From the Guidelines
The best intermittent fasting diet is the 16:8 method, where you fast for 16 hours and eat during an 8-hour window each day, as it provides significant metabolic benefits and is sustainable for most people. This approach typically involves skipping breakfast and eating between noon and 8 PM. Other effective options include the 5:2 diet (eating normally five days per week and restricting calories to 500-600 on two non-consecutive days) and alternate-day fasting, which have been shown to produce mild to moderate weight loss (3-8% loss from baseline) over short durations (8-12 weeks) with no significant differences in weight loss when compared with continuous calorie restriction 1.
To implement 16:8 fasting, start by delaying breakfast until noon and finishing dinner by 8 PM. Drink plenty of water, black coffee, or unsweetened tea during fasting periods to stay hydrated and help manage hunger. Begin with a 12-hour fast and gradually extend to 16 hours if needed. During eating windows, focus on nutrient-dense whole foods rather than processed items. Intermittent fasting works by triggering metabolic switching, where your body depletes glucose stores and begins burning fat for energy, potentially improving insulin sensitivity, cellular repair processes, and weight management.
Some studies have also explored the benefits of time-restricted eating, which involves limiting food intake to a specific window of time, such as 8-10 hours, and fasting for the remaining 14-16 hours 1. This approach has been shown to enhance fat loss, reduce oxidative stress, improve cardiovascular endpoints, and decrease glucose and insulin levels. However, the most recent and highest quality study on intermittent fasting, published in 2025, supports the 16:8 method as a effective and sustainable approach for weight loss and metabolic benefits 1.
People with certain medical conditions, such as diabetes, eating disorders, or pregnancy, should consult healthcare providers before starting any fasting regimen. It is also important to note that long-term follow-up and support from members of the diabetes care team are needed to optimize self-efficacy and maintain behavioral changes 1.
Key points to consider when implementing intermittent fasting include:
- Starting with a 12-hour fast and gradually extending to 16 hours if needed
- Drinking plenty of water, black coffee, or unsweetened tea during fasting periods
- Focusing on nutrient-dense whole foods during eating windows
- Avoiding processed items and added sugars
- Consulting healthcare providers before starting any fasting regimen, especially for people with certain medical conditions.
From the Research
Types of Intermittent Fasting Diets
- Alternate-day fasting: trials of 3 to 12 weeks in duration appear to be effective at reducing body weight (≈3%-7%), body fat (≈3-5.5 kg), total cholesterol (≈10%-21%), and triglycerides (≈14%-42%) in normal-weight, overweight, and obese humans 2
- Whole-day fasting: trials lasting 12 to 24 weeks also reduce body weight (≈3%-9%) and body fat, and favorably improve blood lipids (≈5%-20% reduction in total cholesterol and ≈17%-50% reduction in triglycerides) 2
- Time-restricted feeding: limiting the daily period of food intake to 8h or less has demonstrated efficacy for weight loss and improvements in multiple health indicators including insulin resistance and reductions in risk factors for cardiovascular disease 3
Health Benefits of Intermittent Fasting
- Weight loss: intermittent fasting has been linked to improvements in weight and metabolic outcomes 4
- Improvements in dyslipidemia and blood pressure: intermittent fasting regimens have favorable metabolic effects by intermittently inducing the metabolism of fatty acids to ketones 4
- Reductions in risk factors for cardiovascular disease: studies have demonstrated efficacy for weight loss and improvements in multiple health indicators including insulin resistance and reductions in risk factors for cardiovascular disease 3, 5
Comparison to Other Diets
- Intermittent fasting versus continuous energy restriction: randomized controlled clinical trials are required to establish the efficacy of intermittent fasting in improving general health, and preventing and managing major diseases of aging 3
- Intermittent fasting versus calorie restriction: the majority of trials have shown that intermittent fasting provides similar metabolic and weight benefits to calorie restriction, although a few suggest that intermittent fasting may be superior to calorie restriction 6