Unlike many other diets that restricts the type of food, macros, and nutrient composition of your diet, intermittent fasting focuses on the time when you're eating and the periods of fasting between meals. Research on intermittent fasting has shown spectacular benefits on the body and brain. Though, you may be wondering, "is it safe?" "what are the benefits?".
There are two main types of intermittent fasting: daily 16-hour fasts with 8 hours of 'eating time', or fasting for 24 hours, twice per week. Humans can function for more long periods without food, as our ancestors who had no supermarkets and refrigerators often relied on hunting for their next meal. Some religions fast for spiritual reasons, including in Islam, Christianity, Judaism and Buddhism. The types of fasting is broken down below:
The 16/8 method: This is a daily routine that involves restricting your daily eating period to 8 hours, such as 10am-6p.m. Then you fast for 16 hours in between. This is the most popular routine due to its simplicity and easiest to commit to in the long-run.
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: In this method, you are restricted in to consume only 500–600 calories on two nonconsecutive days of the week (calorie-deficit), but eat normally the other 5 days.
During periods of 'no-eating', you can still consume liquids such water and zero-calorie beverages such as black coffee and tea. When you are eating, you should be mindful that only by restricting the time you eat will not directly help you achieve a healthier body system if you constantly consume junk food or overeat during these periods.
How Intermittent Fasting Affects Your Hormones:
During periods of fasting, your body will have no food and nutrient from digestion to fuel your metabolic functions, so your body adjusts hormone levels to make stored body fat more accessible. The hormonal changes are summarized below:
1. Increase in human growth hormone (HGH)
This hormone is suppressed when feeding, so fasting reverses this action and acts as a stimulus to HGH secretion. Therefore, the HGH hormone increases as much as 5-fold during fasting, which is responsible for many benefits such as fat loss, muscle gain (Blackman, Marc R et al.).
Insulin is a hormone that regulates the blood glucose (sugar) levels in your body. When you are fasting, there isn't much glucose in the bloodstream because you are not consuming any glucose from foods. Insulin helps to retrieve glycogen, which is stored in the liver, and breaks it down to increase blood glucose. By practicing fasting, insulin sensitivity improves, making it easier for your body to use glucose for energy to perform bodily functions, rather than storing it in your fat cells (Heilbronn, Leonie K et al.).
3. Enhances cellular repair:
When fasting, it increases cellular stress resistance and defence. Here, stress is actually a good thing because it improves the resistance of cells to variety of other possible stressors such as chronic injury. It also initiates a process called "autophagy", where cells digest and remove old and dysfunctional proteins that build up inside cells to prevent accumulation of toxins within the body.
4. Gene expression:
Many studies have shown that there are changes in the function of genes related to longevity and protection against disease
Reasons for Intermittent Fasting
This is the goal for many people seeking diets. The intermittent fasting is especially effective for weight loss because it forces you to eat less meals throughout the day, and even possibly consume lower caloric intake because you are eating most of your meals in a shorter time frame. This makes you less prone to being hungry in between the first and second meal, which may influence you to eat less. When you eat less, you enter a state of calorie deficiency, where your daily calorie-intake is lower than calorie-expenditure, thus helping to loss weight.
It also increases the release of the fat-burning hormone norepinephrine. This is a stress hormone that enhances the overall rate of fat loss by stimulating the release of fatty acids from fat cells into the bloodstream for burning as fuel. This increases your metabolic rate, which automatically makes you burn more calories. Research also shows that the fat loss is mostly from the harmful belly fat rather than muscle loss, which makes it better than other calorie-restrictive diets that tugs away at muscle mass.
2. Brain Health:
Intermittent fasting increases the brain hormone BDNF and may aid the growth of new nerve cells. The hormone BDNF provide instructions for making a protein found in the brain and spinal cord called brain-derived neurotrophic factor. This protein plays a critical role in promoting the growth, maturation, survival, and maintenance of nerve cells (neurons) in the brain, helping to protect against Alzheimer’s disease.
Intermittent fasting can extend lifespan in rats. Studies showed that fasted rats lived 36–83% longer. This may be due to a variety of factors, such as improved brain health and maintenance of nerve cells (mentioned above), healthier weight for the body to efficiently and effectively carry out metabolic functions, etc.
Though, you should note that many of these benefits are still in their early stages of development, and may not always be the outcome for every individual due to differences in environmental factors, age, lifestyle and family medical histories.
Who should avoid it?
As intermittent fasting is restrictive of when you're eating, pregnant women or those experiencing rapid phrases of growth, such as children and teenagers, should not attempt to try intermittent fasting. Pregnant mothers and growing teenagers have a high metabolic rate as their body is changing and growing, so they will need to fuel their body with food when needed.
Intermittent fasting, like many other diets, is not a magic diet that will work for everyone. It can fit perfectly for those who instinctively does not feel hungry in the morning, but not for others who require lots of food as fuel to power through their jobs. When it comes to picking a diet, find the style that works best for your schedule in the long-run, whether that being sleeping well, staying hydrated, and eating whole-foods. Life-long habits is what will help you become a healthier individual, and stay sharp for the years to come.