IntermittentFasting Guide.

No hype. Just the truth.

There's more nonsense talked about intermittent fasting than almost anything in fitness. People treat it like a magic switch. It isn't — but used properly it's one of the simplest, most freeing tools there is.

This is the guide Pete wishes everyone read before they tried fasting. No "metabolism hacks", no fasting supplements to buy, no pretending it's right for everyone. Just an honest, fifteen-page walk through what fasting is, why it works when it works, who it suits, who should leave it well alone, and exactly how to start without making yourself miserable.

• The real reason fasting works — and it's not magic (Chapter 2 will save you a lot of disappointment).
• Six protocols compared in one table — 12/12, 14/10, 16/8, 5:2, OMAD and the 24-hour fast — with Pete's honest pick for most people.
• A clear who-it-suits / who-should-skip-it checklist (this one matters — please read it).
• The four-week glide-in so you ease into it instead of crashing out by Thursday.
• Exactly what you can have during the fast — and the sneaky things that break it.
• The truth about fasted training and how to build your window around your sessions.
• A dedicated chapter on fasting for women — because the standard advice was written for men.
• Written by Pete — an 11× UK award-winning, 4× PT of the Year — not an influencer.

What's inside

Ten short chapters that take you from "should I even bother?" to knowing exactly how — and whether — to make fasting work for you.

You already fast every night — we just call it sleeping. Every day splits into a feeding window (when you eat) and a fasting window (when you don't). Intermittent fasting simply means making the fasting window a bit longer on purpose. You're not eating anything exotic; you're choosing when you eat, not what. The chapter also covers the single most useful lesson fasting teaches: hunger isn't an emergency, it's a wave that rises, peaks and passes.

The honest mechanism: shrinking the window in which you're allowed to eat means most people naturally eat fewer calories — and fewer calories over time is what loses fat. That's the engine; everything else is a passenger. The chapter sets your expectations straight so you don't fast all morning, eat 3,000 calories of pizza at night, and wrongly conclude "fasting doesn't work for me."

One table, six approaches, from gentle to hardcore: 12/12 (the beginner baseline), 14/10 (Pete's pick for most people), 16/8 (the famous one), 5:2 (two low days, five normal), OMAD (one meal a day — advanced) and the occasional 24-hour fast. Each with how it works, who it's best for, and a set of questions to help you choose the one you'll actually stick to.

Fasting is a tool, not a moral test. You'll likely love it if you're not hungry in the mornings, you're a grazer, or you prefer a couple of big satisfying meals. You should be cautious — or skip it entirely — if you have any history of disordered eating, you're pregnant or breastfeeding, you're a type-1 diabetic or on blood-sugar medication, or it simply makes you feel out of control around food.

The four-week glide-in: week one, just stop the late-night picking; week two, push breakfast back an hour; week three, drift towards 14/10; week four, only nudge towards 16/8 if it's easy. Plus the simple tricks that make the fasting hours painless — stay busy, front-load black coffee and water, never go to bed starving, and break your fast on protein, not pastry.

The "does this break my fast?" question, answered simply. For fat loss, only calories truly matter: water, black coffee and plain tea are fine; milk, sugar, juice and smoothies are not. The chapter also handles the grey areas — diet drinks, a splash of milk, BCAAs — and saves you from wasting money on "fasting supplements" you don't need.

Does fasted cardio burn more fat? Barely, and not in any way that matters over a full day. What matters far more is total calories and being able to train hard. The chapter gives you the honest take on fasted cardio and lifting, then the simple fix: build your eating window around your training, and always get protein in afterwards to protect your muscle.

When fasting "doesn't work", it's almost always one of these five: treating the window as a free-for-all, breaking the fast on junk, ignoring protein, going too hard too fast, and forgetting that bad sleep and high stress make any fast brutal. Avoid them and you're most of the way there.

This gets its own chapter because the standard "just do 16/8" advice was mostly written for men. Women tend to be more sensitive to longer fasts. The fix isn't to avoid fasting — plenty of women thrive on it — it's to be gentler and smarter: settle at 14/10, listen to your cycle, prioritise protein hard, and back off the moment sleep, mood or your cycle suffer.

Fasting is a tool, not a religion. If it gives you easier calorie control, more freedom and steady progress — keep going. If you've given it a fair go and it still makes you miserable or prone to bingeing, the strong move is to put it down and use one of the dozen other ways to get lean. The chapter ends on the five things that decide whether it lasts — and gives you full permission to quit if it's not serving you.

Common questions

© Pete Gawtry Fitness. The Intermittent Fasting Guide is free to download and share. This guide is general education, not medical advice — if you have a health condition, take medication, or are pregnant or breastfeeding, speak to your GP before fasting.