What is Intermittent Fasting?

Intermittent fasting involves cycling between periods of eating and fasting. It doesn’t prescribe what you eat but rather when you eat. Popular methods include the 16/8 method (fasting for 16 hours, eating within an 8-hour window), the 5:2 approach (eating normally five days a week, then consuming only 500-600 calories on two non-consecutive days), and the Eat-Stop-Eat method (involving 24-hour fasts once or twice a week).

Why Does This Work and How Do I Do This? 

Basically – with fewer hours to consume calories, you tend to eat fewer calories. There are also several metabolic benefits described later in the article.  It’s best to start gradually.  Try delaying breakfast for an hour after you wake up. Start your morning with a full glass of water.  Coffee and tea is fine as well but ideally avoid sugar and milk.  Try to not eat after dinner.  Have a good protein meal with dinner to help with satiety.  See how that feels. In a few days, see if you can fast longer – basically waiting longer for breakfast and making sure you don’t eat anything after dinner.  For the most commonly used 16/8 method, if you typically eat dinner at 6pm, don’t eat breakfast until 10am. The premium version of MyFitnessPal has a time tracker if your eating times are variable.  Make sure to drink plenty of water while fasting.  Protein with every meal will help you fill up during your eating window.  It’s ok to fall off the wagon if you have a busy day or if your work schedule doesn’t allow eating breakfast that late!  Intermittent fasting just a few days a week can still help.

Weight Loss Medication and Intermittent Fasting:

Medical weight medications like Semaglutide and Tirzepatide, can be significantly beneficial when combined with intermittent fasting. These medications work by mimicking hormones that regulate appetite and insulin secretion, thereby reducing hunger and improving insulin sensitivity. This mechanism complements intermittent fasting, which also aims to improve metabolic flexibility and insulin sensitivity. When fasting, the body shifts from using glucose as its primary energy source to using stored fat, leading to weight loss. The appetite-suppressing effects of these medications can make fasting periods more manageable, reducing the likelihood of overeating during eating windows.

The Science Behind Intermittent Fasting (IF) and Weight Loss:

The principle behind intermittent fasting is that it helps the body to utilize fat stores as fuel. Intermittent fasting helps induce ketosis and autophagy, processes that play crucial roles in maintaining cellular health and metabolism.

Ketosis occurs when the body starts to burn fat for energy instead of carbohydrates, which typically happens during periods of reduced food intake. When the body’s glucose stores are depleted, it turns to stored fats, breaking them down into ketones, which then serve as an alternative energy source. The transition to ketosis during IF is facilitated by the extended periods without food intake, allowing insulin levels to decrease and fat cells to release stored fatty acids. These fatty acids are transported to the liver, where they are converted into ketones. This process not only aids in weight loss by burning stored fat but also can result in increased energy levels, improved mental clarity, and a reduction in inflammation.The ideal duration of fasting to enter ketosis varies among individuals, influenced by factors like metabolism, diet, and physical activity levels. Generally, it can take anywhere from 12 to 36 hours of fasting for the body to enter ketosis. For many, a fasting window of around 16-24 hours is effective for inducing ketosis. This can be achieved through various IF methods, such as the 16/8 method (fasting for 16 hours and eating within an 8-hour window) or the OMAD (One Meal A Day) approach.

Autophagy, derived from the Greek words for “self” (auto) and “eating” (phagy), is the body’s way of cleaning out damaged cells and regenerating newer, healthier cells. It involves the degradation and recycling of cellular components, playing a vital role in cellular maintenance and repair. During fasting periods, the reduced intake of nutrients triggers autophagy. This is because, in the absence of external sources of energy (such as food), the body seeks alternative internal sources. It starts breaking down and recycling dysfunctional proteins and organelles within cells. This process is not only essential for cellular health and function but also has implications for weight loss and overall wellness. Autophagy aids in weight loss by improving metabolic efficiency and reducing inflammation. It helps in the breakdown of fat cells and the efficient use of energy, contributing to a reduction in body weight. Moreover, autophagy is linked to improved insulin sensitivity, which can further aid in the management of body weight and reduce the risk of metabolic diseases.

The concept of IF closely aligns with how our ancestors used to eat. Historically, humans did not have constant access to food and often went through periods of fasting due to food scarcity. This natural cycle of eating and fasting suggests that our bodies may be adapted to this pattern, which can explain the health benefits associated with IF. By mimicking this ancestral eating pattern, IF supports our natural metabolic processes, encouraging the body to function more efficiently.

Evidence Supporting Intermittent Fasting for Weight Loss:

1. Improvements in Hunger, Mood, and Sleep: A study by researchers from King’s College London, presented at the European Nutrition Conference in 2023, investigated the effects of a 10-hour eating window followed by a 14-hour fasting period. This study, involving 37,545 participants using the ZOE Health app, demonstrated that such an eating pattern led to higher energy levels, improved mood, and lower hunger levels. Participants who consistently followed this eating schedule experienced greater benefits than those who varied their eating window daily. The study highlighted that even a less restrictive fasting window of 10 hours could yield significant health benefits​​.
2. Impact on Alzheimer’s Disease: Research from the University of California San Diego School of Medicine has shown potential benefits of IF in the context of Alzheimer’s disease. In a study published in Cell Metabolism, mice that were fed on a time-restricted schedule showed improvements in memory and reduced accumulation of amyloid proteins in the brain. This research points towards the potential of IF as a treatment approach for Alzheimer’s disease, particularly through the correction of circadian disruptions. The feeding schedule in this study was equivalent to about 14 hours of fasting each day for humans​​​​.
3. Comparison with Calorie Restriction in Diabetes Risk: A significant study published in Nature Medicine in 2023 compared intermittent fasting plus early time-restricted eating (iTRE) with calorie restriction (CR) and standard care in adults at risk of type 2 diabetes. This randomized controlled trial involved 209 participants and found that iTRE led to a greater improvement in postprandial glucose metabolism than CR. The iTRE group consumed 30% of their energy requirements between 0800 and 1200 hours, followed by a 20-hour fasting period on three nonconsecutive days per week. The study observed not only improvements in glycemic control but also reductions in systolic and diastolic blood pressure, fasting triglycerides, total cholesterol, and low-density lipoprotein (LDL) levels. Additionally, iTRE was more effective in reducing β-hexosaminidase activity, a marker associated with liver health and diabetes​​​​​​​​​​.

These studies collectively demonstrate the diverse health benefits of intermittent fasting, ranging from improved mood and energy levels to potential therapeutic effects in Alzheimer’s pathology and enhanced metabolic outcomes in individuals at risk of type 2 diabetes. It’s important to note that while these results are promising, further research, especially in human trials, is necessary to fully understand the long-term impacts and optimal protocols of intermittent fasting.

Remember, the journey to a healthier weight is a marathon, not a sprint. Incorporating intermittent fasting into a balanced lifestyle that includes a nutritious diet and regular physical activity can be the key to unlocking your weight management potential.

This post is designed to educate and should not replace professional medical advice. Readers are encouraged to consult a healthcare provider before starting any new weight loss strategy, including intermittent fasting.

Learn more:

Steering Clear of Sugary Snacks

Eat More Protein!

Counting Calories