ve ever eaten dinner, then slept late and not eaten until lunch the next day, then you’ve probably already fasted for 16+ hours. Some people instinctively eat this way as they don’t feel hungry in the morning. Many people consider the 16/8 method the simplest and most sustainable way of intermittent fasting. There is no need to follow a structured intermittent fasting plan to derive at least some of the benefits. As with any nutritional change experiment with various approaches and find something that works for you and fits your schedule. Once you are used to shorter fasts perhaps then try a longer or prolonged fast 1-2 times a year.
If you would like to do more research in this area Dr Rhonda Patrick is always a good source of information in this area and her pod cast give excellent up to date review of the scientific literature. As mentioned above Dr Valter Longos work on longer fasts and fast mimicking diets may also be of interest.
There are several very good fasting apps available, the App Zero is one of the better ones and an excellent tool to help measure and manage your fasting protocols for you fasting tech junkies.