What Is Intermittent Fasting?
Intermittent fasting (IF) is an eating pattern that cycles between periods of fasting and eating. Unlike traditional diets, it doesn't specify what to eat — it focuses on when to eat. The most researched mechanism is caloric restriction, but IF also triggers metabolic adaptations including reduced insulin levels, increased fat oxidation, and cellular repair processes called autophagy.
The Main IF Protocols
16:8 Method (Most Popular)
Fast for 16 hours, eat within an 8-hour window — for example, eating between 12pm and 8pm. Most people skip breakfast, which is manageable because the overnight fast already accounts for 7–9 hours. This is the most sustainable and widely studied protocol.
5:2 Diet
Eat normally for 5 days, restrict to 500–600 calories on 2 non-consecutive days per week. Popular in the UK following Dr Michael Mosley's research. Evidence shows comparable weight loss to continuous calorie restriction.
OMAD (One Meal a Day)
Eat all daily calories within a single 1–2 hour window. Very effective for weight loss but difficult to sustain and can make it hard to meet nutritional needs. Not recommended for most people without medical supervision.
Eat Stop Eat (24-hour fasts)
Complete 24-hour fasts once or twice per week. Can be effective but tends to cause significant hunger and may lead to overeating on non-fasting days.
Proven Benefits of Intermittent Fasting
- Weight loss: 0.5–1 kg per week when maintained consistently
- Improved insulin sensitivity: Fasting periods lower blood insulin, helping cells respond better to it
- Reduced inflammation: Studies show reductions in CRP and other inflammatory markers
- Better lipid profile: LDL cholesterol and triglycerides often improve
- Cellular autophagy: Fasting triggers cellular "clean-up" — clearing damaged proteins and organelles
- Simplicity: No calorie counting or food tracking required for many people
Who Should Avoid Intermittent Fasting
What Can You Eat and Drink During a Fast?
During the fasting window, the goal is to keep insulin levels low. Acceptable during fasting: water (still or sparkling), black coffee, plain green or herbal tea, black tea. Breaks the fast: anything containing calories — including milk or cream in coffee, diet drinks (controversial), and chewing gum.
Common Myths About Intermittent Fasting
Myth 1: "Skipping breakfast damages your metabolism"
The "breakfast is the most important meal" claim is largely unsupported. Metabolism does not slow with a brief overnight extended fast. What matters is total daily calorie intake, not timing.
Myth 2: "You'll lose muscle during fasting"
Short fasting periods (16–24 hours) do not cause significant muscle breakdown in healthy adults. Studies show muscle is preserved when protein intake is adequate and resistance training is maintained.
Myth 3: "IF is the same as starvation"
Starvation is involuntary and prolonged. IF is a structured, voluntary eating pattern with normal food intake within the eating window. The metabolic response is entirely different.