What can I consume during the fasting window?

Water, black coffee, plain tea, and sparkling water. Anything with calories breaks the fast. Black coffee has no meaningful caloric content.

Should I train fasted or fed?

Both work. For strength training, performance is better when fed. For cardio, fasted is fine for most individuals.

Does intermittent fasting slow metabolism?

Short-term fasting (16–24 hours) does not slow metabolism. Prolonged calorie restriction causes metabolic adaptation, but this occurs with any calorie deficit, not specifically IF.

What is the best IF schedule for beginners?

16:8 is universally recommended: fast from 8pm to 12pm, eat between 12pm and 8pm. Most studied, most flexible.

Nutrition

Intermittent Fasting: What It Is, How It Works, and What Schedule to Choose

📅 March 16, 2026⏱ 7 min read🏷 Fat Loss · Nutrition

Intermittent fasting (IF) is an eating pattern that cycles between periods of eating and voluntary fasting. It has become one of the most popular dietary strategies for fat loss and metabolic health — but which protocol is right for you depends on your lifestyle, goals, and training schedule.

The Most Popular IF Protocols

Protocol	Eating Window	Fast Duration	Best For
16:8	8 hours	16 hours	General fat loss, easiest to sustain
18:6	6 hours	18 hours	Greater calorie restriction, moderate adherence
20:4 (Warrior Diet)	4 hours	20 hours	Aggressive fat loss, difficult to sustain
5:2	Normal 5 days	500–600 kcal on 2 days	Flexibility lovers, non-consecutive fast days
OMAD (1 meal/day)	1–2 hours	22–23 hours	Extreme restriction, low adherence

Does Intermittent Fasting Work for Fat Loss?

Yes — but primarily because it helps create a calorie deficit, not because of any special metabolic mechanism. A 2020 review in New England Journal of Medicine found that IF produces fat loss equivalent to continuous calorie restriction when total calories are matched. The advantage of IF is behavioural: many people find it easier to skip meals than to count calories.

💡 IF does not give you a "metabolic advantage." Its power is making it easier to sustain a calorie deficit by compressing your eating window and naturally reducing opportunities to eat.

Intermittent Fasting and Muscle Mass

Concern: Does fasting break down muscle? Short-term fasting does not cause significant muscle loss in healthy, trained individuals with adequate protein intake. The key variables are total daily protein (hit your target within your eating window) and resistance training (continue lifting — the anabolic signal of training preserves muscle during fasted periods).

Longer fasts (24–72 hours) begin to increase muscle protein breakdown rates, which is why extended fasts are not recommended for individuals focused on muscle retention.

Who Should Not Do Intermittent Fasting

People with a history of eating disorders
Pregnant or breastfeeding women
Type 1 diabetics or those on insulin who need stable meal timing
Those with very high training volumes who cannot meet calorie needs in a compressed window

How to Choose Your Protocol

Start with 16:8 — it is the most studied, most sustainable, and easiest to implement around social life. Skip breakfast, eat your first meal at noon, finish eating by 8pm. Adjust the window based on your schedule and hunger patterns. If 16:8 is not producing results after 4–6 weeks, tighten to 18:6.

Find Your Ideal Fasting Schedule

Get a personalised fasting and eating window based on your lifestyle and goals.

Use the Intermittent Fasting Calculator →

Frequently Asked Questions

Water, black coffee, plain tea, and sparkling water. Anything with calories (including milk, cream, sweetened drinks, gum with significant caloric content) technically breaks the fast. Black coffee has no meaningful caloric content and does not impair IF benefits.

Both work. Fasted training can slightly increase fat oxidation. Fed training often allows higher intensity. For strength training, most evidence suggests performance is better when fed. For cardio, fasted is fine for most individuals.

Short-term fasting (16–24 hours) does not slow metabolism — some studies show a slight increase in metabolic rate due to norepinephrine release. Prolonged calorie restriction (weeks to months) does cause metabolic adaptation, but this occurs with any calorie deficit, not specifically IF.

16:8 is universally recommended for beginners: fast from 8pm to 12pm (skipping breakfast), eat between 12pm and 8pm. It is the most studied, most flexible, and compatible with most social schedules.

← Body Fat Methods Squat Standards →