Intermittent fasting is currently one of the most popular nutrition programs around.
Unlike diets that tell you what to eat, intermittent fasting focuses on when to eat.
Limiting the hours you eat each day may help you consume fewer calories. It may also provide health benefits, including weight loss and improved heart health and blood sugar levels.
There are several forms of intermittent fasting, including a common form called time-restricted eating. This article tells you all you need to know about time-restricted eating.
Intermittent fasting is a broad term that refers to multiple specific eating patterns.
Each type of intermittent fasting includes fasting periods that are longer than a normal overnight fast of 8–12 hours ().
“Time-restricted eating,” or “time-restricted feeding,” refers to when eating is limited to a certain number of hours each day ().
An example of time-restricted eating is if you choose to eat all your food for the day in an 8-hour period, such as from 10 a.m. to 6 p.m.
The remaining 16 hours each day are the fasting period, during which no calories are consumed.
This same schedule would be repeated every day.
Summary: Time-restricted eating is a type of intermittent fasting that limits your food intake to a certain number of hours each day.
Many people eat from the time they wake up until the time they go to bed.
Switching from this style of eating to time-restricted eating may cause you to naturally eat less.
In fact, some research has shown that time-restricted eating can reduce the number of calories you eat in a day ().
One study found that when healthy adult men limited their eating to about a 10-hour window, it reduced the number of calories they ate each day by about 20% ().
Another study reported that young men ate about 650 fewer calories per day when they limited their food intake to a 4-hour period ().
However, other studies have shown that some people do not actually eat fewer calories during time-restricted eating (, ).
If you choose high-calorie foods during your feeding period, you may end up eating a normal day’s worth of food even though you are eating for a shorter period of time.
What’s more, most studies on time-restricted eating have used diet records to measure calorie intake. Diet records rely on participants to write down what and how much they eat.
Unfortunately, diet records are not very accurate ().
Because of this, researchers don’t know just how much time-restricted eating really changes calorie intake. Whether or not it actually decreases the amount of food eaten probably varies by individual.
Summary: For some people, time-restricted eating will reduce the number of calories they eat in a day. However, if you eat higher-calorie foods, you may not end up eating less with time-restricted eating.
Time-restricted eating may have several health benefits, including weight loss, better heart health and lower blood sugar levels.
Several studies of both normal-weight and overweight people restricted eating to a window of 7–12 hours, reporting weight loss of up to 5% over 2–4 weeks (, , , ).
However, other studies in normal-weight people have reported no weight loss with eating windows of similar duration (, ).
Whether or not you will experience weight loss with time-restricted eating probably depends on whether or not you manage to eat fewer calories within the eating period ().
If this style of eating helps you eat fewer calories each day, it can produce weight loss over time.
If this is not the case for you, time-restricted eating may not be your best bet for weight loss.
Several substances in your blood can affect your risk of heart disease, and one of these important substances is cholesterol.
“Bad” LDL cholesterol increases your risk of heart disease, while “good” HDL cholesterol decreases your risk ().
One study found that four weeks of time-restricted eating during an 8-hour window lowered “bad” LDL cholesterol by over 10% in both men and women ().
However, other research using a similar length of eating window did not show any benefits on cholesterol levels ().
Both studies used normal-weight adults, so the inconsistent results may be due to differences in weight loss.
When participants lost weight with time-restricted eating, their cholesterol improved. When they did not lose weight, it did not improve (, ).
Several studies have shown that slightly longer eating windows of 10–12 hours may also improve cholesterol.
In these studies, “bad” LDL cholesterol was reduced by up to 10–35% over four weeks in normal-weight people (, ).
The amount of glucose, or “sugar,” in your blood is important for your health. Having too much sugar in your blood can lead to diabetes and damage several parts of your body.
Overall, the effects of time-restricted eating on blood sugar are not entirely clear.
Several studies in normal-weight people have reported reductions in blood sugar of up to 30%, while a different study showed a 20% increase in blood sugar (, , ).
More research is needed to decide if time-restricted eating can improve blood sugar.
Summary: Some research shows that time-restricted eating may lead to weight loss, improve heart health and lower blood sugar. However, not all studies agree and more information is needed.
Time-restricted eating is very simple — simply choose a certain number of hours during which you will eat all your calories each day.
If you are using time-restricted eating to lose weight and improve your health, the number of hours you allow yourself to eat should be less than the number you typically allow.
For example, if you normally eat your first meal at 8 a.m. and keep eating until around 9 p.m., you eat all your food in a 13-hour window each day.
To use time-restricted eating, you would reduce this number. For example, you may want to choose to only eat during a window of 8–9 hours.
This essentially removes one or two of the meals or snacks you usually eat.
Unfortunately, there isn’t enough research on time-restricted eating to know which duration of eating window is best.
However, most people use windows of 6–10 hours each day.
Summary: Time-restricted eating is easy to do. You simply chose a period of time during which to eat all your calories each day. This period is usually 6–10 hours long.
If you exercise regularly, you may wonder how time-restricted eating will affect your workouts.
One eight-week study examined time-restricted eating in young men who followed a weight-training program.
It found that the men performing time-restricted eating were able to increase their strength just as much as the control group that ate normally ().
A similar study in adult men who weight trained compared time-restricted eating during an 8-hour eating window to a normal eating pattern.
It found that the men eating all of their calories in an 8-hour period each day lost about 15% of their body fat, while the control group did not lose any body fat ().
What’s more, both groups had similar improvements in strength and endurance.
Based on these studies, it appears that you can exercise and make good progress while following a time-restricted eating program.
However, research is needed in women and those performing an aerobic exercise like running or swimming.
Summary: Research shows that time-restricted eating does not negatively impact your ability to exercise and get stronger.
Time-restricted eating is a dietary strategy that focuses on when you eat, rather than what you eat.
By limiting all your daily food intake to a shorter period of time, it may be possible to eat less food and lose weight.
What’s more, some research has shown that time-restricted eating may benefit heart health and blood sugar, though not all studies agree.
Time-restricted eating isn’t for everyone, but it’s a popular dietary option that you may want to try for yourself.