There is a long list of amazing changes that occur when we fast and these changes lead to a healthier more joyful existence. People fast for different reasons but I have highlighted some of the major benefits to simply going a day or so without food. To explore “How to fast” see the accompanying article on this website along with other offerings on fasting technique.
1. Metabolic Health Improves – blood sugar, cholesterol and fat burning
- Insulin Sensitivity: Insulin is responsible for taking sugar out of the blood stream and pushing it into the cell for energy. A high carb diet in combination with a sedentary lifestyle promotes insulin resistance which can lead to diabetes. The cell is “resistant” to insulins effect and so you make excess insulin and this is inflammatory and dangerous. Fasting reverses this trend. A study by Jason Fung has shown that fasting alone can reverse diabetes. Better insulin control means you are more easily able to burn fat
- Fat Burning: You have stored sugar in the form of glycogen but that gets used up after 14 to 16 hours of fasting and this is when your body turns to fat burning for energy. The more often you fast and the longer you fast, then the easier and more efficiently you are able to turn on your fat burning mechanism. This aids weight loss and reduces visceral fat, a driver of metabolic disease.
- Cholesterol and Triglycerides: Fasting allows your body to reduce triglycerides levels and keep cholesterol under healthy control
2. Reduced Inflammation
- Autophagy: Fasting forces the cell to use up damaged cellular machinery and clean up the environment inside the cell. So when the fast ends the cell is more efficient at its job. This reduces excess oxidative stress on the cell and reduction in inflammation overall. We can measure reduced levels of “CRP” which is a measure of inflammation.
3. Detoxification
- Antioxidant support: Fasting stimulates the antioxidant pathways we have that produce glutathione. If you have ever fasted and wondered why you have to urinate so much during a fast it's a part of that detox process as the body is clearing junk.
4. Enhanced Brain Function
- Neuroprotection: Fasting raises brain-derived neurotrophic factor (BDNF), which is the repair molecule your body makes to fix damaged nerves. This supports neuronal resilience and reduces your risk for Alzheimers.
- Ketones: Ketones are little units of energy that your body makes when it burns fat. The brain loves ketones and functions very well when they are present. People often comment that their mental focus and general cognition improve while fasting in part due to these ketones.
5. Cellular Repair and Longevity
- Autophagy & Sirtuins: We have already mentioned the benefits of autophagy but fasting also enhances sirtuin activity. Sirtuins are proteins associated with cellular longevity and repair. They are linked to DNA repair and lifespan extension.
- Genes: Fasting activates what are called “longevity genes”. In animal studies in all type, from flys, to mice, dogs and monkeys, we see that fasting can extend life significantly. Some studies show an increase in lifespan by 30%. In humans we don't expect to see 30% but the point is well made that this is good for us.
6. Cardiovascular Benefits
- Blood Pressure: Fasting lowers blood pressure, partly by reducing oxidative stress and improving vascular function. Vascular inflammation is reduced through the effect of ghrelin (hunger hormone) which benefits vascular relaxation.
- Heart Disease Risk: Combining the above mentioned effects of lower cholesterol, inflammation, and weight, fasting cuts overall risk of heart disease.
7. Gut Health
- Microbiome Reset: Fasting gives the gut a break from food digestion, potentially shifting microbial balance toward beneficial species. A 2021 Frontiers in Microbiology study found fasting increased gut diversity in mice.
- Digestive Rest: Reduced workload may heal gut lining, lowering inflammation from “leaky gut.”
Anyone can benefit from the effects of fasting. People with high blood pressure, diabetes and extra weight will trend back toward healthier lab values and may be able to reduce their need for medication over time. Healthy people secure good cellular function and promote longevity while boosting cognition, energy, and living with less inflammation.
There are multiple ways to fast based on duration and cyclical patterns. Start slow with a simple move toward a 16 hour fast. Over time progress to a 24 hour fast as the benefits are worth the effort. Over time you will become curious about the benefits of longer fasts such as 48, 60 or even 72 hour fasts. Beyond a 72 hour fast there is controversy and debate about any further benefit. The muscle loss that occurs with longer fasts makes it challenging to justify the smaller gains. The vast majority of what you want to accomplish can be obtained with the 24 to 36 hour fasting target.
