Eating less often to improve health? That’s the idea behind intermittent fasting (IF), a dietary approach that sparks both curiosity and debate. Some adopt it for weight loss, while others believe in its potential benefits for energy, digestion, or even longevity.
But is it really effective? What are the benefits and limitations? How can you try it safely? Before getting started, let’s explore what the registered dietitians and nutritionists from our partner ÉquipeNutrition have to say.
What is intermittent fasting?
Intermittent fasting is an eating pattern that alternates between periods of fasting and eating. Unlike traditional calorie restriction, IF focuses more on when you eat rather than what you eat.
The main types of intermittent fasting
There are several ways to practice intermittent fasting, depending on the length of fasting and eating periods (1):
- Time-restricted eating: Eating is limited to a set time frame each day, such as 16 hours of fasting and an 8-hour eating window (16/8), or variations like 14/10 or 20/4, based on individual tolerance. For example, with the 16/8 cycle, you could eat your meals between 10 a.m. and 6 p.m. and then fast until 10 a.m. the following morning.
- Alternate-day fasting: Alternating between regular eating days and days of partial fasting (500-600 kcal) or complete fasting. Examples include every-other-day fasting or the 36/12 method (36 hours of fasting, 12 hours of eating).
- Extended fasting: Fasting for 24 hours or more, such as the Eat-Stop-Eat method (one or two full fasting days per week) or the 5:2 approach (reduced calorie intake on two days per week).
- Spontaneous fasting: Skipping meals occasionally, based on hunger and daily schedule, without a fixed plan.
Potential benefits of intermittent fasting
1. Weight management
Intermittent fasting may promote weight loss by reducing overall calorie intake and improving insulin sensitivity, particularly in overweight individuals or those with metabolic conditions (2). However, its effectiveness varies—some studies find no significant impact in individuals without metabolic issues. It’s not a miracle solution, but rather a tool that should be combined with a balanced diet and healthy lifestyle.
2. Possible health benefits
Intermittent fasting may help stabilise blood sugar levels and optimise energy utilisation in the body. This could be beneficial for people at risk of diabetes, as it may enhance insulin regulation (2). Some studies suggest anti-inflammatory effects that could support heart health, but evidence remains limited (3).
⚠️ Important: If you take medication—especially for diabetes—consult a healthcare professional before trying intermittent fasting.
3. Potential impact on aging
Intermittent fasting may activate a cellular regeneration process called autophagy, which helps eliminate damaged cells and maintain overall health. However, these effects have been observed mainly in animal studies, and human research is still limited (1).
4. Other motivations
Intermittent fasting isn’t just about weight loss. Some use it to simplify their eating routine, improve digestion, or boost concentration (4). There’s also potential for cognitive and memory benefits, though more research is needed.
Possible side effects of intermittent fasting
While Intermittent fasting can offer benefits, its effects vary from person to person. Some studies highlight positive outcomes, while others report side effects. Here are some common challenges (4-6):
1. Adjustment period (5)
- Fatigue and irritability
- Dizziness
- Fluctuating energy levels
2. Hydration and electrolyte imbalance (6)
3. Digestive and metabolic effects
- Digestive discomfort: Constipation, bloating, or stomach discomfort (5)
- Low blood sugar: Especially in those sensitive to fasting, including people on diabetes medication (7)
4. Hormonal and metabolic impact
- Hormonal imbalances: Poorly managed fasting can disrupt hormone balance and lead to nutrient deficiencies (5).
- Oxidative stress and fasting glucose levels: Strict fasting protocols could increase oxidative stress and elevate fasting blood sugar levels (7).
5. Psychological and behavioural consequences
- Risk of disordered eating: IF may trigger or worsen eating disorder symptoms in some individuals (5).
If these symptoms persist, adjust your approach or consult a healthcare professional.
How to start intermittent fasting
1. Choose the right approach
- Start with a shorter fasting window (e.g., 12 hours) before gradually increasing it.
- Experiment with different methods to find what suits your lifestyle and energy levels.
2. Focus on balanced nutrition
- Prioritize protein, healthy fats, and fibre for sustained fullness and energy.
- Limit ultra-processed foods and refined sugars.
- Avoid overeating during your eating window.
3. Stay hydrated
- Drink water throughout the day to prevent dehydration.
- Unsweetened tea and coffee are generally allowed during fasting.
- If you experience headaches, add a pinch of salt to your water to maintain electrolyte balance.
4. Listen to your body
- Watch for signs like excessive fatigue, dizziness, or irritability—these may indicate that intermittent fasting isn’t right for you.
- Adjust your plan if needed.
- Consult a healthcare professional if side effects persist.
Is intermittent fasting right for you?
Intermittent fasting can be beneficial for weight management and overall health, but it’s not suitable for everyone. Success depends on a well-balanced diet and a healthy lifestyle.
Before starting, it’s recommended to consult a registered dietitian to determine if this approach aligns with your individual needs and goals.
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References
- Hull, Michael. (2024, August 26). The lowdown on intermittent fasting. Examine.https://examine.com/articles/the-low-down-on-intermittent-fasting/
- Yuan, X., Wang, J., Yang, S., Gao, M., Cao, L., Li, X., Hong, D., Tian, S., & Sun, C. (2022). Effect of Intermittent Fasting Diet on Glucose and Lipid Metabolism and Insulin Resistance in Patients with Impaired Glucose and Lipid Metabolism: A Systematic Review and Meta-Analysis. International journal of endocrinology, 2022, 6999907. https://doi.org/10.1155/2022/6999907
- Mattson, M. P., Longo, V. D., & Harvie, M. (2017). Impact of intermittent fasting on health and disease processes. Ageing research reviews, 39, 46–58. https://doi.org/10.1016/j.arr.2016.10.005
- Boujelbane, M. A., Trabelsi, K., Jahrami, H. A., Masmoudi, L., Ammar, A., Khacharem, A., Boukhris, O., Puce, L., Garbarino, S., Scoditti, E., Khanfir, S., Msaad, A., Msaad, A., Akrout, S., Hakim, A., Bragazzi, N. L., Bryk, K., Glenn, J. M., & Chtourou, H. (2022). Time-restricted feeding and cognitive function in sedentary and physically active elderly individuals: Ramadan diurnal intermittent fasting as a model. Frontiers in nutrition, 9, 1041216. https://doi.org/10.3389/fnut.2022.1041216
- Varady, K. A., Cienfuegos, S., Ezpeleta, M., & Gabel, K. (2021). Cardiometabolic Benefits of Intermittent Fasting. Annual review of nutrition, 41, 333–361. https://doi.org/10.1146/annurev-nutr-052020-041327
- Varady, K. A., Cienfuegos, S., Ezpeleta, M., & Gabel, K. (2022). Clinical application of intermittent fasting for weight loss: progress and future directions. Nature reviews. Endocrinology, 18(5), 309–321. https://doi.org/10.1038/s41574-022-00638-x
- Joaquim, L., Faria, A., Loureiro, H., & Matafome, P. (2022). Benefits, mechanisms, and risks of intermittent fasting in metabolic syndrome and type 2 diabetes. Journal of physiology and biochemistry, 78(2), 295–305. https://doi.org/10.1007/s13105-021-00839-4
