Fasting: Tool or Lifestyle?

“To lengthen thy life, lessen thy meals.”

— Benjamin Franklin

Fasting has become one of the most talked about and most misunderstood health practices of the last decade. For some it is a daily lifestyle that has transformed their metabolic health, energy and body composition. For others it is an occasional tool deployed at specific moments for specific purposes. And for a meaningful subset of people, particularly women navigating hormonal transition, certain approaches can do more harm than good.

The truth is that fasting is not one thing. It is a spectrum of practices, each with a distinct physiological purpose and a different degree of appropriateness depending on who you are, where you are in life and what you are trying to achieve.

Which approach applies to you?

• Looking to improve metabolic health and body composition? Intermittent fasting is your starting point

• Want a periodic reset for your gut and cellular health? The 24 hour fast is the tool

• Interested in a more significant biological intervention? The 72 hour fast is in a category of its own

Read the section most relevant to you, or read all three and build your own fasting strategy from the ground up.

Intermittent Fasting Cheat Sheet

What it is

A daily eating pattern that restricts food intake to a set window, typically eight hours, with the remaining sixteen hours fasted. The 16:8 model is the most well researched and widely used, but the window is customisable. Some prefer to skip breakfast and eat between noon and eight in the evening. Others eat earlier and skip dinner. Neither is superior. The best window is the one you can sustain consistently.

What to consume during the fasting window

Water: essential and unlimited

Black coffee: acceptable, no milk or sweetener

Plain herbal teas: chamomile, peppermint and green tea are all good options

Electrolytes: a small pinch of sea salt or a calorie-free electrolyte supplement helps maintain mineral balance during longer windows, particularly if you train in the morning

Anything containing calories breaks the fast and should be avoided until your eating window opens.

How to break it

Break your fast with a protein-led meal rather than a high carbohydrate one. This blunts the post-fast insulin spike, supports muscle protein synthesis and extends satiety. Good options include:

• Two to three eggs with avocado and smoked salmon

• A portion of grilled fish with leafy greens and olive oil

• Full fat Greek yoghurt with a handful of mixed nuts and berries

• A protein shake blended with almond butter and a banana

Avoid breaking your fast with refined carbohydrates or sugary foods, which will spike blood sugar rapidly after a period of depletion.

Age and gender considerations

Men in midlife: 16:8 is generally well tolerated. Can extend toward 18:6 as they adapt

Perimenopausal women: Start with twelve to fourteen hours and extend gradually, monitoring for disrupted sleep, increased irritability or worsening hormonal symptoms

Post-menopausal women: Typically tolerate longer windows well and can approach intermittent fasting with similar flexibility to men

Anyone with a history of disordered eating: Approach any structured fasting practice with caution and ideally with professional support.

24 Hour Fast Cheat Sheet

What it is

A periodic extended fast lasting a full twenty-four hours, typically structured as dinner to dinner.

Used a few times per year rather than as a daily habit, it deepens the autophagy response

beyond what daily intermittent fasting can achieve and gives the gut a meaningful period of

complete digestive rest. Emerging research links periodic extended fasting to improved

microbiome diversity and reduced intestinal inflammation.

What to consume during the fast

Water: consistently throughout, essential

Electrolytes: sea salt, a magnesium supplement or a quality calorie-free electrolyte drink such as LMNT or Ultima Replenisher

Black coffee and plain herbal teas: chamomile and peppermint are particularly good for digestive calm during a gut rest day

Avoid anything containing calories

How to break it

The meal that breaks a 24 hour fast deserves as much thought as the fast itself:

Start small: 

• bone broth, a small portion of steamed fish or eggs, or a warm bowl of miso soup

• Two to three spoonfuls of kefir or sauerkraut helps reintroduce beneficial bacteria gently

• Wait at least one hour before eating more substantially• Return to normal meal volumes gradually, not immediately

• Avoid large, heavy meals straight after breaking the fast. The digestive system has been at rest and needs a gentle reintroduction

Age and gender considerations

Men in midlife: A quarterly 24 hour fast is well tolerated as a metabolic and gut reset

Menstruating women: The follicular phase (two weeks following menstruation) is the most

appropriate timing. Avoid the luteal phase (two weeks before menstruation) as hormonal

sensitivity is higher

Post-menopausal women: The cyclical consideration no longer applies. Timing can be

chosen freely

72 Hour Fast Cheat Sheet

What it is

A significant physiological intervention lasting three full days without food. This is not a regular

practice. It is a periodic deep cleanse for the gut, immune system and the body's cellular repair

mechanisms. Research from Professor Valter Longo at the University of Southern California

has shown that fasting of this duration triggers immune cell regeneration, accelerates the

clearing of senescent cells and produces a meaningful reset of the gut microbiome. In short, its one of the

most profound biological interventions available outside of a clinical setting.

What to consume during the fast

Electrolytes are non-negotiable: use LMNT, Ultima Replenisher or a homemade mix of sea salt, cream of tartar and magnesium citrate dissolved in water. Their absence produces the headaches, fatigue and cramps most people mistakenly attribute to the fast itself

Water: consistently and generously, aim for three litres per day minimum

Black coffee: acceptable in the first day or two, though some find it amplifies hunger later in the fast

Herbal teas: ginger tea is useful for managing hunger and nausea. Peppermint supports digestive calm

Bone broth: opt for a quality grass-fed version such as Kettle and Fire or homemade. While technically containing calories, its mineral content and gut-supportive properties make it a useful option.

How to enter and exit the fast

The day before:

• Eat simply and lightly

• Reduce carbohydrate intake and avoid processed foods

• Eat your last meal early in the evening to ease the transition into ketosis

Breaking the fast:

• Start with four to six ounces of bone broth or a small portion of kefir or sauerkraut to reintroduce beneficial bacteria

• Follow with a small amount of easily digestible fruit such as watermelon, papaya or berries after thirty minutes

• After one hour, a small portion of steamed white fish, scrambled eggs or cooked courgette and carrot

• Avoid red meat, raw vegetables, legumes and heavy fats for the first twenty-four hours after breaking the fast

Exercise during the fast

Keep movement light: 

• walking, gentle mobility work and stretching are appropriate

• Avoid high intensity training, heavy resistance work or anything that significantly elevates heart rate

• This is a time for rest and restoration, not performance

Age and gender considerations

Men in midlife in good health: Can be approached one to four times per year depending on goals and response

Menstruating women: The follicular phase is the most appropriate timing

Post-menopausal women: Can be timed freely, one to four times per year

Not appropriate for: Those with a history of disordered eating, significant metabolic conditions, cardiovascular disease, or those who are pregnant or breastfeeding

Important: This is not a starting point. Prior experience with shorter fasting protocols is recommended before attempting a 72 hour fast