Intermittent fasting is one of the most popular nutritional systems in the world, and it may help with weight loss, improve health, improve cognitive function, heart health, and digestion.
You’ve probably practiced intermittent fasting many times in your life. If you ate dinner before, then slept late and didn’t eat until lunch the next day, you have already fasted for more than 16 hours. Some people eat this way intuitively because they simply don’t feel hungry in the morning.
What is intermittent fasting?
Intermittent fasting is an eating pattern that alternates between periods of fasting and eating.
Intermittent fasting does not specify which foods to eat, but rather when to eat them. This means that it is not actually a diet – but rather a more precise dietary pattern.
Popular intermittent fasting methods involve fasting for 16 hours with an 8-hour eating window. Some people fast for 24 hours twice a week.
You can practice intermittent fasting in several different ways, although all involve dividing the day or week into eating and fasting periods.
During fasting periods, you will not eat anything. You can usually drink calorie-free beverages such as water, herbal tea, and black coffee.
Intermittent fasting methods
These are the most common methods:
16/8 method: Also called the Leangains protocol, it involves an 8-hour eating period and a 16-hour fasting period. Some people do this by skipping breakfast, but you can also do the opposite and skip dinner or eat early.
Eat, stop, then eat: This method involves fasting for 24 hours once or twice a week. Because this is a slightly more advanced version of fasting, you should only try it if you are very comfortable with the practice.
Diet 5:2: In this method, you consume only 500-600 calories on two non-consecutive days of the week but eat as usual on the other five days.
For many people, shortening the eating window also reduces the number of calories they eat daily. Over time, this can contribute to weight loss.
Many people consider the 16/8 method to be the simplest and most sustainable form of intermittent fasting – you may want to try this practice first.
If you find it easy and feel comfortable while fasting, perhaps you can try moving on to more advanced fasting methods. Another approach is to fast whenever appropriate. Simply skip meals from time to time when you are not hungry or do not have time to cook.
There is no need to follow a structured intermittent fasting plan to get at least some benefits. Try different methods and find something you enjoy that fits your schedule
How does intermittent fasting affect your cells and hormones?
When you fast, several things happen in your body at the cellular and molecular level.
First, human growth hormone (HGH) levels rise and insulin levels fall. Your body’s cells also change gene expression and initiate important cellular repair processes.
Here are some of the changes that happen in your body when you fast:
- Human Growth Hormone: Your human growth hormone levels increase. This can help with both fat loss and muscle growth.
- Insulin: When fasting, insulin sensitivity improves and insulin levels decrease. Low insulin levels make stored body fat more accessible.
- Cell repair: When you fast, your cells begin cell repair processes. This includes autophagy, which means cells digest and remove old, non-functional proteins that build up inside them.
- Gene expression: Fasting can cause changes in the function of genes related to longevity and disease prevention.
Can intermittent fasting support weight loss?
Weight loss is the most common reason people try intermittent fasting. By reducing the amount of time you can eat, you will likely consume fewer calories without even realizing it.
Additionally, intermittent fasting can affect hormone levels and aid in weight loss, according to a report in Healthline.
In addition to lowering insulin and increasing human growth hormone levels, intermittent fasting increases the secretion of the fat-burning hormone norepinephrine (norepinephrine). Because of these changes, short-term fasting may temporarily increase your metabolic rate.
According to research, intermittent fasting can be a powerful weight loss tool when done safely. A 2020 systematic review of studies in overweight and obese people showed weight loss rates ranging from 0.8% to 13% of participants’ starting weights. However, most of these studies were small and conducted over a short period of time.
Keep in mind that the main reason intermittent fasting helps with weight loss is that it makes it easier to eat fewer calories overall. If you eat large amounts of food during your binge eating periods, you may not lose any weight at all.
Health benefits of intermittent fasting
Studies have shown that intermittent fasting may have benefits for weight management and overall health. However, keep in mind that much of the current research involves small, short-term studies. This means that researchers need more information to understand how intermittent fasting can help with sustainable, healthy weight loss.
Here are the main health benefits of intermittent fasting:
- Weight loss: Intermittent fasting can help you lose weight and body fat without having to consciously restrict calories.
- Insulin resistance: Intermittent fasting can reduce insulin resistance, which occurs when your body does not respond properly to insulin, leading to increased blood sugar levels. Controlling your blood sugar can protect you from developing type 2 diabetes.
- Inflammation: Some studies show a decrease in markers of inflammation, a major factor in many chronic diseases.
- Brain health: Studies conducted on mice have shown that fasting increases the brain hormone BDNF and may help in the growth of new nerve cells.
Who should be careful or avoid intermittent fasting?
Fasting is definitely not for everyone. If you are underweight or have a history of eating disorders, you should not fast without talking to your doctor first.
Should women fast?
Some evidence suggests that intermittent fasting may not be beneficial for women.
There are a number of anecdotal reports of females whose periods stopped when they started intermittent fasting and returned to normal when they resumed their previous eating pattern. This is likely because fasting can disrupt female hormones, affecting the menstrual cycle and overall health.
However, intermittent fasting may be a useful tool for some women. Research has shown that it can help treat androgen excess in women with polycystic ovary syndrome (PCOS), which may affect ovulation and fertility.
According to a 2023 research review, studies have shown that for average-weight females, intermittent fasting can harm reproductive health and performance if it causes insufficient calorie intake, especially in female athletes.
Experts suggest that women be careful when following intermittent fasting.
If you’re considering intermittent fasting, it’s best to speak with a doctor or nutritionist to determine if it’s right for you.
Safety considerations and side effects of intermittent fasting
Hunger is the main side effect of intermittent fasting. You may also feel weak, and your brain may not work as efficiently as it used to. This may only be temporary, as your body may take some time to adapt to the new meal schedule.
If you have a medical condition, you should consult your doctor before trying intermittent fasting.
This is especially important if you:
- He has diabetes
- You have problems regulating blood sugar
- You have low blood pressure
- You are taking medications
- You are underweight
- You have a history of eating disorders
- You are trying to get pregnant
- You have a history of menopause
- Pregnant or breastfeeding
Is it possible to drink fluids while fasting?
Yes. Water, coffee, tea and other non-calorie drinks are fine. Coffee can be especially beneficial during fasting because it can reduce appetite.
Isn’t skipping breakfast unhealthy?
No, skipping breakfast will not harm your health. If you make sure to eat healthy for the rest of the day, the practice is completely healthy.
Can I take nutritional supplements while fasting?
Yes. However, keep in mind that some supplements, such as fat-soluble vitamins, may work best when taken with meals containing a fat source. Many supplements can also cause stomach upset when taken without food.
Is it possible to exercise while fasting?
Yes, exercising while fasting is acceptable. Expect to feel more tired and weak than usual, so relax and listen to your body.
Does fasting cause muscle loss?
All weight loss methods may cause muscle loss. Make sure to eat plenty of protein and do muscle-strengthening exercises, such as lifting weights.