Intermittent fasting is an eating pattern that alternates between eating and fasting periods. Intermittent fasting has various potential benefits, including weight loss and improved heart health.

Intermittent fasting restricts when or how much you eat — and sometimes both. One variation, time-restricted eating, involves eating only during a specific time window, usually eight hours, over a single day. For example, you would eat only from 11 a.m. to 7 p.m., then fast for the other 16 hours.

The other approaches, alternate-day and whole-day fasting, don't involve strict fasting. Instead, you choose two or more days during the week when you cut back on your food intake, limiting yourself to 400 to 600 calories daily. You follow your regular eating pattern on the other days of the week. In one popular version, the 5:2 diet, you eat normally for five days, then restrict your calories on two non-consecutive days. With alternate-day fasting, you eat a calorie-restricted diet every other day.

Intermittent fasting helps with weight loss.

A Harvard Medical School article shared that Intermittent fasting makes intuitive sense. Enzymes in our gut break down the food we eat, which eventually ends up as molecules in our bloodstream. Carbohydrates, particularly sugars and refined grains (think white flours and rice), are quickly broken down into sugar, which our cells use for energy. If our cells don't use it all, we store it in our fat cells. But sugar can only enter our cells with insulin, a hormone made in the pancreas. Insulin brings sugar into the fat cells and keeps it there.

As long as we don't snack between meals, our insulin levels will drop, and our fat cells can then release their stored sugar for energy. We lose weight when our insulin levels drop. The entire idea of IF is to let insulin levels drop far enough and for long enough that we burn off our fat.

Recent Studies about Fasting

Short-term studies suggest that some people stick to intermittent fasting diets better than others. According to a 2019 review article in the journal Nutrients, intermittent fasting promotes weight loss and may reduce risk factors for heart disease, including diabetes, high blood pressure, unhealthy lipid levels, and inflammation.

Flipping the switch from a fed to fasting state does more than help us burn calories and lose weight. The researchers combed through dozens of animal and human studies to explain how simple fasting improves metabolism and lowers blood sugar levels; lessens inflammation, which improves a range of health issues from arthritic pain to asthma; and even helps clear out toxins and damaged cells, which lowers the risk for cancer and enhances brain function.

There is some good scientific evidence suggesting that circadian rhythm fasting (Circadian Rhythm: the 24-hour internal clock in our brain), when combined with a healthy diet and lifestyle, can be an efficient approach to weight loss, especially for people at risk of diabetes. (However, people with advanced diabetes or who are on medications for diabetes, people with a history of eating disorders like anorexia and bulimia, and pregnant or breastfeeding women should not attempt intermittent fasting unless under the close supervision of a physician who can monitor them.)

4 ways to use this information for better health

Avoid sugars and refined grains. Instead, eat fruits, vegetables, beans, lentils, whole grains, lean proteins, and healthy fats (a sensible, plant-based, Mediterranean-style diet).
Let your body burn fat between meals, don't snack, be active throughout your day, and build muscle tone.
Consider a simple form of intermittent fasting. Limit the hours of the day when you eat, and for best effect, do it earlier in the day (between 7 a.m. and 3 p.m., or even 10-12 a.m. to 6 p.m., but definitely not in the evening before bed).
Avoid snacking or eating at nighttime, all the time.

Overall, studies indicate that intermittent fasting may be as effective as traditional calorie restriction for weight loss and body fat reduction. Evidence suggests that intermittent fasting may be easier to stick to than other conventional weight-loss methods. However, individuals should always discuss a new eating plan with a healthcare professional before starting.