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Intermittent fasting, or ketogenic diet, is a way to maintain or lose weight, improve health, prevent disease, and more. On the contrary, you should also know that it’s not the perfect way to lose weight for everyone. There are several factors to consider.
In this blog, we want to highlight what’s happening in your body while you’re depriving it of calories.
Intermittent fasting for weight loss
The basic biology behind intermittent fasting is the switch of energy sources from glucose to triglycerides during interventions in calorie intake for the body. The metabolic switch often leads to metabolic stress and thereby makes the body work a bit extra to run its basic functions.
Rafael de Cabo, PhD, submitted his research on the effects of intermittent fasting on health, ageing, and disease to the New England Journal of Medicine back in December 2019. He suggested that not eating for 6 hours and fasting for 18 hours can trigger a major metabolic switch from glucose to ketone-based energy and decrease incidents of obesity and cancer.
The most common methods are fasting on alternate days, for whole days with a specific frequency per week, or during a set time frame. [3]
- Alternate-day fasting—Alternating intermittent fasting for weight loss between days of no food restriction with days that consist of one meal that provides about 25% of daily calorie needs.
- Whole-day fasting—1-2 days per week of complete fasting or up to 25% of daily calorie needs, with no food restriction on the other days. Example: The 5:2 diet approach advocates no food restriction five days of the week, cycled with a 400-500 calorie diet the other two days of the week.
- Time-restricted feeding—Following a meal plan each day with a designated time frame for fasting. Example: Meals are eaten from 8 a.m. to 3 p.m., with fasting during the remaining hours of the day.
A representation of what happens during intermittent fasting for weight loss.
Insulin Sensitivity and Fat Storage
Intermittent fasting impacts insulin sensitivity, a crucial factor in weight management. When we eat, especially foods high in carbohydrates, our blood sugar levels rise, prompting the pancreas to release insulin. Insulin facilitates the uptake of glucose into cells for energy, but it also signals the body to store excess glucose as fat.
Over time, repeated insulin spikes can lead to insulin resistance, making it harder for the body to respond to the hormone efficiently.
Intermittent fasting for weight loss helps regulate insulin levels by promoting periods of low insulin activity during fasting. This, in turn, enhances insulin sensitivity, making it easier for the body to manage blood sugar and reducing the likelihood of excess glucose being stored as fat.
Hormonal Changes and Fat Burning
Fasting triggers a cascade of hormonal changes that play a pivotal role in weight loss. One key hormone affected is norepinephrine, which increases during fasting. Elevated norepinephrine levels stimulate the breakdown of stored fat into free fatty acids, promoting fat burning for energy.
Additionally, fasting leads to an increase in human growth hormone (HGH). HGH is crucial for maintaining lean muscle mass and promoting fat utilization. As muscle is preserved and fat becomes a primary energy source, intermittent fasting can contribute to a more favourable body composition during weight loss.
Cellular Repair and Autophagy
Beyond weight loss, intermittent fasting supports cellular repair processes through a phenomenon called autophagy. During fasting, cells undergo a self-cleaning process where they remove damaged components and recycle them for energy. This process helps optimize cellular function and may have anti-aging effects.
Furthermore, autophagy extends to the removal of dysfunctional mitochondria, the energy-producing organelles within cells. This mitochondrial turnover enhances cellular efficiency, potentially improving overall metabolic health and contributing to weight loss.
Caloric Restriction and Metabolic Rate
Intermittent fasting for weight loss often leads to a natural reduction in caloric intake, a fundamental factor in weight loss. By limiting the eating window, individuals may find it challenging to consume as many calories as they would with a traditional eating pattern. This caloric restriction creates an energy deficit, prompting the body to utilize stored fat for fuel.
Contrary to common misconceptions, intermittent fasting does not necessarily slow down the metabolism. Some studies suggest that short-term fasting may slightly increase metabolic rate, enhancing the body’s ability to burn calories. However, it’s crucial to strike a balance and avoid prolonged fasting, which could have adverse effects on metabolism.
Inflammation and Oxidative Stress
Chronic inflammation and oxidative stress are associated with various health issues, including obesity. Intermittent fasting for weight loss exhibits anti-inflammatory and antioxidant effects, helping to mitigate these risk factors.
Fasting periods reduce the production of inflammatory markers and promote the activation of pathways that combat oxidative stress. By addressing these underlying factors, intermittent fasting contributes not only to weight loss but also to overall health and disease prevention.
Intermittent fasting offers a compelling biological framework for weight loss. By influencing insulin sensitivity, hormonal balance, cellular repair, caloric intake, and inflammatory processes, this dietary pattern addresses multiple facets of the complex interplay between biology and weight management.
Increased Cognitive Function
We know the importance of diet and the gut-brain axis for brain health, but little do we know, that dietary interventions like intermittent fasting also help improve memory and cognitive function.
As suggested by Mònica Bulló, Department of Psychiatry, Donders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands, there are long term effects of IF on the development and progress of brain disorders as well.
As with any lifestyle change, it’s essential to consult with healthcare professionals before embarking on an intermittent fasting journey, ensuring that individual health needs and goals are considered. Embracing intermittent fasting as part of a holistic approach to health may unlock not only the door to weight loss but also to a healthier and more resilient body.
