Intermittent fasting is an eating pattern that has become popular among people looking to lose weight.

Unlike diets and other weight loss programs, it doesn’t restrict your food choices or intake. Instead, all that matters is when you eat.

While some people claim that intermittent fasting can be a safe and healthy way to shed excess weight, others dismiss it as ineffective and unsustainable.

This article explains whether intermittent fasting works for weight loss.

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Intermittent fasting involves cycling between periods of eating and fasting.

Most types of this dietary pattern focus on limiting your meals and snacks to a specific time window — typically between 6 and 8 hours of the day.

For example, 16/8 intermittent fasting involves restricting food intake to just 8 hours per day and abstaining from eating during the remaining 16 hours.

Other types involve fasting for 24 hours once or twice per week or significantly cutting calorie intake a few days per week but eating normally during the others.

Although most people practice intermittent fasting to enhance weight loss, it has been associated with many other health benefits as well. In fact, studies show that intermittent fasting may improve blood sugar levels, decrease cholesterol, and boost longevity (1, 2).

Summary

Intermittent fasting is a popular eating pattern that restricts your food intake to a specific time window. It doesn’t limit the types or amount of food you eat.

Several studies show that intermittent fasting may boost weight loss via several mechanisms.

First, restricting your meals and snacks to a strict time window may naturally decrease your calorie intake, which can aid weight loss.

Intermittent fasting may also increase levels of norepinephrine, a hormone and neurotransmitter that can boost your metabolism to increase calorie burning throughout the day (3).

Furthermore, this eating pattern may reduce levels of insulin, a hormone involved in blood sugar management. Decreased levels can bump up fat burning to promote weight loss (4, 5).

Some research even shows that intermittent fasting can help your body retain muscle mass more effectively than calorie restriction, which may increase its appeal (6).

According to one review, intermittent fasting may reduce body weight by up to 8% and decrease body fat by up to 16% over 3–12 weeks (6).

Synergy with keto

When paired with the ketogenic diet, intermittent fasting can speed up ketosis and amplify weight loss.

The keto diet, which is very high in fats but low in carbs, is designed to kick-start ketosis.

Ketosis is a metabolic state that forces your body to burn fat for fuel instead of carbs. This occurs when your body is deprived of glucose, which is its main source of energy (7).

Combining intermittent fasting with the keto diet can help your body enter ketosis faster to maximize results. It can likewise mitigate some of the side effects that often occur when starting this diet, including the keto flu, which is characterized by nausea, headaches, and fatigue (8, 9).

Summary

Research indicates that intermittent fasting can increase weight loss by boosting fat burning and metabolism. When used in tandem with the ketogenic diet, it may help speed up ketosis to maximize weight loss.

Intermittent fasting has also been linked to several other health benefits. It may:

  • Improve heart health. Intermittent fasting has been shown to decrease levels of total and LDL (bad) cholesterol, as well as triglycerides, all of which are risk factors for heart disease (10, 11).
  • Support blood sugar control. A small study in 10 people with type 2 diabetes noted that intermittent fasting helped significantly decrease blood sugar levels (12).
  • Decrease inflammation. Several studies have found that this eating pattern may reduce specific blood markers of inflammation (13, 14).
  • Increase longevity. Although research in humans is lacking, some animal studies suggest that intermittent fasting may boost your lifespan and slow signs of aging (15, 16).
  • Protect brain function. Studies in mice reveal that this dietary pattern may improve brain function and combat conditions like Alzheimer’s disease (17, 18).
  • Increase human growth hormone. Intermittent fasting may naturally increase levels of human growth hormone (HGH), which can help improve body composition and metabolism (19, 20).
Summary

Intermittent fasting is associated with numerous health benefits, including decreased inflammation, increased heart and brain health, and better blood sugar control.

Most people can practice intermittent fasting safely as part of a healthy lifestyle. However, it may not be the best choice for everyone.

Children, individuals with a chronic illness, and women who are pregnant or breastfeeding should consult a healthcare professional before starting this dietary pattern to ensure that they’re getting the nutrients they need.

People with diabetes should also exercise caution, as fasting can lead to dangerous drops in blood sugar levels and may interfere with certain medications.

While athletes and those who are physically active can safely practice intermittent fasting, it’s best to plan meals and fast days around intense workouts to optimize physical performance.

Finally, this lifestyle pattern may not be as effective for women. In fact, human and animal studies indicate that intermittent fasting may negatively affect women’s blood sugar control, contribute to menstrual-cycle abnormalities, and decrease fertility (21, 22, 23).

Summary

Although intermittent fasting is generally safe and effective, it may not be right for everyone. Notably, some studies suggest that it could have several adverse effects in women.

Intermittent fasting has been shown to boost metabolism and fat burning while preserving lean body mass, all of which can aid weight loss.

When combined with other diets like the keto diet, it may also accelerate ketosis and reduce negative side effects, such as the keto flu.

Although it may not work for everyone, intermittent fasting can be a safe and effective weight loss method.