From water fasting to the 5:2 diet to OMAD, numerous fasting types exist that offer a variety of benefits. As a personal trainer and nutritionist, I have worked with many clients who found intermittent fasting specifically was great for helping them reach their fitness goals.
Everyone has a different experience with fasting and a reason for committing to it, but what are the benefits of fasting? What does the science say? Keep reading to find out!
5 science-backed benefits of fasting
Promotes cellular cleanup
Fasting activates a process called autophagy, where the body clears out damaged cells and regenerates healthier ones. This process supports longevity, immune defense, and cellular repair.
According to an NIH study, “Accumulated evidence suggests that intermittent fasting or calorie restriction can lead to the induction of adaptive autophagy and increase longevity of eukaryotic cells.” This may play a role in delaying aging and preventing diseases.
Improves insulin sensitivity and blood sugar control
One of the most well-studied benefits of fasting is its effect on insulin sensitivity. Fasting helps reduce fasting glucose and insulin levels, especially in overweight or prediabetic individuals. This can help prevent type 2 diabetes and improve overall metabolic health. A 2021 review concluded that time-restricted eating significantly improved insulin sensitivity in both healthy and at-risk individuals.
Supports heart and metabolic health
Fasting has been shown to improve cardiovascular markers, including lower blood pressure, LDL cholesterol, triglycerides, and inflammatory markers. These changes reduce the risk of heart disease and stroke. One scientific review assessed how intermittent fasting could help manage key cardiometabolic risk factors.
Reduces inflammation
Chronic inflammation is associated with numerous diseases, including arthritis, diabetes, and cardiovascular disease. Fasting appears to lower levels of inflammatory markers such as C-reactive protein (CRP). A 2023 study found that fasting reduced systemic inflammation, especially when paired with dietary improvements.
Enhances brain and heart aging resilience
Fasting may protect against age-related decline in the brain and heart. It helps clear out damaged cells in these organs and supports mitochondrial function. A 2024 review highlighted how fasting activates protective pathways that reduce oxidative stress and support long-term cognitive and cardiac health.
What are the different types of fasting?
There are several types of fasting, each with unique structures and benefits. The most popular is intermittent fasting (IF), where you cycle between periods of eating and fasting. Common IF methods include the 16:8 method (fast for 16 hours, eat within an 8-hour window). Time-restricted eating is a subtype of IF that focuses on eating all meals within a set daily window, such as 10 a.m. to 6 p.m.
Intermittent fasting also includes 5:2 fasting (eat normally for five days, restrict calories to about 500–600 on two non-consecutive days) and alternate-day fasting (fast every other day).
Extended fasting lasts longer than 24 hours and can range from 36-hour fasts to multi-day fasts, typically done under medical supervision.
Religious fasting, like during Ramadan or Lent, varies by tradition and includes spiritual and cultural practices alongside dietary restrictions.
Each fasting variation can support different health goals, depending on its duration and the level of consistency.
How do you properly break a fast?
Breaking a fast properly helps your body transition back to eating without discomfort. Start with a small, balanced meal that includes protein, healthy fats, and easily digestible carbohydrates. Avoid high-sugar or highly processed foods, as they can spike your blood sugar and cause bloating. Gentle foods like eggs, bone broth, steamed vegetables, or a smoothie with protein are good choices.
If your fast was longer than 24 hours, reintroduce food slowly and consider smaller portions throughout the day. Always listen to your body and hydrate well as you resume your normal eating habits.
Should anyone avoid practicing fasting?
Even though fasting has its benefits and is quite popular, it isn’t suitable for everyone. People with a history of eating disorders, those who are pregnant or breastfeeding, and individuals with certain medical conditions like diabetes or low blood pressure should avoid fasting unless supervised by a healthcare provider.
Children, teens, and older individuals may also require consistent nutrition that isn’t in line with any fasting variation and should exercise caution if they do decide to fast. Medications that require food can make fasting risky as well. Always consult with a doctor or dietician before starting a fasting routine, especially if you have underlying health issues or are unsure whether fasting is appropriate for your body and lifestyle.
Frequently asked questions
How long is it best to fast for?
The best fasting duration depends on your goals and lifestyle. Common fasting windows range from 12 to 16 hours daily, known as intermittent fasting. Some people try longer fasts of 24 to 48 hours, but these should be done cautiously. Always listen to your body and consult a healthcare professional if you are unsure.
Why is 16 hours the magic number for fasting?
Fasting for 16 hours is popular because it gives the body enough time to shift into fat-burning mode and activate cellular repair processes like autophagy. This window is long enough to offer metabolic benefits while still being manageable for most people, making it an effective and sustainable routine.
Does sleeping count as fasting?
Yes, sleeping does count as fasting. When you’re asleep, you’re not consuming calories, so your body remains in a fasted state. This is why many people include overnight hours in their fasting window, making schedules like 16:8 or 14:10 easier to follow without dramatically changing eating patterns.
