What is intermittent fasting?
First of all, intermittent fasting (IF) is NOT a diet, it’s a term given to an eating pattern that cycles between periods of fasting and eating. It’s a way of scheduling your meals so that you get the most out of them. Intermittent fasting does not say anything about which foods you should eat, but rather when you should eat them!
If we go back to the time of our hunter-gatherer ancestors, they didn’t have supermarkets, refrigerators or food available year-round. Humans have been fasting throughout evolution. AT times fasting was necessary because food was not available and our bodies evolved to be able to function without food for extended periods of time. If anything, fasting from time to time is more ‘natural’ than constantly eating 3-4 (or more) meals per day.
The main reason people try intermittent fasting is to shed body fat. Intermittent fasting is known to be one of the simplest strategies for taking the ‘bad weight’ off whilst keeping the ‘good weight’ on. In other words, it’s a good way to keep muscle mass on while getting lean and losing body fat.
How does it work?
To understand how intermittent fasting leads to fat loss, it is crucial to understand the difference between the fed state and the fasted state.
Fed State: Your body is in the fed state when it is digesting and absorbing food. Typically, the fed state starts when you begin eating and lasts for three to five hours as your body digests and absorbs the food you just ate. When you are in the fed state, it’s very hard for your body to burn fat because your insulin levels are high.
Fasted State: After the fed state timespan, your body goes into what is known as the post-absorptive state, i.e. your body isn’t processing a meal. This lasts 8 – 12 hours after your last meal, which is when you enter the fasted state. It is much easier for your body to burn fat in the fasted state because your insulin levels are low. When you’re in the fasted state, your body can burn fat that has been inaccessible during the fed state.
Because we don’t enter the fasted state until 12 hours after our last meal, it is very rare that our bodies are in this fat burning state. This is one of the key reasons why many people who start intermittent fasting will lose fat without changing what they eat, how much they eat or how often they exercise. Fasting puts your body in a fat burning state that you rarely make it do during a normal eating schedule (3-4 meals or more per day).
Intermittent fasting has many benefits…
- Intermittent fasting changes the function of cells, genes and hormones.
When you don’t eat for a while, several things happen in your body.
Your body initiates important cellular repair processes and changes hormone levels to make stored body fat more accessible.
- Insulin levels: blood levels of insulin drop significantly, which facilitates fat burning.
- Human growth hormone: the blood levels of growth hormone may increase as much as 5-fold. Higher levels of this hormone facilitate fat burning and muscle gain.
- Cellular repair: the body induces important cellular repair processes such as removing waste material from cells.
- Gene expression: There are beneficial changes in several genes and molecules related to longevity and protection against disease.
- Intermittent fasting can help you lose weight and belly fat
Many of those who try intermittent fasting are doing it to lose weight.
Generally speaking, intermittent fasting will make you eat fewer meals. Unless if you compensate by eating much more during the other meals, you will end up consuming fewer calories.
Additionally, as previously mentioned, intermittent fasting enhances hormone function to facilitate weight loss.
Lower insulin levels, higher growth hormone levels and increased amounts of norepinephrine all increase the breakdown of body fat and facilitate its use for energy. For this reason, short-term fasting actually increases your metabolic rate by 3.6-14%, helping burn even more calories.
According to a 2016 review of the scientific literature, intermittent fasting can cause weight loss of 3-8% over 3-24 weeks! This was also paired with a loss of 4-7% from their weight circumference, which indicates that they lost belly fat which is the harmful fat in the abdominal cavity that causes diseases.
An additional study also showed that intermittent fasting caused less muscle loss than continuous calorie restriction.
- Intermittent fasting can reduce insulin resistance, lowering your risk of type 2 diabetes.
In recent decades, type 2 diabetes has become incredibly common in recent decades. Its main feature is high blood sugar levels in the context of insulin resistance. Anything that reduces insulin resistance should help lower blood sugar levels and protect against type 2 diabetes.
Intermittent fasting has been shown to have major benefits for insulin resistance and lead to an impressive reduction in blood sugar levels. In human studies on intermittent fasting, fasting blood sugar has been reduced by 3-6%, while fasting insulin has been reduced by 20-31%.
- Intermittent fasting may be beneficial for heart health
Heart disease is currently the world’s biggest killer. It is known that various ‘risk factors’ are associated with either an increased or decreased risk of heart disease.
Intermittent fasting has been shown to improve numerous different risk factors, including blood pressure, total and LDL cholesterol, inflammatory markers and blood sugar levels.
Risk factors to consider…
As with any change to your diet, you should consider the risk factors before choosing to begin any diet programme.
Potential side effects for anyone who fasts include:
- Low energy
- Trouble concentrating
If you decide to follow an intermittent fasting diet, you should drink lots of water. This will help with the loss of hydration you may encounter when eating less food.
Is intermittent fasting for you?
With the heightened media attention surrounding intermittent fasting, more evidence is needed to support this type of diet. Though some studies do show that intermittent fasting results in short-term benefits like weight loss, there are few long-term studies.