28th May 2024

Understanding the long-term side effects of intermittent fasting

Looking for an effective weight loss programme that also holds a number of long-term mental and physical benefits? Good news – intermittent fasting definitely fits that bill! However, it’s just as crucial to understand the long-term side effects of intermittent fasting to ensure you’re staying safe throughout the process. Here, we’re going to explore the broader perspective of intermittent fasting, examining if there is a sustained impact on your metabolism, longevity, or overall health.

Amidst the noise of fad diets and fleeting health trends, The Fast 800 stands as an evidence-based programme backed by scientific research and the expertise of Dr Michael Mosley. Through this knowledge and expertise, we’re able to give guidance that promises to support long-term health success through our 5:2 diet. Let’s begin by looking at the benefits of long-term intermittent fasting:

What are the benefits of long-term intermittent fasting

Lower risk of type 2 diabetes

Long-term intermittent fasting has been associated with a reduced risk of type 2 diabetes by improving insulin sensitivity and blood sugar control over time. By promoting metabolic health and reducing insulin resistance, intermittent fasting may help prevent the onset of type 2 diabetes and its associated complications.1

Improved heart health

Research suggests long-term intermittent fasting may improve heart health by reducing risk factors such as high blood pressure, cholesterol levels, and inflammation. By promoting weight loss, enhancing metabolic function, and reducing oxidative stress, intermittent fasting may support cardiovascular health and reduce the risk of heart disease.2

Preserved cognitive function and brain health

Long-term intermittent fasting may help preserve cognitive function and promote brain health by supporting the production of brain-derived neurotrophic factor (BDNF) and ketone bodies. These neuroprotective effects may reduce the risk of neurodegenerative diseases such as Alzheimer’s and support overall cognitive function and brain health as individuals age.3

Reduced risk of cancer

Emerging research suggests that long-term intermittent fasting may help reduce the risk of cancer by inhibiting tumour growth, promoting cellular repair mechanisms, and reducing inflammation. By supporting immune function, enhancing cellular health, and reducing oxidative stress, intermittent fasting may contribute to lower cancer risk and improve overall cancer outcomes.4

Enhanced cellular repair

Intermittent fasting promotes cellular repair mechanisms such as autophagy, which helps remove damaged cellular components and support cellular rejuvenation. By reducing oxidative stress and promoting cellular health, intermittent fasting may enhance cellular repair and contribute to overall health and longevity.5

Prevention of Alzheimer’s disease

Studies suggest that long-term intermittent fasting may help prevent Alzheimer’s disease by reducing risk factors such as inflammation, oxidative stress, and insulin resistance. By promoting brain health, supporting cognitive function, and reducing the accumulation of amyloid plaques, intermittent fasting may help prevent the onset of Alzheimer’s disease and preserve brain function as individuals age.6, 7

Long-term side effects of intermittent fasting

While there are numerous benefits, it’s essential to consider the potential long-term side effects of intermittent fasting. This helps to create a balanced argument and enables you to make informed decisions about your health journey. Here are some factors to keep in mind:

  • Disordered eating patterns: For some individuals, intermittent fasting may exacerbate disordered eating behaviours or trigger unhealthy relationships with food. Intermittent fasting is not suitable for those with previous experience of disordered eating.8
  • Hormonal imbalances: In rare cases, intermittent fasting can affect hormone levels, potentially disrupting menstrual cycles for some women or impacting hormone regulation. If you experience hormonal imbalances or menstrual irregularities, consult with a healthcare professional for personalised guidance.8

Embrace professionally guided long-term fasting for weight loss

While there can be long-term side effects of intermittent fasting, the results are positive for most participants. By staying informed about potential side effects and monitoring your body’s response to intermittent fasting, you can optimise your health journey and reap the benefits of this dietary approach while minimising risk.

The Fast 800 solutions are tailored to your goals, and we’ll encourage you to adapt your approach throughout the process to ensure the success of your long-term fasting for weight loss. We adopt the 5:2 diet in our fasting – a flexible diet that aims to work with you in achieving your health goals. However, we also offer approaches like the Way of Life with no fasting days, for those who have reached their weight loss goals and are looking to focus on their metabolic health.

The sustainability of the 5:2 Diet

The sustainability of the 5:2 fasting method is rooted in its adaptability and enduring health advantages. Unlike stringent diets, the 5:2 approach offers a flexible calorie-restriction strategy, making it feasible for extended adherence. By allowing individuals to choose their fasting days and seamlessly integrate fasting into their weekly schedules, the 5:2 offers incredible long-term sustainability. As well as this, the emphasis on consuming Mediterranean-style whole foods fosters metabolic health and satiety.

With its proven efficacy in targeting visceral fat, enhancing insulin sensitivity, and facilitating cellular repair, the 5:2 diet delivers comprehensive health benefits beyond weight management. Choose a more sustainable approach to long-term health; choose the 5:2 method.

Discover The Fast 800 weight loss programme

For those seeking a comprehensive approach to weight loss and better health, The Fast 800 offers various services designed to support your journey. Our 5:2 weight loss programme, products, and resources are rooted in the latest scientific research, ensuring a game-changing approach to healthy living.

Whether you’re embarking on a 12-week supported programme, maintaining progress with an ongoing monthly subscription, engaging with our vibrant community, or exploring our range of supportive products, The Fast 800 is committed to empowering you with the tools and knowledge to achieve long-term success. Join us on the journey to a healthier, happier you.

Long-term side effects of intermittent fasting – Frequently Asked Questions

How can I maintain a balanced approach to intermittent fasting for sustained health benefits?

Here are our top tips for a sustainable approach to intermittent fasting:

  • Choose nutrient-dense foods: Focus on whole, unprocessed foods during eating windows to ensure you meet your nutritional needs. Add plenty of fruits, vegetables, lean proteins, and healthy fats to your meals.
  • Stay hydrated: Drink plenty of water throughout the day, especially during fasting periods, to support hydration and overall wellbeing.
  • Listen to your body: Pay attention to hunger cues, energy levels, and overall wellness. If you feel fatigued or unwell, consider adjusting your fasting schedule or meal timing to suit your needs better.
  • Include physical activity: Incorporate regular exercise into your routine to support muscle health, metabolism, and overall fitness. Strength training can help preserve muscle mass during intermittent fasting.
  • Practice mindful eating: Be present and attentive during meals, savour each bite, and pay attention to hunger and fullness cues. Avoid overeating during eating windows to maintain a balanced intake of calories.

Can intermittent fasting cause muscle loss over time?

No, intermittent fasting does not inherently cause muscle loss over time. In fact, when done correctly, intermittent fasting can help preserve muscle mass while promoting fat loss. Research suggests that intermittent fasting may stimulate the production of human growth hormone (HGH), which plays a role in muscle preservation and metabolic health.

Additionally, intermittent fasting is often combined with resistance training, supporting muscle maintenance and growth. However, it’s essential to ensure an adequate protein intake and overall calories during eating windows to support muscle health and prevent potential muscle loss.


Ju Young Kim. Optimal Diet Strategies for Weight Loss and Weight Loss Maintenance. J Obes Metab Syndr. 2021 Mar 30; 30(1): 20–31. doi: 10.7570/jomes20065. PMID: 33107442.

Ju Young Kim. Optimal Diet Strategies for Weight Loss and Weight Loss Maintenance. J Obes Metab Syndr. 2021 Mar 30; 30(1): 20–31. doi: 10.7570/jomes20065. PMID: 33107442.

Teresa Vanessa Fiorentino. Effects of Intermittent Fasting on Brain Metabolism. Nutrients. 2022 Mar; 14(6): 1275. doi: 10.3390/nu14061275. PMID: 35334932.

Valter D. Longo, Maira Di Tano, Mark P. Mattson and Novella Guidi. Intermittent and periodic fasting, longevity and disease. Nat Aging. 2021 Jan; 1(1): 47–59. doi: 10.1038/s43587-020-00013-3. PMID: 35310455.

Andrea Mulas, Sofia Cienfuegos, Mark Ezpeleta, Shuhao Lin, Vasiliki Pavlou, and Krista A. Varady. Effect of intermittent fasting on circulating inflammatory markers in obesity: A review of human trials. Front Nutr. 2023; 10: 1146924. doi: 10.3389/fnut.2023.1146924. PMID: 37139450.

Anna Obermayer, Norbert J. Tripolt, Peter N. Pferschy, Harald Kojzar, Angela Jacan, Markus Schauer, Faisal Aziz, Abderrahim Oulhaj, Felix Aberer, Caren Sourij, Barbara Obermayer‐Pietsch, Vanessa Stadlbauer, and Harald Sourij. INTERmittent FASTing in people with insulin‐treated type 2 diabetes mellitus – the INTERFAST‐2 study protocol. Diabet Med. 2022 Jun; 39(6): e14813. doi: 10.1111/dme.14813. PMID: 35179802.

Alby Elias, Noushad Padinjakara and Nicola T Lautenschlager. Effects of intermittent fasting on cognitive health and Alzheimer’s disease. Nutr Rev. 2023 Sep; 81(9): 1225–1233. doi: 10.1093/nutrit/nuad021. PMID: 37043764.


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