To lose weight through fasting, the duration and type of fasting vary depending on your goals, health status, and lifestyle. Here are the main points from current research and expert recommendations:
Intermittent Fasting (Shorter Fasts)
- 12 to 14 hours daily fasts : Fasting for 12 to 14 hours each day can encourage the body to burn fat stores for energy, promoting weight loss
- 16-hour fasts (16:8 method) : Commonly practiced by fasting for 16 hours and eating during an 8-hour window. Studies show young men fasting 16 hours lost fat while preserving muscle
. This method is popular because it extends overnight fasting and is easier to maintain
- Alternate-day fasting or 4:3 fasting : Involves fasting or severely restricting calories on some days and eating normally on others. One study found 4:3 intermittent fasting led to about 7.6% body weight loss over a year, outperforming daily calorie restriction
- Frequency : Daily intermittent fasting is most effective for weight loss, but some people fast 1-2 times per week or on alternate days depending on their schedule
Longer Fasts (Prolonged Fasting)
- 48-hour fasts : Fasting for 48 hours can provide benefits like weight loss, improved insulin sensitivity, and cellular repair, but should be done infrequently (1-2 times per month) and with caution
- 3-day fasts : Studies show fasting for three days can trigger significant weight loss (~5.7 kg lost in a study) and metabolic changes, but longer fasts (7 days) do not provide additional benefits
- 5-20 day fasts : Prolonged fasting for several days can cause clinically significant weight loss (2-10%), but much of the weight lost may include lean mass, and there are risks such as muscle loss and side effects like headaches and fatigue
Safety and Sustainability
- Intermittent fasting is generally safe for healthy individuals and can be easier to maintain than strict calorie counting
- Prolonged fasting should be medically supervised due to potential risks and side effects
- Extreme fasting (e.g., fasting without water or very long fasts) is not recommended.
- Weight lost during longer fasts may be regained if normal eating resumes without lifestyle changes
Summary Recommendation
- For most people aiming to lose weight safely and sustainably, starting with intermittent fasting methods like 12-16 hour daily fasts or 4:3 fasting is advisable.
- Longer fasts (48 hours or up to 3 days) can be done occasionally but require caution and proper hydration.
- Fasting beyond 3 days is generally not necessary for weight loss and carries more risks without added benefits.
Always consult a healthcare professional before starting any fasting regimen, especially if you have underlying health conditions. In essence, fasting for 12-16 hours daily or doing intermittent fasting several times a week is effective and safer for weight loss, while longer fasts should be approached carefully and less frequently
