Intermittent fasting has become somewhat of a buzzword in recent years but isn’t just a modern trend. According to some experts, it’s a return to how humans are naturally designed to eat–and it can be a powerful tool to support your overall well-being.
Read on for a deep dive into the most significant intermittent fasting benefits and side effects–plus practical tips to get you started.
Does intermittent fasting work?
Intermittent fasting offers some impressive health benefits, impacting nearly every system in the body. The primary positive effects are:
Immune system regulation
When fasting, your body redirects its energy from digesting food to conserving resources and resisting stress. This shift optimizes immune system functions, allowing your body to fight infection and inflammation promptly.
Studies show that fasting increases antibody responses to bacterial infections like Salmonella and may even reduce symptoms of autoimmune diseases like multiple sclerosis (MS) and asthma.
Other research suggests that fasting helps balance the gut microbiome (the population of trillions of microbes living in the digestive tract), another essential contributor to immunity.
Genetic and cellular repair
Fasting activates your body’s cellular repair mechanisms–notably one called autophagy.
Autophagy is a process during which cells eliminate damaged components (such as mitochondria) to promote genetic stability and longevity. This enables cells to recycle and repurpose these elements for energy and is key for slowing down both the aging process and the progression of disease.
Fasting also helps lower insulin levels while increasing glucagon, a hormone the pancreas makes to regulate blood sugar levels. This hormonal balance further supports autophagy.
Some studies show autophagy accelerates as soon as 12 hours into fasting, although others suggest it starts at 24 hours and peaks around 48 hours. Depending on how long you fast, you may experience some or all of these helpful cellular repair benefits.
Diminished insulin resistance
As just mentioned, intermittent fasting balances insulin and glucagon levels, regulating blood sugar and stabilizing hormonal fluctuations. In these ways, it’s fantastic for metabolic health and can help lower your risk of developing type 2 diabetes.
Research also suggests that intermittent fasting improves metabolic markers such as lipid profiles and glycemic control, particularly in those already diagnosed with type 2 diabetes and obesity.
Healthy weight loss
Fasting can be extremely helpful with weight loss and maintenance, thereby combating obesity.
It naturally reduces calorie intake, as long as you don’t over-fuel during eating windows. It promotes fat loss without sacrificing muscle mass, especially when complemented by weight training.
A comprehensive review of 27 studies found that intermittent fasting leads to reductions in weight ranging from 0.8% to 13% of baseline body weight, regardless of total caloric intake.
Reduced oxidative stress and inflammation
Intermittent fasting can help combat inflammation and oxidative stress. These are two key factors associated with many chronic conditions–from inflammatory bowel disease to rheumatoid arthritis to psoriasis.
Evidence shows intermittent fasting can lower levels of certain substances in the body, known as inflammatory markers (TNF-α, IL-6, and isoprostanes), which experts have linked to ongoing health problems and increased stress on cells.
This may be one mechanism behind fasting’s ability to alleviate pain and improve the quality of life for those suffering from chronic, inflammatory conditions.
Heart health
Intermittent fasting reduces inflammation–a key contributor to heart disease–and promotes overall cardiovascular wellness. It does this by improving other factors of arterial health, such as lipid and triglyceride levels.
It can also decrease cholesterol production, which is crucial since high cholesterol is a major risk factor for atherosclerosis (thickening or hardening of the arteries due to plaque buildup). Studies have highlighted significant reductions in total cholesterol and LDL (“bad”) cholesterol with intermittent fasting.
Furthermore, it can benefit blood pressure–another critical factor in heart disease risk. One study found that just five weeks of time-restricted eating could lower systolic and diastolic blood pressure by about 10-11 points.
That’s comparable to the effects of some blood pressure medications.
Cancer prevention
While research is ongoing, some studies suggest that intermittent fasting could lower your risk of certain cancers, such as breast cancer. That’s because it improves metabolic factors like insulin sensitivity and glucose control.
A key intermittent fasting benefit is accelerated autophagy, as discussed above. Because this process helps clear away damaged cells, it can inhibit the growth of cancer cells while reducing inflammation.
This includes lowering insulin-like growth factor (IGF-1) levels, which is associated with the development of certain cancers like that of the breast and prostate.
Emerging evidence also suggests that intermittent fasting could improve the effectiveness and tolerability of anticancer medicines, offering new ways to support those undergoing cancer treatment.
Improved cognitive health
Fasting can also boost your brain health. Along with reducing inflammation and oxidative stress, it promotes the production of neurotrophic factors (proteins that support neuron growth and protection).
This improves cognitive function and helps prevent the decline associated with aging and neurodegenerative diseases like Alzheimer’s and Parkinson’s. Studies suggest intermittent fasting specifically increases levels of the most abundant and well-studied neurotrophic factor, brain-derived neurotrophic factor (BDNF), which plays a vital role in:
- Brain function
- Neuronal development
- Neuroplasticity (the ability of neurons to adapt and change)
Greater longevity
Through triggering autophagy and optimizing other physiological functions, intermittent fasting may help you live longer. A 2021 study found that combining intermittent fasting with other healthy lifestyle habits reduced participants’ biological age by 3.23 years.
Is fasting safe?
Intermittent fasting is safe for many people, but it’s not for everyone. Skipping meals may not be the best way to manage your weight if you’re pregnant or breast-feeding. If you have kidney stones, gastroesophageal reflux, diabetes or other medical problems, talk with your doctor before starting intermittent fasting.
How often is fasting healthy?
The frequency of healthy fasting may largely depend on your:
- Goals
- Personal tolerance
- Health status and underlying medical conditions
- Other lifestyle factors
Studies suggest more restrictive strategies like the 5:2 diet could offer additional benefits–particularly for managing conditions like diabetes and cancer. However, these methods can be intense for beginners and may be more difficult to sustain.
So, discuss intermittent fasting with your healthcare provider, and start slowly. You can experiment with one or more of the following strategies.
Time-restricted eating
- 16/8 Method: Fast for 16 hours and eat within an 8-hour window.
- 14/10 Method: Fast for 14 hours and eat within a 10-hour window.
Twice-a-week fasting (The 5:2 diet)
Fast for 24 hours on two non-consecutive days of the week, eating normally the other five days. Alternatively, you can fast one day per week.
Alternate-day fasting
Alternate between no food consumption or significant calorie reduction and days of normal eating.
One meal per day
Consume one large, nutrient-dense meal daily, fasting for the remaining 23 hours.
Partial fasting
Exclude certain food groups or beverages, like sugar or processed foods, for specific periods.
A practical guide to starting intermittent fasting
How to start
Intermittent fasting can seem daunting, but you can take gradual steps to make it easier.
Choose a fasting plan that aligns with your health goals, eating habits, and lifestyle. For many, starting with a mild version of time-restricted eating, such as a 12-hour fasting window, helps ease the transition.
What to expect: Intermittent fasting side effects
When starting intermittent fasting, some people experience side effects such as:
- Hunger pangs and cravings
- Headaches
- Irritability or mood changes
- Fatigue
- Weakness
- Constipation
- Sleep disturbances
- Dizziness
- Lightheadedness
These side effects typically subside after the initial adjustment period, which can take a few days to a few weeks.
Use the following tips to manage them and get to feeling your best faster.
Tips for intermittent fasting success
- Stay hydrated. Drink plenty of water–especially during fasting periods. It’s vital for your health and can remedy headaches, fatigue, and constipation. Herbal tea can also be beneficial.
- Eat balanced meals. When you eat, prioritize nutrient-rich foods that include protein, healthy fats, and fiber. These nutrients will sustain you through fasting and help manage fatigue, constipation, dizziness, and irritability.
- Be consistent. Stick closely to your fasting schedule and maintain similar eating times each day.
- Monitor your progress. Track your fasting hours, feelings, and any changes in body weight or energy levels in a journal so you can adjust your approach as needed.
- Consult your doctor. Intermittent fasting may not be suitable for everyone–especially those with certain health conditions or on specific medications. Talk to your healthcare provider before beginning.
Intermittent fasting has numerous health benefits and, for most people, few side effects. Start gradually by eating an early dinner and pushing back your breakfast time to ease into the practice.
It won’t be long before you enjoy better immune function, metabolic health, and vitality. With a mindful, well-informed approach, this habit can be a powerful part of your wellness journey.
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