In a world of endless health advice, making the right moves can be challenging. Diet and nutrition trends come and go, and recommendations often seem conflicting and hard to understand. Amidst the noise and confusion, however, some health trends are backed by the power of science. From fat burning and weight loss to diabetes control and disease reduction, intermittent fasting has been associated with a number of significant health benefits.
Let's look at the dietary methods, biological actions, and real-world benefits of intermittent fasting. When you eat the right foods at the right times, it can have a real positive impact on your health and well-being.
What is intermittent fasting?
Intermittent fasting is also known as intermittent energy restriction, periodic fasting, time-restricted eating, and mealtime schedules. It involves alternating periods of regular eating with short regular periods of zero or limited food consumption. For example, one variant involves alternating five days of regular eating with two days of zero or limited food intake each week. Another variant combines eight hours of regular eating with 16 hours of restricted calorie intake every day.
Fasting has been a regular occurrence throughout history, with always-available food convenience a recent development in human dietary evolution. Along with necessary fasting due to lack of resources, voluntary food avoidance has long existed for health and spiritual reasons. According to some proponents, periodic fasting is a way for modern people to align with some of the ancient factors intrinsic to our cultural and biological coding.
Methods of intermittent fasting
Intermittent fasting is an umbrella term that has been used to describe multiple diet regimes. As you will see, the only thing that distinguishes these methods is the ratio between the time of regular food consumption and the time of zero or restricted food consumption. In order to benefit from intermittent fasting, it's important to find a method that aligns with your underlying physiology and lifestyle needs.
The following methods of periodic fasting are the most popular:
- The 16:8 method - This method is thought by many to be the most sustainable, as it's fairly close to how people eat naturally. The 16:8 ratio was popularised as the Leangains protocol. In most cases, it involves skipping breakfast and restricting your daily eating period to 8 hours later in the day. Early time-restricted feeding is an alternative approach where all meals are taken early in the day. Along with 16:8, other 24-hour cycles such as 20:4 and 18:6 are also possible.
- The 5:2 method - This method stretches out the sequence to seven days instead of one. Standard 5:2 fasting involves regular eating for five days a week and restricted 500 calorie food intake for the other two. While you can avoid food completely over these two days, this is not advised on an ongoing basis. While this method has become popular around the world, long-term motivation can be an issue.
- Alternate-day method - There are multiple ways to alternate regular eating periods with zero or restricted calorie intake periods. The alternate-day method is quite popular, with restricted 500 calorie intake days occurring every second or third day. This is hard for most people, however. Sequenced or irregular 24-hour or one-meal-a-day fasting is another option.
Not all of these diet sequences will be beneficial to all people at all times. However, a number of studies into intermittent fasting have shown promise. While results have been mixed, the majority of research suggests positive weight loss outcomes among other health benefits.
What happens when you fast?
When you eat food, energy enters the body and insulin levels rise. Some of this energy is stored for later use, with insulin the key hormone involved in regulating the storage system. Excess energy is stored in two separate ways — sugar or glucose is stored in the liver or muscles as glycogen, and left-over glucose is stored throughout the body as fat.
Once the storage capacity of the first system is reached, the liver starts to turn excess glucose into fat. This process is called de-novo lipogenesis, which literally means making new fat. The first storage system is easily accessible with limited storage space, and the second is hard to access with almost unlimited space.
Glycogen is readily accessible and highly capable of powering the body for many hours. After this time, the body starts to break down fat in order to make energy. The process of intermittent fasting is based on this key difference, with the "fed" state about storing energy and the "fasting" state about using stored energy. If you don't eat enough food to satisfy your immediate energy requirements, you are making it easier for your body to use its stored energy capacity.
Benefits of intermittent fasting
Intermittent fasting has been widely studied over recent years with mixed results. The US National Institute on Aging said there is insufficient evidence to recommend intermittent fasting. However, a number of other healthcare bodies have provided support. The American Heart Association said intermittent fasting may result in weight loss, reduce insulin resistance, and lower the risk of cardiometabolic diseases.
The following benefits have been highlighted in a range of studies:
Supports fat burning and weight loss
There is some evidence that intermittent fasting leads to weight loss. A number of studies have been carried out, with body mass reduction measured in mice and obese humans of both sexes across multiple ages. Some studies point towards similar but not better results when compared to calorie-restricted diet regimes. However, other studies highlight improved results when intermittent fasting is combined with calorie restriction programs.
Intermittent fasting may be capable of improving metabolic responses by supporting micro-cycles of feast and famine. Not only does this lead to weight loss, but it may also help to counteract metabolic adaptation and weight regain over time. Common 16:8 diets and similar methods can be fairly easy to follow, which is a significant advantage over many restrictive diet regimes.
Lowers blood insulin levels
Insulin helps to control blood sugar levels, which has a direct effect on how energy is used and fat is stored throughout the body. Insulin brings sugar into your fat cells, and most of the time, it keeps it there. We lose weight if we let our insulin levels go down, which is the very basis of intermittent fasting regimes. While low insulin can be very useful in helping people to lose weight, it also offers additional benefits.
One study showed dramatically lower insulin levels, greatly improved insulin sensitivity, and significantly lower blood pressure among a group of obese men with prediabetes who engaged in an early time-restricted feeding program. Due to lower insulin levels and reduced insulin resistance, intermittent fasting can also be an effective non-medicinal treatment option for type 2 diabetes. According to one study, forcing the metabolic switch from glucose-based to stored-fat energy can help to increase stress resistance, which leads to increased longevity and decreased risk of diseases such as cancer and obesity.
Instead of relying on complicated and unrealistic diet regimes, sometimes there's an easier way to live a healthier life. While intermittent fasting is definitely not for everyone, and you should always consult with your doctor before you begin, the rhythm of eating can be a significant factor. Healthy food and exercise will always be the key to good health, and "when" we eat is almost as important as "what" we eat. By syncing our daily food intake with our natural physiology and lifestyle demands, we can benefit from the natural ebbs and flows that define all living things.