How to Optimise your Diet for Fasting

Written by Liz Withyman
May 23, 2024

This article is about optimising your diet for a fasting lifestyle. If you would like to read more about what you can consume during fasting hours, look out for my upcoming blog: Diet for Fasting: What Can I Consume Without Breaking my Fast?

Medical Disclaimer

I am not a doctor and the information provided in this article is not intended as medical advice. Intermittent fasting may not be suitable for everyone. Please consult your doctor before making any changes to your health regimen, especially if you have any medical conditions or concerns.

How to Optimise Your Diet for Fasting: What to Eat to Support your Fasting Lifestyle

When asked whether when or what you eat is more important for great health, Professor Satchin Panda, Circadian Rhythm and fasting expert answered that this was like asking, Who is your favourite child?!

In other words, you can’t choose between them.

They’re equally important.

Without changing your diet at all, you would improve your health in terms of your gut microbiome, your energy levels and likely your weight purely by fasting for longer and eating all your food within a shortened eating window…

…and conversely you could get a lot of benefit from eating an all real food, wholesome diet without cutting down your eating window.

Either approach is good, but doing both is better.

Better and Easier

Not only is improving your diet as well as your fasting hours better; it’s also easier.

I have found, in my own experience and that of clients, that if you optimise your diet for fasting – by eating a diet that steadies your blood glucose, feeds your gut microbiome and supports your
muscles – you’ll make a fasting practice a whole lot easier to sustain.

You just won’t be as hungry in your fasting windows.

You’ll have more energy.

And conversely, when you have a regular fasting practice, it feels easier and more natural to eat real, whole food, because it’s what your body will crave.

Key Principles of a Diet for Fasting

In this article, we’ll explore some key principles of a diet for fasting and how you can tailor the food you put in your eating window, to maximise the benefits of fasting and make it easy to do.

Understanding the Basics of Fasting

A fasting lifestyle involves cycling between periods of eating and fasting.

If you’re a regular intermittent faster, you might typically follow a 16/8 pattern in which you fast for 16 hours daily, and eat within an 8 hour window (16/8). Or you might have a weekly pattern in which you fast every other day (Alternate Day Fasting).

Or you might sometimes extend your fasts for longer periods.

Fasting / Intermittent Fasting

When I refer to a fasting lifestyle, I include intermittent fasting as well as a regular practice of doing longer fasts such as 24 / 36 / 48 / 72 hours*.

*With longer fasts, it’s important not to jump straight in. You need to train your body to handle longer fasts by establishing an intermittent fasting habit such as 16/8 first, and then extending the fasting window gradually.

The Benefits of a Fasting Lifestyle

  • improved metabolic health
  • fat burning
  • high energy
  • better mood
  • improved skin
  • enhanced cognitive functioning

Longer fasts intensify many of the benefits. The ideal length of fast for you really depends on what outcomes you want. You can read my blog on this topic here.

As well as the incredible health benefits, another wonderful aspect of intermittent fasting reported by many of my clients, is a better relationship with, and more enjoyment of food. For many of them, this new fasting lifestyle gives them a sense of food freedom they’ve not experienced all their adult lives.

So, let’s add:

  • better relationship with food
  • enjoying food more

Optimising Your Diet for Fasting

Regardless of the length of fast you choose, the foundation of a successful fasting lifestyle lies in optimising your diet for fasting. Get this right and you’ll be less hungry, have better mood and sustained energy throughout the fasting period.

Eat Real Food

The #1 rule for optimising your diet for fasting is to eat real food.

And (mostly) avoid ultra-processed food. You can allow yourself a little bit if you really want to, though you’ll find that when you have a fasting practice your body craves mostly real food rather than junk.

What is ultra-processed food?

It’s industrialised rather than natural food, which has had its core ingredients like plant fibre, phytochemicals and microbes stripped out, and artificial chemicals, sugar and processed oils put in. Eating too much of it disrupts metabolic health and promotes inflammation.

You want to minimise this kind of food – you can eat it for taste in small quantities if you want – nothing is ‘off the table’ with intermittent fasting – but don’t eat much, and don’t expect much nutrition from it.

What is Real Food?

Real food is food that hasn’t been industrially processed or its natural properties diminished.

A good rule of thumb is – if Humans made it, it’s processed or ultra-processed, if Nature made it, it’s real food.

Prioritise Protein in your Diet for Fasting

One of the cornerstones of a diet for fasting is adequate protein intake.

Why is this?

Consistent evidence shows that protein is the most effective macronutrient for satiety. In other words, it keeps you feeling full for longer. It’s an extremely important nutrient to get right for other reasons too, but for the purposes of fasting, the satiety factor is crucial. So it’s important to include plenty of protein in an optimal diet for fasting.

Breaking your fast with around 30g protein – whenever you choose to eat your first meal – and then closing your eating window with a further 30g protein, will give the average person (ie not Olympic athletes, who may need more) the right amount of protein to optimise your diet for fasting.

Why is it important to OPEN your eating window with protein?

Why is protein important in the first meal of the day?

There are two important reasons for prioritising protein as part of your diet for fasting, especially when you break your overnight fast.

  1. Firstly, prioritising protein will minimise glucose spikes, and this will reduce your hunger and help you maintain the fasting lifestyle.
  2. Secondly, protein is essential for muscle growth and maintenance, and this supports your health in a number of ways.

1. Minimising Glucose Spikes for Stable Energy

A key aspect of optimising your diet for fasting is minimising glucose spikes and promoting stable energy levels throughout the day. One of the most powerful ways of doing this is to eat a savoury, high protein breakfast.


Because if you start the day with carbohydrate (cereal, toast, fruit, muesli) your blood glucose / sugar levels can spike, prompting a release of insulin to regulate the blood glucose.

What goes up must come down so this spike is typically followed by a crash – a rapid drop in blood sugar that causes feelings of fatigue, hunger and cravings. Aka a glucose rollercoaster.

Consuming savoury foods containing a high level of protein and/or healthy fats will set your day off on the right path, likely keep your energy levels and mood up, and reduce cravings.

(Or if you really want to eat carbohydrates at your first meal, eat them AFTER your protein and healthy fats, as this will slow the absorption of glucose into the bloodstream, and therefore help prevent the glucose rollercoaster effect.)

So a high protein ‘break-the-fast’ meal is an essential part of an optimal diet for fasting.

2. Supporting muscle growth and maintenance

The other good reason to break your fast with sufficient protein in an optimal diet for fasting is to support muscle maintenance. Protein is essential for muscle repair and growth. This is especially true in mid-life.


Starting in our thirties, humans begin to lose muscle mass, a process that accelerates significantly in women during menopause.

Fatal falls account for a shocking number of deaths among over 65’s ranking second only to road traffic accidents! Not to mention the numerous non-fatal injuries that also occur.

So keeping muscles strong is a top health priority. What we do to maximise muscle strength in mid-life is going to massively affect outcomes on later life. Many scientists regard muscle as the most important ‘organ of longevity’.

What’s this got to do with fasting?

Not only does eating protein and maximising muscle maintenance support a fasting practice: the reverse is also true. Fasting helps build and maintain muscle.


When we fast, we become more ‘anabolic’, meaning that we’re better at absorbing the protein we eat. It’s similar to the way we absorb protein more effectively after strength training.

That’s why a ‘bolus’ of 30g protein when you open your eating window is an important aspect of an optimal diet for fasting – because it can help kickstart muscle protein synthesis and prevent muscle loss.

Protein-rich break-the-fast meals in your optimal diet for fasting

Consider options such as a spinach and feta omelette with avocado, grilled salmon with roasted vegetables, or a tofu stir-fry. And check out my other blog posts for more recipes or follow me on LinkedIn where every week I post a new recipe which supports a diet for fasting.

You want to be eating balanced meals which prioritise fibre, protein, healthy fats, and complex carbohydrates to fuel your body and keep you satisfied until your next meal.

Eat 30 Different Plants Per Week

In addition to protein, an optimal diet for a fasting lifestyle includes 30 different plants per week.


Research has shown that – as well as fasting – consuming a diverse range of plants promotes a healthy gut microbiome, which is crucial for all-round health.

As Professor Tim Spector, global Gut Microbiome expert says, “Even if you feel perfectly normal, you can have poor gut health which is going to affect how long you live, how many chronic diseases you get, whether you get allergies, whether your immune system’s going to fight off Covid, your mood, your sleep, all things we hadn’t even thought were related”.

Gut microbes need a variety of minimally processed plants. Studies show that the sweet spot, on average, for producing the maximum number of species is 30 different plants per week, although there is some individual variation with some people doing better on more and some managing with fewer.

Embrace Healthy Fats

Another important component of an optimal diet for fasting is healthy fats.

Why is this?

Healthy fats – such as those found in extra virgin olive oil, avocados, nuts, fatty fish, and seeds – provide essential fatty acids (ie fatty acids the body can’t synthesize itself) which are necessary for brain health, healthy cell membranes, and the regulation of hormones and inflmmation.

They also steady blood glucose and provide satiety, which are important factors in an optimal diet for fasting.

Find your joy! – Creating a Sustainable Approach

Perhaps the most important aspect of optimising your diet for fasting is to enjoy your food!

If you don’t, you won’t sustain your healthy habits, whether that’s eating the right foods or eating them at the right time. And consistency is the key to all health habits.

Intermittent fasting is NOT supposed to be restrictive – you have a lot of food freedom within your eating window – and NOR is it supposed to be a quick fix.

It can and should be a flexible, forever lifestyle choice that allows you to savour delicious, nutrient-dense foods while super-charging your health and well-being.

Quick Round Up

By prioritising real, whole foods, minimising ultra-processed foods, and focusing on high-protein, meals which also contain a diverse range of plants, with some healthy fats thrown in, you can create a sustainable diet for fasting that nourishes your body and satisfies your taste buds.

Optimising your diet for fasting will massively enhance the benefits of intermittent fasting or longer fasts.

The beauty of a fasting lifestyle is that you’ll have the freedom to eat foods you love within your eating window, and you’ll become more attuned to your body’s hunger and fullness cues.

Liz Withyman

Liz Withyman is an ICF-registered ACC (Associate Certified Coach) who trained with the Coaches Training Institute, the most rigorous and respected coach training in the industry.

She runs her online Coached Intermittent Fasting Program, 7 Habits for a Vibrant Life, regularly throughout the year.

1:1 coaching is available on request. 

Become Part of
The Fasting for a Vibrant Life Community

Join the other women
who have made peace with food and are empowering themselves to get energy, clarity and be the weight they want to be through intermittent fasting. 

If you want to accelerate your journey to high-energy, vibrant health, join my 7 Habits for a Vibrant Life. You’ll get experiential coaching to work on your mindset, plain-English science in bite-sized chunks and my MicroHabits method to help you implement the healthy habits.

Did you enjoy this?
Here are other articles you may like

For how long should I fast?

For how long should I fast?

For how long should I fast? This is a question I am frequently asked and there is no simple answer, because it depends on your objectives. Different fasts achieve different results Here is a run down of the principle benefits from different fasting periods. Length...

Are you getting enough Zzzzzz for a Vibrant (& long) life?

Are you getting enough Zzzzzz for a Vibrant (& long) life?

In this blog I’m taking a look at some science around Habit # 4 of my Coached Intermittent Fasting program: SLEEP!  That most pleasant and fundamental bedrock of a Vibrant Life, which is hugely undervalued and under-prioritised in our society.  Not getting enough...

Fasting Fuel: Fantastic Fish pate with lime

Fasting Fuel: Fantastic Fish pate with lime

Principles behind my Fasting fuel series The food you choose for your eating window can either help or hinder your fasting practice. Choosing high fibre, high protein, high healthy fat foods made of real ingredients will support you to maintain the habit, because...

Join the Discussion


Submit a Comment

Your email address will not be published. Required fields are marked *