Intermittent fasting doesn't dictate what you eat — only when. Here's the complete evidence-based guide to the most popular dietary strategy of the decade.
How IF Produces Weight Loss
Primarily through natural calorie reduction — a narrower eating window means fewer calories consumed without deliberate counting. Additional benefits include improved insulin sensitivity, increased fat oxidation during fasting, elevated noradrenaline (fat mobilisation), and autophagy during extended fasts.
The Main Protocols
16:8 — Most Popular
Fast 16 hours, eat within 8 hours. Most common: skip breakfast, eat noon-8pm. A 2022 NEJM trial found 16:8 produced comparable weight loss to daily calorie restriction — but many find the time restriction easier than counting calories daily.
5:2 (Michael Mosley Method)
Normal eating 5 days; 500 calories on 2 non-consecutive days. The original "Fast Diet." Good for people who struggle with daily restriction but can tolerate 2 severe restriction days.
OMAD (One Meal a Day)
All calories in one meal. 23:1 fasting ratio. Effective but challenging to meet nutritional needs in one sitting. Not recommended for sustained long-term use.
Alternate Day Fasting
Alternates normal eating with ~500-calorie days. Produces 5-8 lbs more loss than continuous restriction in some trials but significant adherence challenges.
Who Should NOT Try IF
Pregnant/breastfeeding women · eating disorder history · type 1 diabetes · underweight individuals · children and adolescents · medication requiring food
Starting 16:8
Week 1: Push breakfast back 1 hour. Week 2: Another hour. Continue until eating noon-8pm. Black coffee, plain tea, and water are allowed during fasting hours. Add electrolytes if you get headaches in the first 2 weeks.