Intermittent fasting has become one of the most popular nutrition strategies in recent years and for good reason. Unlike many diets that focus on what you eat, intermittent fasting focuses primarily on when you eat. Research suggests that, for many people, it may support weight management, improve metabolic health & promote healthy aging when practiced safely.
That said, intermittent fasting isn't right for everyone. As a licensed Naturopathic Doctor and primary care healthcare provider with nearly 20 years of clinical experience, I've seen some patients thrive with intermittent fasting while others experience fatigue, headaches, or hormonal disturbances because the approach wasn't appropriate for their body or lifestyle.
Through my education as a Naturopathic Doctor and years of clinical practice, I have learned that successful nutrition plans are never one-size-fits-all. We need to understand patients deeply to provide truly holistic care, considering their age, medical history, medications, work schedule, activity level, sleep & personal goals before recommending any fasting diet.
What is intermittent fasting?
One of the most common questions patients ask is, "What is intermittent fasting?"
Intermittent fasting is an eating pattern that alternates between periods of eating and periods of fasting. Rather than restricting specific foods, it limits the time window during which calories are consumed. During fasting periods, the body gradually shifts from using recently consumed carbohydrates for energy toward utilizing stored energy reserves. Intermittent fasting is not a specific diet—it is an eating schedule that can be combined with many healthy dietary patterns.
How does fasting work?
Patients often ask, "How does fasting work?"
After eating, your body primarily uses glucose from food as its main energy source. As several hours pass without food, insulin levels gradually decline, allowing stored glycogen in the liver to be used for energy. Once glycogen stores begin to decrease, the body increasingly shifts toward burning stored fat. During longer fasts, ketone production also increases, providing an alternative fuel source for the brain and other tissues. In theory, we learn about these metabolic pathways in textbooks, but in clinical practice I have observed that patients experience them very differently. Some adapt within a week or two, while others require a slower transition before feeling comfortable fasting.
Research suggests that intermittent fasting benefits may include improved insulin sensitivity, weight management, cardiovascular health & metabolic function when combined with a balanced, nutrient-rich diet.
Stages of fasting by hour
Although everyone's metabolism is different, the body's physiology generally progresses through predictable stages of fasting by hour.
|
Hours Since Last Meal |
What Is Happening? |
|---|---|
|
0–4 hours |
Digestion and absorption of nutrients |
|
4–12 hours |
Blood sugar and insulin gradually decline |
|
12–16 hours |
Increased use of stored glycogen and beginning of greater fat utilization |
|
16–24 hours |
Fat burning becomes more prominent and ketone production gradually increases |
|
Beyond 24 hours |
Greater metabolic adaptations occur and should only be undertaken with appropriate medical guidance for most individuals |
These are general physiological stages and should not be interpreted as strict timelines for every person.
Different types of fasting
There are several different types of fasting, each with its own advantages.
Common approaches include:
Time-restricted eating
The most popular form of intermittent fasting.
Examples include:
- 12:12 schedule
- 14:10 schedule
- 16 hours fasting (16:8 schedule)
Alternate-day fasting
People alternate between normal eating days and days of significant calorie restriction.
5:2 fasting
Five days of normal eating and two non-consecutive days with substantially reduced calorie intake.
Extended fasting
Fasts lasting longer than 24 hours. These should only be undertaken with appropriate medical supervision in selected individuals.
The 16:8 intermittent fasting schedule
The most widely studied intermittent fasting schedule is the 16:8 approach.
With this method:
- Fast for approximately 16 hours
- Eat during an 8-hour window
For example:
- First meal: Noon
- Final meal: 8:00 PM
During the fasting period, water and other calorie-free beverages are generally permitted.
For many patients, this is the easiest intermittent fasting plan to incorporate into everyday life because it often involves simply delaying breakfast.
Intermittent fasting times
There is no single "best" set of intermittent fasting times.
Examples include:
- 8:00 AM – 4:00 PM
- 10:00 AM – 6:00 PM
- Noon – 8:00 PM
If your main goal is weight management, this related guide on Intermittent fasting windows for belly fat loss explains how different eating windows may fit into a broader nutrition and lifestyle plan.
In my opinion, the best schedule is one that is realistic, sustainable & fits naturally with a person's work, family, sleep & exercise routine.
Intermittent fasting benefits
Research continues to evolve, but current evidence suggests several potential intermittent fasting benefits for appropriate individuals.
These may include:
Weight management: Reducing the eating window may naturally decrease overall calorie intake for some people while improving awareness of hunger and satiety.
Improved insulin sensitivity: Some studies suggest intermittent fasting may improve the body's response to insulin, particularly when combined with a nutritious diet and regular physical activity.
Cardiovascular health: Research has demonstrated modest improvements in several cardiovascular risk factors, including:
- Blood pressure
- Triglycerides
- Insulin resistance
- Body weight
Reduced inflammation: Some evidence suggests fasting may help reduce certain inflammatory markers, although this remains an active area of research.
Simplicity: Many patients appreciate that intermittent fasting simplifies meal planning because fewer meals need to be prepared each day.
Intermittent fasting results
Patients often ask about expected intermittent fasting results. Results vary considerably.
Potential outcomes may include:
- Gradual weight loss
- Improved energy
- Better blood sugar regulation
- Improved metabolic health
- Reduced late-night snacking
However, these benefits depend largely on the quality of food consumed during the eating window. Intermittent fasting is not permission to eat unlimited amounts of highly processed food.
Is intermittent fasting safe?
One of the most important questions is, "Is intermittent fasting safe?" For many healthy adults, intermittent fasting can be safe when performed appropriately. However, it is not appropriate for everyone.
It should generally be avoided or carefully supervised in individuals who are:
- Pregnant
- Breastfeeding
- Underweight
- Children or adolescents who are still growing
- Living with eating disorders or a history of disordered eating
- Taking medications that significantly affect blood sugar unless supervised by their healthcare provider
Not all patients are equal based on age and gender because nutritional needs, hormone balance, medications & medical conditions vary considerably. When it comes to seniors, maintaining muscle mass and preventing unintentional weight loss often become higher priorities than prolonged fasting. When it comes to young adults, ensuring adequate nutrition for growth, athletic performance & mental health may be more important than restricting eating windows. When it comes to working professionals in IT and other desk-based careers, I often observe that intermittent fasting can reduce unnecessary snacking and improve meal planning but only when balanced with regular movement, good sleep & nutritious meals.
How to do intermittent fasting
Patients frequently ask, "How to do intermittent fasting?" If appropriate, consider these general principles:
- Begin gradually with a 12-hour overnight fast.
- Increase the fasting window slowly if well tolerated.
- Stay well hydrated.
- Focus on nutrient-dense whole foods during eating periods.
- Consume adequate protein.
- Include healthy fats and fibre.
- Continue regular physical activity.
- Prioritize adequate sleep.
- Stop fasting and seek medical advice if significant dizziness, weakness, or other concerning symptoms develop.
Sometimes as a doctor we need to put ourselves in the patient's shoes to realize that adding another rigid rule to an already stressful life may not improve health. For some people, reducing stress, improving sleep & eating balanced meals consistently will provide greater benefits than fasting.
Different levels of fasting
People sometimes refer to different levels of fasting based on duration.
These include:
- Overnight fasting (10–12 hours)
- Time-restricted eating (12–18 hours)
- Extended fasting (24 hours or longer)
- Therapeutic fasting under medical supervision
Longer fasts are not necessarily better & more is not always healthier.
Intermittent fasting is not suitable for everyone. An individualized assessment is important, particularly for people who are pregnant, breastfeeding, have diabetes, a history of eating disorders, or other significant medical conditions.
Final thoughts
Intermittent fasting is a flexible eating strategy that may offer meaningful health benefits for many individuals, including improved metabolic health, weight management & better eating habits. However, it is not a magic solution, nor is it appropriate for everyone. The greatest fasting benefits occur when intermittent fasting is combined with a nutritious diet, regular physical activity, restorative sleep & healthy lifestyle habits.
If you are considering starting an intermittent fasting diet, speak with a qualified healthcare professional to determine whether it is appropriate for your individual health needs. As a primary care Naturopathic Doctor, I help patients develop personalized nutrition strategies that support long-term health while ensuring they are both safe and sustainable.
The naturopathic approach to intermittent fasting
As a wellness specialist, I view intermittent fasting as one of many nutritional tools not a universal prescription. After treating many patients, a Naturopathic Doctor defines success not simply by the number on the scale but by improvements in energy, metabolic health, digestion, sleep, laboratory markers, body composition & long-term sustainability.
Before recommending intermittent fasting, I assess medical history, medications, blood sugar regulation, digestive health, hormone balance, nutritional status, activity level, stress and personal goals. Nutrition Counselling Services can help patients explore safe, realistic, and personalized eating strategies based on their health needs and lifestyle.
If you are considering intermittent fasting for weight, energy, digestion, or metabolic health, Aspire Natural Health may help you approach it safely and realistically. Our naturopathic team can review your health history, eating patterns, lifestyle & wellness goals to explore whether fasting is suitable for you. Book a personalized nutrition consultation before making major changes to your routine.
FAQ’s
What are the 5 benefits of intermittent fasting?
Five possible benefits of intermittent fasting include modest weight loss, improved calorie control, better blood sugar regulation, improved insulin sensitivity & support for some heart-health markers such as blood pressure, cholesterol & inflammation. These benefits depend on food quality, total calorie intake, sleep, activity level & individual health conditions. Intermittent fasting is not a guaranteed weight-loss method for everyone.
What happens after 7 days of intermittent fasting?
After 7 days, some people may notice less late-night snacking, reduced bloating, small water-weight changes, more awareness of hunger patterns, or a more structured eating routine. Others may feel headaches, irritability, fatigue, or strong hunger while adjusting. Major fat loss in one week is usually limited; Harvard notes that daily 16-hour fasting may average about half a pound of weight loss per week for some people.
Is daily 16-hour fasting healthy?
Daily 16-hour fasting, often called the 16:8 method, may be reasonable for some healthy adults when meals are balanced and enough nutrients are consumed. However, it may not be suitable for people who are pregnant or breastfeeding, under 18, underweight, have a history of eating disorders, have diabetes, take blood-sugar-lowering medication, or have certain medical conditions. Medical guidance is important before starting.
How many hours a day is intermittent fasting?
Intermittent fasting can vary. A common method is 16:8, where you fast for 16 hours and eat within an 8-hour window. Some people use 12:12, 14:10, 18:6, alternate-day fasting, or 5:2 fasting. The best fasting window is the one that is safe, sustainable & still allows enough protein, fibre, fluids & nutrients.
Can I lose 10 kg in 2 months with intermittent fasting?
Losing 10 kg in 2 months may happen for some people, especially with a higher starting weight, but it is not guaranteed and may be too aggressive for many. Ten kilograms is about 22 pounds in around 8 weeks, which is faster than the commonly recommended gradual pace of about 1 to 2 pounds per week. A safer plan should focus on sustainable fat loss, muscle preservation & metabolic health.
What is the golden rule of intermittent fasting?
The golden rule of intermittent fasting is: do not use fasting as an excuse to overeat or ignore nutrition quality during your eating window. Your meals still matter. Focus on whole foods, protein, vegetables, fibre, healthy fats, hydration & consistent timing. Intermittent fasting works best when it supports a balanced lifestyle, not when it becomes extreme or restrictive.
