The fasting period may last from 12 hours per day to several consecutive days, with a consistent, recurring pattern over the course of a week.
- modified fasting or the 5:2 diet — this protocol involves fasting for 2 non-consecutive days of the week, and eating normally for 5 days
- alternate-day fasting — fasting days are alternated with days where foods and beverages are consumed normally, without restrictions
- time-restricted eating — a type of intermittent fasting that limits the “eating window” to 4–12 hours, inducing a daily fasting period of 12–20 hours. Persons eat to satiety during their eating windows without caloric restrictions.
The 16:8 pattern — eating during an 8-hour window and fasting for 16 hours each day — may be the most recommended time-restricted eating pattern.
Much of the research on intermittent fasting and time-restricted eating considers the impact of fasting on the body’s natural circadian rhythm.
It is influenced by light and darkness over the course of the day, eating behaviors, and the timing of meals.
A growing body of
Thus, a major goal of fasting, specifically time-restricted eating, is to reduce the time spent eating in the day by extending the overnight fasting period.
The study of the relationship between circadian rhythms and food timing is called
Many of the benefits of intermittent fasting are attributed to daily fasting periods of no less than 12 hours, although some research suggests that a minimum of 16 hours of fasting may be required.
Here are some of the science-backed benefits of intermittent fasting.
1. Improved cholesterol levels
Findings across animal and human
Intermittent fasting has the
Elevated total cholesterol, LDL cholesterol, and triglyceride levels are
2. Blood sugar control
Intermittent fasting can improve
This results in
In fact, experimental research in adult males with type 2 diabetes showed the potential for intermittent fasting as a therapeutic approach that may reduce the need for insulin therapy.
3. Changes in body composition
Changes in body weight and
Several studies have shown that weight loss of between 3–7% body weight in an average of 8 weeks was achievable through intermittent fasting. Research also noted that this method could result in fat loss.
Fasting in a
Intermittent fasting can thus ease metabolic syndrome, a set of risk factors that increase the risk of heart disease and type 2 diabetes.
Despite the many touted benefits of intermittent fasting, there are also some downsides.
Intermittent fasting may be safe for heart and metabolic health, but according to a
- increased feelings of hunger
- heightened irritability
- worsened mood
- increased thoughts about food
- fears of feeling out of control around food
- overeating during eating windows
- difficulty concentrating.
Quality of evidence
Additionally, most of the research on intermittent fasting is based on animal research, with
This means that more rigorous human research on the long-term health benefits of intermittent fasting is warranted.
Intermittent fasting is not the only type of diet to result in the aforementioned benefits.
Some research suggests that the health outcomes of intermittent fasting are no greater than those observed in calorie restriction diets.
In fact, outcomes for weight and/ or fat loss, body fat percentage, and metabolic risk factors are
However, research on intermittent fasting shows a greater adherence over longer periods compared to calorie restriction, and suggests that it may be a more sustainable approach.
Like the potential
A major benefit of the Mediterranean diet compared to intermittent fasting is that similar results can be achieved without the need for fasting.
Intermittent fasting describes a variety of eating patterns that alternate periods of fasting and eating with a consistent, recurring pattern over the course of a week.
Time-restricted eating is the most popular form of intermittent fasting and uses the principles of chrono-nutrition to lengthen night-time fasting and potentially reduce chronic disease risk.
Intermittent fasting may improve cholesterol levels, blood sugar control, weight and/ or fat loss, lower inflammation, promote longevity, and support neurodegenerative conditions like Parkinson’s disease.
However, most of the research on intermittent fasting is based on animal studies and human research is sparse and often of low quality.
Alternative non-fasting diets that produce similar results to intermittent fasting include calorie restriction and the Mediterranean diet.