Time-restricted eating — also called fasting or intermittent fasting — is a time-honored tradition in many cultural practices. The method can also be used to cleanse the body, reset the metabolism, and help with weight loss. It can even help reverse or mitigate the symptoms of different health conditions. Is fasting right for you? Though some camps argue that fasting is little more than temporary starvation, research has shown the practice has numerous benefits. Proponents point out that time-restricted eating can kick-start your metabolism, give you more energy, and offer other health benefits minus the stress of counting calories or adhering to strict meal plans.

What is Fasting?

Fasting isn’t starving yourself, and neither is it simply refusing to eat. It’s not a diet, either. So, what is it? Fasting is refraining from drinking or eating for specific periods of time. In fact, most people fast at the end of every day, from after dinner until the morning. There’s a reason your first meal is called breakfast. Choosing to fast might be as simple as changing your eating schedule. Instead of eating the traditional three meals a day or “grazing” (eating numerous smaller meals throughout the day), fasting involves limiting food consumption to a specific window of time. Some people eat just once a day at a predetermined hour, and others may fast on predetermined days. Time-restricted fasting can help people incorporate a reduced-calorie diet over time.

Types of Fasting

Time-restricted eating usually involves abstaining from food for periods of 12-16 hours. This is also referred to as “intermittent fasting.” For example, you might choose to begin eating at 10 am, and stop at 8 pm. The interim is a fasting period, which includes sleep. Other types of fasting include alternate-day fasting: eating a small number of calories every other day, interspersed with days of normal food intake. The “warrior diet” involves eating fruits and vegetables primarily during the day, and having a well-balanced meal each evening. The right method for you depends on your size, gender, and health, and will ideally be advised by a doctor or nutritionist.

How Long Should You Fast?

The amount of time you fast depends on your personal preference and goals, in addition to the recommendation of a health professional. If you’re pursuing a spiritual fast, then you will adhere to the tenets of your faith. If you are fasting for improved athletic performance, then you might choose to eat less on your off days and more on your heavy workout days, especially if you are an endurance athlete who needs extra fuel. Finally, if you’re fasting for weight loss, then you might begin with intermittent fasting, which allows you to eat to satiety but limits when you can eat, helping you reduce calories without feeling deprived. If you’re new to fasting, you may want to start with a short-term fast and increase the time between meals if you’re able to do so.

Menu Planning for a Fast

Before you fast, decide when you will be eating and what you plan to eat. Having your meals planned out, and even prepared ahead of time, can help prevent lapses and snacking. Determine a healthy balance of carbohydrates, dietary fats, and protein, so you can meet your nutritional needs (which will also help prevent snacking). Choosing to stock your fridge with healthy, ready-to-eat foods like cut fruit and vegetables or portioned servings of nuts, can help you acclimate to the fasting period. That way, if you must have a snack, there is something low-calorie waiting for you. Listen to your body’s needs, and if you feel lightheaded or cranky, eat a snack. It’s ok to ease into fasting.

Health Benefits of Fasting

There are a few health benefits to fasting. Several studies indicate regular fasting can slow the aging process by reducing inflammation of tissues and decreasing body weight. In animal studies, mice on regular fasting schedule lived longer than their counterparts who ate more frequent meals. Fasting can also help lower the HDL or “bad” cholesterol in the bloodstream. Intermittent fasting helps lower triglyceride levels and decreases your risk of heart disease and stroke. Also, fasting stabilizes LDL or “good” cholesterol levels. Improved ratios of LDL and HDL cholesterol, in turn, improve cardiovascular health.

Do Liquids Count When Fasting?

Most experts recommend refraining from alcohol while fasting, but drinking water is encouraged. Aside from that, the kinds of liquids that you consume depend on your fasting goals. If you’re choosing to reduce calories, then drinking beverages high in calories, such as milk or coffee drinks, might detract from your end goal. For those practicing time-restricted, or intermittent fasts, no- or low-calorie drinks like water, black coffee, and hot or iced tea are your best bets during the fasting windows. If you’re on an alternate day diet or something similar, most guidelines allow for drinking various beverages during low-calorie hours. Consider your calorie goals carefully, as well as the nutrients your body needs. It’s not advisable to fill up with liquids when you only have a brief window of time to eat your nutrients.

Can I Excercise While Fasting?

Have a doctor evaluate your fasting practices and physical activity. If you are training for an endurance event, fasting might not fuel your training. However, you can usually exercise while fasting. In fact, many people report better success with “fasted cardio”; that is, doing cardio exercise before breaking their fast. Morning workouts might benefit those who practice time-restricted fasts, as they might have more energy to work out without a full belly. On low-calorie days, you might not have the energy for a high-impact workout. A short walk or gentle yoga class can boost your energy levels without overtaxing your system.

Can Fasting Aid Weight Loss?

Weight loss depends on consuming fewer calories than your body requires. Fasting can help you reduce your caloric intake by limiting when you can eat. There have been several studies that support fasting as an excellent tool for weight loss. By allowing you to have periods when they can eat as you choose, many dieters report that it’s easier to stick to a caloric deficit without feeling deprived. A study of five-day fasts, where subjects eat between 700 and 1100 calories, with the greater number of calories on the two off days, had other benefits. These fasters demonstrated reduced inflammation levels and trimmed their waistlines and lost total body fat without sacrificing muscle mass.

Can Fasting Improve Athletic Performance?

Athletic performance may be improved by fasting at certain times. Fasting can be a fat-burner because your body uses stored fat for energy instead of glycogen from the food you eat. A lower body fat percentage makes a difference for both professional and amateur athletes. Fasting can also effectively optimize muscle growth and can increase the production of human growth hormone (HGH), which can help you both build muscle and increase muscle strength. HGH is produced naturally in the body, but only active for brief periods of time.

Can Fasting Help Metabolic Disorders?

Metabolic syndrome, pre-diabetes, and type 2 diabetes are consequences of reduced insulin sensitivity in your cells. This happens when your body has excess glucose from too many carbs and sugars. Fasting can reduce the amount of glucose in your bloodstream. Intermittent fasting can help reduce the amount of visceral fat in your body, which can decrease diabetes markers. It also helps regulate the production of ghrelin, the “hunger hormone,” and curbs cravings for carbs and sugar. By retraining your body about when to secrete ghrelin, you can better control the number of excess sugars you’re eating, and reduce your insulin resistance.