A nutritionist has explained the health benefits of fasting, saying the diet trick 'flips a switch' in your body that is good for brain health gut health, inflammation and weight loss. Sandra Cohen, a Doctify rated functional nutritionist, has explained the benefits, risks, and what to keep in mind if you are considering fasting.

Sandra said: “Fasting triggers a metabolic switch, shifting the body’s fuel source from stored glycogen to fatty acids, leading to ketosis. This metabolic shift enhances mitochondrial efficiency, supports cellular repair, and can improve cognitive function and mental well-being. These mitochondrial benefits, combined with fasting’s ability to reduce inflammation, regulate insulin sensitivity, support gut health, and promote autophagy, make it a powerful tool in personalized health strategies for metabolic, neurological, and inflammatory conditions."

She added: “Staying hydrated is crucial. Water supports metabolism, detoxification, and electrolyte balance. Many fasting regimens allow herbal teas, black coffee, or bone broth to support hydration and electrolyte levels."

Sandra said:“ Medical supervision is recommended for prolonged fasts to ensure nutritional adequacy and to prevent excessive metabolic stress. Ultimately, fasting should be a supportive tool, not a stressor. Listening to your body and adjusting fasting frequency, duration, and dietary intake accordingly will ensure that it enhances health rather than disrupting it”.

Benefits of fasting include:

  • Metabolic health - Enhances insulin sensitivity, lowers blood sugar, and reduces the risk of type 2 diabetes
  • Cognitive benefits - Supports brain health by increasing BDNF (brain-derived neurotrophic factor), which may reduce the risk of neurodegenerative diseases
  • Weight loss and fat burning - Promotes fat oxidation and reduces inflammation
  • Longevity and cellular repair - Induces autophagy, which removes damaged cells and may slow ageing
  • Gut health - Allows the digestive system to rest, reducing bloating and improving gut microbiome diversity

However, while fasting offers numerous benefits, it may also pose certain risks.

Risks of fasting include:

  • Blood sugar imbalances - Can lead to hypoglycemia, especially in diabetics
  • Hormonal disruptions - May negatively impact menstrual cycles or thyroid function in some individuals
  • Muscle loss - Extended fasting without adequate protein intake can lead to muscle breakdown
  • Electrolyte imbalances - Prolonged fasting without replenishing sodium, potassium, and magnesium can cause dizziness, fatigue, or heart palpitations

Sandra said fasting may not be suitable for some people, including :

  • Diabetics on medication (risk of hypoglycaemia)
  • Those with adrenals or/and thyroid dysfunction
  • Those under chronic stress or sleep disturbances (as it may elevate cortisol)
  • Pregnant/breastfeeding women (increased caloric needs)
  • Those with a history of eating disorders
  • Elderly individuals (risk of muscle loss or frailty)
  • Children/adolescents (as they require continuous nutrients for growth)
  • People with chronic illnesses or recovering from surgery

Breaking a fast with easily digestible, nutrient-dense foods prevents digestive distress. Avoid processed sugars, excessive carbs, or large portions, which may spike blood sugar levels and cause digestive discomfort. Ideal choices might include:

  • Healthy fats (avocado, bone broth, olive oil) – ½ avocado, 1 tbsp olive oil
  • Lean proteins (eggs, fish, chicken) – ¼ of the plate
  • Non-starchy vegetables (steamed spinach, zucchini, cucumbers) -½ of the plate
  • Fermented foods (sauerkraut, kimchi) to support gut health - 2 tbsp