Intermittent fasting (IF) has solid evidence for type 2 diabetes — and serious cautions for people on diabetes medications.
The protocols
### 16:8 (most common) Eat within an 8-hour window, fast for 16. Example: eat 12–8 PM, fast 8 PM–12 PM next day.
### 14:10 (gentler entry point) Eat within 10 hours. Easier for beginners.
### 5:2 Eat normally 5 days, eat ~500 calories for 2 non-consecutive days.
### OMAD (one meal a day) 20-hour fast, single large meal. Aggressive — not for everyone.
What the evidence shows
- 16:8 improves HbA1c by 0.4–0.7% in 3-month trials
- Reduces fasting insulin, often more than glucose
- Improves weight loss when combined with sensible eating
- 5:2 shows similar HbA1c results
Why it works
- Lowers insulin during fasting windows, increasing sensitivity
- Often spontaneously reduces calorie intake by 200–500/day
- Liver gets time to clear stored fat
- Improves circadian rhythm
Cautions
### Don't fast if you take: - Insulin (without dose adjustment from your doctor) - Sulfonylureas (glipizide, glyburide) - Meglitinides
### Don't fast if you have: - Type 1 diabetes (high DKA risk) - History of eating disorders - Pregnancy or breastfeeding - Active cancer treatment - Low body weight
Starter plan for type 2
Week 1: 12-hour overnight fast (8 PM to 8 AM) Week 2: 14-hour fast Week 3+: 16:8 if comfortable
Monitor glucose, especially in the first 2 weeks. Hydrate aggressively. Stop if you feel lightheaded, confused, or shaky.