Fasting is one of the
oldest healing traditions in human history. It was practiced by almost every
culture or religion and has many proven health benefits. Fasting is defined as the
absence of food for a longer period of time. It can be involuntary, which was
the case when our ancestors were hunters and gatherers and couldn’t eat every day. It can also be voluntary
by intentionally withholding food for health, spiritual or other reasons. Fasting
is rather a natural eating pattern, to which our bodies adapted over thousands
of years. In fact, our ancestors could withstand longer periods without food
and still be able to pursue high intensity physical activities like hunting and
running from danger. Evolutionary theory would therefore suggest that our
bodies are not meant to eat 3-4 meals a day, because our bodies got adapted over
millions of years to longer fasting periods.
What is Intermittent Fasting?
Intermittent fasting (IF) is less of a diet, but rather an
eating pattern, where you control the time when you eat and the time when you
fast. IF doesn’t define what food to eat but provides different methods to simulate
short or longer fasting periods. It has caught a lot of attention recently,
because some scientific studies indicate significant health benefits and IF eating patterns are easier to execute
than specific diets.
Affects the Body
Fasting is a critical
parameter which affects our metabolism and triggers many processes on a cellular
and molecular level. From a high-level perspective, fasting induces a katabolic
state in cells, which triggers hormones, repair processes and also changes the
expression of genes.
Here are the main
processes we observe during fasting – it is very likely that
these processes and mechanisms are interrelated:
- Increase of human growth hormone
(HGH) production: During a
fasting period, the production of HGH increases up to 400% and these increased
levels lead to muscle growth and fat loss.
- Reduction of insulin response: Due to the reduction or lack of glucose in the
blood during a fast, the levels of insulin decease which improves insulin
sensitivity and reduces cravings. Due to reduced insulin, the fat storage
process is restricted as well, which can result in weight loss.
- Autophagy (cellular “recycling”): Autophagy is a natural destructive mechanism of
the cell that allows degradation and recycling of cellular components. When
fasting puts the cells in a katabolic
state, they induce autophagy, where they recycle re-usable proteins
and remove disfunctional or damaged cell components (find a more detailed
- Production of ketones: After the glycogen levels are depleted during
a fast, the liver will start to process stored fat and produce ketones. This
can result in a mild state of ketosis with an increased ketone blood
concentration (>0.5 mmol/l).
- Reduction of inflammation and oxidative stress: Several studies point out, that inflammation
levels are being reduced significantly during a fast. The reason is not well
understood. One hypothesis states that because of a reaction of the immune
system resulting from a damaged gut wall or leaky gut, body inflammation levels
are increased significantly. Fasting can help to improve your gut microbiome
and even help to heal a leaky gut and therefore reduce inflammation.
Health Benefits of IF
Based on the processes
described above, IF has several
- Improved mental clarity and increased energy
- Increased fat burning and weight loss
- Reduced risk of Type 2 Diabetes
- Improved heart health, lowered blood cholesterol and risk of
- Anti-aging potential and longer life
- Cancer reversal and prevention
- Improved brain health and lowered risk of neurodegenerative diseases
- Healing of gut
- Decreased hunger
- Strengthening of immune system
- Improved skin
These are the most popular methods for IF that you can try:
The 16:8 Method (Leangains protocol):
With this method, you can
eat during a period of 8 hours per day and restrict food during the remaining
16 hours. Most people find it easiest to skip breakfast and eat 2-3 meals
between noon and 8pm. The 16:8 method doesn’t
restrict any calories and depending on your weight target, you can eat the same
number of calories as usual, just within a restricted period.
This method involves a
24 hour fast once or twice a week. During the fasting period, you should drink
calorie-free beverages like water or unsweetened tea to stay hydrated and you
should supplement with sea salt and other electrolytes to avoid headaches or
fatigue. You can break the fast with a large meal or just with a small snack,
whatever makes you feel better. If you want to boost weight-loss and improve
your body composition, you can work out during the fasting period.
1-Meal-A-Day (Warrior Diet):
The 1-meal-a-day diet
is very popular due to its effectiveness, but difficult to execute for most
people, due to the 20 hour+ fasting periods. The meal is mostly consumed in the
late afternoon or evening, because you will fall asleep easier on a full
stomach. You do not have to restrict calories on this diet, but because it is
difficult to eat 1 meal of 2,000-2,500 kcal at once, you usually restrict
calories by 20-25% with this method. Due to the long and regular (daily)
fasting periods and mild calorie restriction, the health benefits described above
are most prominent in this method.
We do not consider the
5:2 Method a real intermittent fasting method, because it’s more a calorie restriction method without a clear eating pattern. With
the 5:2 Method, you eat regularly during 5 days per week and on 2 non-consecutive
days you restrict your calories to 500- 700 kcal.
Side Effects and Risks of IF
- Cravings - When you start your IF
routine, your body expects food at the times you regularly had your meals in
the past. So, when you omit these meals the body will react to it with hunger
and cravings. These cravings will vanish after the body is adjusted to the new
eating pattern after about 2-3 weeks.
- Headaches - Due to the reduction of stored water in your body, you also flush-out
important minerals, such as sodium, potassium, magnesium and calcium. Make sure
to drink sufficient water and add a tablespoon of sea salt. You can also take supplements to counter
- Low Energy - Having low energy can have several reasons. One may be the lack of
minerals mentioned above. Another reason could be that the body is not well
adapted to burning fat as fuel. Therefore, we recommend a 3-week keto-adaption program before you start IF to make sure that your body can run
efficiently on fats.
- Irritability - Everyone knows that if people are hungry, they are usually in a very bad
mood and short tempered. If keto adapted, the body will cycle into mild ketosis
(>0.5 mmol/l) during the fasting period and with increasing blood ketone concentration
the body starts to regulate hunger-related hormones, which suppress the feeling
of hunger and reduce irritability. This is just another reason to wait until
you are fully keto-adapted before you begin a IF regimen.
- Overeating - When people start IF, a
powerful psychological process takes place, where you feel that something is
being taken away from you. This feeling
is regularly overcompensated with overeating during the eating periods. This is something to be aware of and monitor
to the best of your ability.
- Heartburn, Bloating & Constipation - Overeating and the adaption of the metabolism can cause digestive issues in the short term. To avoid this, you should eat whole and fresh foods and omit processed foods as a general rule.
If you have any
medical conditions, you should consult with your doctor before trying IF. Following conditions or situations
require particular caution:
- Problems with blood sugar regulation
- Low blood pressure
- Take medications
- If you are underweight
- History of eating disorders
- If you are trying to conceive
- If you are pregnant or breastfeeding
Overall IF is considered to be a very safe eating pattern and
there is nothing dangerous about IF,
if you eat healthy.