Intermittent fasting (sometimes called IF) is an eating pattern that involves periods of food restriction, called fasting, followed by a period of regular eating.

This pattern of eating could help you lose weight, reduce your risk of disease, and increase your lifespan ( 1 , 2 ).

Some experts even claim that its beneficial effects on metabolism make it a healthier way to lose weight than standard calorie restriction ( 3 ).

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Photography by Aya Brackett

Intermittent fasting is a simple,effective approach to fat lossthat’s relatively easy to stick to ( 4 ).

Studies have shown that when it comes to weight loss, intermittent fasting can be just as effective as traditional calorie restriction, if not more so ( 5 , 6 , 7 , 8 ).

In fact, a 2014 review found that intermittent fasting could help people lose an impressive 3–8% of their body weight in 3–24 weeks ( 9 ).

2016年的一项审查得出结论in people who have obesity or overweight, intermittent fasting may be a better approach to weight loss than very low calorie diets ( 10 ).

Interestingly, this approach to eating may also benefit your metabolism and metabolic health ( 1 , 11 , 12 , 13 ).

There are a很少有不同的方式to try intermittent fasting. Some people follow the5:2 diet, which involves fasting for 2 days per week. Others practice替代日禁食或者16/8方法。

如果您有兴趣尝试间歇性禁食，您可以阅读更多信息初学者的详细指南.

概括

Intermittent fasting is a powerful weight loss tool. It can also improve your metabolism and metabolic health.

Hormones are chemicals that act as messengers. They travel through your body to coordinate complicated functions, such as growth and metabolism.

They also play an important role in the regulation of your weight. This is because they have a strong influence on your appetite, the number of calories you eat, andhow much fatyou store or burn ( 14 ).

Intermittent fasting has been linked to improvements in the balance of some fat burning hormones. This could make it a helpful tool for weight management.

Insulin

胰岛素是参与脂肪代谢的主要激素之一。它告诉你的身体储存脂肪并阻止你的身体脱落。

慢性高水平的胰岛素可以使其更难以减肥。高水平的胰岛素也与肥胖等健康状况相关，2型糖尿病，心脏病和癌症（ 9 , 15 , 16 ).

Intermittent fasting has been shown to be just as effective as calorie-restricted diets forlowering your insulin levels( 17 , 18 , 19 ).

In fact, this eating style could reduce fasting insulin levels by 20–31% ( 9 ).

Human growth hormone

禁食会导致血液水平升高human growth hormone, an important hormone for promoting fat loss ( 20 , 21 ).

一些研究表明,男性水平的嗡嗡声an growth hormone may increase by as much as fivefold while fasting ( 22 , 23 ).

Increases in blood levels of human growth hormone not only promote fat burning, but they also preserve muscle mass and have other benefits ( 24 ).

但是，随着男性的努力，女性并不总是遇到与禁食相同的益处，目前尚未明确，如果女性会看到人类生长激素的同样升高。

Norepinephrine

Norepinephrine, a stress hormone that improves alertness and attention, is involved in the “fight or flight” response ( 25 ).

它对您的身体有各种其他影响，其中一个是讲述身体的脂肪细胞释放脂肪酸。

Increases in norepinephrine generally lead to larger amounts of fat being available for your body to burn.

Fasting leads to a rise in the amount of norepinephrine in your bloodstream ( 26 , 27 ).

概括

禁食可以有助于降低胰岛素水平，促进人生长激素和去甲肾上腺素的血液水平。这些变化可以帮助您更轻松地燃烧脂肪并帮助您减肥。

Many people believe that skipping meals will cause your body to adapt by lowering its metabolic rate to save energy.

It’s well established that very long periods without food can cause a drop in metabolism ( 28 , 29 ).

However, some older studies have shown that fasting for short periods can actuallyincrease your metabolism, not slow it down ( 30 , 31 ).

One older study in 11 healthy men found that a 3-day fast actually increased their metabolism by an impressive 14% ( 32 ).

这一增加被认为是由于激素去甲肾上腺素的兴起，这促进了脂肪燃烧。

Still, more high quality, recent studies are needed to evaluate how intermittent fasting may impact metabolism.

概括

Fasting for short periods can slightly boost your metabolism. However, fasting for long periods may have the opposite effect.

When you lose weight, your metabolic rate goes down. Part of this is because losing weight causes muscle loss, and muscle tissue burns calories around the clock.

然而，不能始终通过单独的肌肉肿块丧失（ 33 ).

Severe calorie restriction over a long period can cause your metabolic rate to drop, as your body enters so-calledstarvation mode. The scientific term for this is “adaptive thermogenesis.”

Your body does this to conserve energy as a natural defense against starvation ( 34 , 35 ).

This has been demonstrated dramatically in a study of people who lost large amounts of weight whileparticipating in “The Biggest Loser,”电视上的现实展示。

Participants followed a calorie-restricted diet and intense exercise regimen to lose large amounts of weight ( 36 ).

The study found that 6 years later, most of them had regained nearly all of the weight they had lost. However, their metabolic rates had not gone back up and remained around 500 calories lower than you would expect for their body size.

Other studies investigating the effects of calorie restriction on weight loss have found similar results. The drop in metabolism due to weight loss can amount to hundreds ofcaloriesper day ( 37 , 38 ).

This confirms that starvation mode is real and can partly explain why many people who lose weight end up regaining it.

Given the short-term effects of fasting on hormones, it’s possible that intermittent fasting may reduce the drop in metabolic rate caused by long-term calorie restriction.

However, currently there is no quality research available looking at the long-term effects of intermittent fasting diets on metabolic rate.

概括

One small study suggests that intermittent fasting may reduce the drop in metabolic rate that’s associated with weight loss. More research is needed.

肌肉是代谢活性组织，有助于保持您的代谢率高。这有助于你burn more calories, even at rest ( 39 , 40 ).

Unfortunately, most people lose both fat and muscle when they lose weight ( 41 ).

It’s been claimed that intermittent fasting could preserve muscle mass better than calorie restriction, due to its effect on fat burning hormones ( 42 ).

In particular, the increase in human growth hormone observed during fasting could help preserve muscle mass, even if you’re losing weight ( 43 ).

2011年的审查发现，在减肥期间留下肌肉的间歇禁食比传统的低卡路里饮食更有效（ 44 ).

However, results have been mixed. A more recent review found intermittent fasting and continuous calorie restriction to have similar effects on lean body mass ( 5 , 45 ).

最近的一项研究发现，在8周后，禁食和人们在连续卡路里限制上的人们之间没有区别。然而，在24周，禁食团体中的那些失去了瘦弱的体重（ 6 ).

需要更大且更长的研究，以发现间歇性禁食在保持瘦体重方面更有效。

概括

Intermittent fasting may help reduce the amount of muscle you lose when you lose weight. However, the research is mixed.

Although research has shown some promising findings, the effects of intermittent fasting on metabolism are still being investigated ( 3 ).

Early research suggests that short-term fasts boost metabolism as much as 14%, and several studies suggest that your muscle mass doesn’t decrease much with intermittent fasting ( 6 , 32 , 44 ).

If this is true, then intermittent fasting has several important weight loss advantages over diets based on continuous calorie restriction.

At the end of the day, intermittent fasting can be a highly effective减肥工具for many people.