Intermittent fasting is more than the latest weight loss trend — it’s a path to better health and a more thoughtful relationship with food. 

While fasting is as old as humans, modern research suggests that intermittent fasting has many benefits, ranging from overall metabolic health to specific improvements in organs like the brain and heart.[1]

This short-and-sweet overview of fasting will explain:

• how fasting works;
• what the benefits of fasting are; and
• how to choose the approach that’s best for you. 

What is intermittent fasting?

Fasting simply means taking a break from eating — although you make sure to stay hydrated with calorie-free drinks like water, black coffee, or unsweetened black, green, or herbal tea. 

Intermittent fasting means doing this, well, intermittently. You abstain from food for a period of time and then eat normally. 

Typical intermittent fasting protocols include the following: 

• Time-restricted eating (TRE): Fast for several hours, most likely overnight, then enjoy an “eating window” of normal eating. There are many types of TRE schedules, such as:
  • 12:12 (12 hours fasting + 12 hours eating)
  • 14:10 (14 hours fasting + 10 hours eating)
  • 16:8 (16 hours fasting + 8 hours eating)
• 5:2: Eat normally five days per week, interspersed with two non-consecutive days of fasting. 
• Alternate day fasting (ADF): You’ll eat normally on day one, eat no more than 500 calories on day two, then repeat. 
• Eat Stop Eat: Eat normally through dinner on day one, abstain from food until dinner on day two, then repeat.

There’s no one way to do intermittent fasting, and there’s a fasting plan to fit everyone’s lifestyle. 

However, at Simple, we recommend time-restricted eating. 

It’s the safest and simplest option for most people, and most of our Simple users also like the convenience and flexibility of time-restricted eating.

How does fasting work?

Flipping the metabolic switch to fat burning

About 8–12 hours after your last meal, your body runs out of fuel and nutrients from that meal as well as whatever it’s stored in the liver. 

It needs to keep your body going, so it does something that scientists informally call “flipping the metabolic switch.”[2] 

With this switch, your body shifts from primarily using carbohydrate-based glycogen for energy to using stored fat from your fat tissues. This stored fat gets turned into substances called free fatty acids and then into ketones. 

Thus, you might know this state as being in ketosis.

This is a normal process that evolved to make sure our brain always has fuel, even if we have to go a little longer without food.

This metabolic shift is linked to many physiological changes that seem to have health benefits.[2]

You can see when your body switches to “fat-burning mode” by checking the Metabolic Status indicator in the Simple app while fasting.

What are the benefits of intermittent fasting?

We’ll take a closer look at the benefits of intermittent fasting in Article 1 of this guide, but here’s a quick list of the “greatest hits”:

Weight loss: Fasting usually means eating less overall, which can help people lose weight without feeling deprived or having to “go on a diet.” Longer periods of fasting and shorter eating windows (such as 16:8) seem to help the most.[3,4,5]

Metabolic health: Intermittent fasting improves many indicators of metabolic health, such as:[6,7,8]

• insulin sensitivity, or how responsive your cells are to insulin — which means better blood sugar management
• markers of heart health, such as blood pressure or better cholesterol levels

Brain health: Intermittent fasting is increasingly being studied for its effects on the brain, nervous system, and cognitive functions.[9] Many people report feeling more alert and focused while fasting. There is also some evidence that fasting may help slow neurodegeneration (i.e., a decline in brain or nervous system functions).

Mindful eating and hunger awareness: Many people find they’re more aware of their hunger cues when they fast, which helps them eat more intuitively. Fasting gives us an opportunity to experience being truly physically hungry and to appreciate nourishing our bodies when we do eat.

Learn more: the complete intermittent fasting guide

Inspired and want to learn more? Great! 

Check out each of these articles for a deep dive into various aspects of intermittent fasting. 

We hope this quick guide on intermittent fasting helps motivate you on your journey to better health. 

The more you know about intermittent fasting, the more likely you’ll be to stick with your fasting plan and see positive results. Enjoy!

11 intermittent fasting benefits

Intermittent fasting to lose weight

What to eat during intermittent fasting

What to drink during intermittent fasting

Intermittent fasting plans for beginners