What Is 16/8 Intermittent Fasting?
16/8 intermittent fasting means you fast for 16 hours and eat within an 8-hour window each day. Most people skip breakfast, eat their first meal at noon, and finish eating by 8 PM. No calorie counting required - just restrict when you eat, not what you eat.
It's the most popular fasting protocol because it's simple, flexible, and fits into any lifestyle. Research shows 16/8 leads to 3-8% weight loss over 8-24 weeks without tracking calories.
Unlike traditional diets that focus on what you eat, 16/8 focuses on when you eat. Learn more about meal timing.
People who want to lose fat without counting calories, busy professionals who skip breakfast naturally, late-night eaters who struggle with evening snacking, and anyone seeking metabolic benefits like improved insulin sensitivity.
Benefits of 16/8 Intermittent Fasting
Easier Fat Loss
By limiting eating to 8 hours, most people naturally eat 300-500 fewer calories daily. Studies show 16/8 leads to 3-8% weight loss over 8-24 weeks without tracking.
Better Appetite Control
Fasting stabilizes ghrelin (hunger hormone) and leptin (satiety hormone). After 2-3 weeks, most people report reduced hunger and fewer cravings.
Improved Insulin
16/8 lowers fasting insulin levels by 20-31% in as little as 8 weeks. This improves how your body processes carbs and reduces fat storage.
How Does 16/8 Intermittent Fasting Work?
No calories allowed. You can drink: water (still or sparkling), black coffee (no milk, sugar, or cream), plain tea (green, black, herbal), and zero-calorie electrolytes if needed.
Eat all your daily calories within this window. Most popular: 12:00 PM - 8:00 PM (skip breakfast), 1:00 PM - 9:00 PM (for later eaters), or 10:00 AM - 6:00 PM (early birds).
Milk or cream in coffee, BCAA supplements, fruit juice or diet soda (debated), bulletproof coffee (butter + MCT oil = calories), anything with calories even 5-10 calories.
How to Start 16/8 (Step-by-Step)
Week 1: Ease Into It (12/12)
Fast for 12 hours, eat for 12 hours. Example: Finish dinner at 8 PM, eat breakfast at 8 AM. This helps your body adapt without shock.
Week 2: Progress to 14/10
Fast for 14 hours, eat for 10 hours. Example: Finish dinner at 8 PM, eat first meal at 10 AM. You'll notice reduced morning hunger by now.
Week 3+: Full 16/8 Protocol
Fast for 16 hours, eat for 8 hours. Example: Finish dinner at 8 PM, eat first meal at 12 PM. Stick with this consistently for best results.
7 Common Mistakes Beginners Make
Eating Too Little
Just because you're fasting doesn't mean you should drastically cut calories. Aim for a 300-500 calorie deficit, not starvation.
Overeating in 8 Hours
"I fasted 16 hours, so I can eat whatever I want!" Wrong. If you eat 3,000 calories when maintenance is 2,000, you'll gain weight.
Drinking Calories
Lattes, protein shakes, or milk in coffee break your fast. Stick to water, black coffee, and plain tea only.
Training at wrong time without energy, not eating enough protein (aim for 1.6-2.2g/kg), ignoring electrolytes (causes headaches), and expecting overnight results (give it 4-6 weeks).
How to Train on 16/8 Fasting
Best Training Times
- Before eating window (fasted) - good for fat loss, cardio
- Mid-eating window (fed) - best for strength training
- End of eating window - allows post-workout meal
Avoid If Fasted
- Heavy HIIT or powerlifting as a beginner
- Training if you feel dizzy or weak
- Long endurance sessions without adaptation
16/8 Intermittent Fasting Results: Week by Week
Week 1: Adaptation Phase
Morning hunger, low energy, possible headaches. Your body is adjusting. Fat loss: Minimal (mostly water weight).
Weeks 2-3: Easier Appetite Control
Reduced morning hunger, more stable energy, fewer cravings. Hormones are stabilizing. Fat loss: 0.5-1 lb (0.2-0.45 kg) per week.
Weeks 4-6: Visible Results
Noticeable fat loss, improved mental clarity, better digestion. Fat loss: 4-8 lbs total (1.8-3.6 kg).
3 Months+: Strong Progress
Significant fat loss, established routine, lifestyle integration. Fat loss: 10-20 lbs (4.5-9 kg) total depending on adherence.
Pregnant or breastfeeding women, people with eating disorder history, diabetics (Type 1 or 2) without doctor approval, those with hypoglycemia, people under 18, and those who are extremely underweight.
A 2016 study by Moro et al. found that 8 weeks of 16/8 fasting led to significant fat loss while preserving muscle mass in resistance-trained men. Insulin sensitivity improved and inflammation markers decreased.