Is time-restricted eating effective for weight loss?
A person on a time-restricted eating diet will only eat during specific hours of the day. Outside of this period, they will fast.
In this article, we look at what time-restricted eating is, whether or not it works, and what effect it has on muscle gain. We also provide beginner's tips on how to get started with this diet plan.
What is time-restricted eating?
Time-restricted eating involves eating only during specific timeframes.
Time-restricted eating means that a person eats all of their meals and snacks within a particular window of time each day. This timeframe can vary according to the person's preference and the plan they choose to follow. Typically though, the eating window in time-restricted programs ranges from 6–12 hours a day.
Outside of this period, a person consumes no calories. They should, however, drink water or no-calorie beverages to remain hydrated. In some time-restricted diet plans, people may also consume unsweetened coffee or tea with no cream.
Time-restricted eating is a type of intermittent fasting. Intermittent fasting refers to any diet that alternates between periods of restricting calories and eating normally.
Although time-restricted eating will not work for everyone, those who have their doctor's approval may find it beneficial. Some recent studies have shown that it can aid weight loss and may lower the risk of metabolic diseases, such as diabetes.
Time-restricted eating can help a person to restrict their food intake without having to count calories. It may also be a healthy way to avoid common diet pitfalls, such as late-night snacking. However, people with diabetes or other health issues should speak to their doctor before trying this type of diet.
Does time-restricted eating work?
No single diet plan will work for everyone. While some people are likely to have success with time-restricted eating, others may not benefit from it. It is best to speak to a doctor before trying time-restricted eating, or any other diet.
Many of the studies on time-restricted eating have been small or have involved animals rather than people, so large human studies are still necessary. Nonetheless, some recent research shows that time-restricted eating may have the potential to lead to weight loss and health improvement:
- In a study designed to mimic obesity in postmenopausal women, mice on a time-restricted feeding schedule lost weight and saw health improvements, unlike the mice that ate around the clock.
- Another study found that mice that only ate within an 8–9 hour period each day lost weight and had improved metabolic fitness.
- In one study, researchers allowed obese rats to eat for only 9 hours a day over the 5 weekdays. The young adult rats whose eating was time-restricted gained less weight than those that ate at any time. However, weight gain was the same in both groups of older adult rats.
- A small study found that time-restricted eating helped people with obesity to lower their calorie intake and lose a small amount of weight. The study limited eating to an 8-hour period and lasted for 12 weeks.
Although these studies suggest that time-restricted eating has potential, not all research shows a benefit.
A 2017 review concluded that intermittent calorie restriction, including time-restricted feeding, offers no significant advantage over limiting calorie intake each day.
Gaining muscle and time-restricted eating
Time-restricted eating may aid efforts to build muscle.
Research has shown that time-restricted eating can work well alongside efforts to build muscle.
One study investigated time-restricted eating in young men who followed a set resistance training program for 8 weeks. The men restricted their eating window to 4 hours on the 4 non-workout days each week.
The authors concluded that participants who followed the time-restricted eating plan reduced their calorie intake without losing strength. However, time-restricted eating did not result in reductions in body weight or body fat compared to a standard diet.
Another study placed resistance-trained men into either a time-restricted eating group or a normal diet group. Those in the time-restricted eating group ate 100 percent of their calorie needs during an 8-hour window each day for 8 weeks. The time-restricted eating led to a decrease in body fat with no reduction in muscle mass.
Beginner's guide to time-restricted eating
One of the main advantages of time-restricted eating is that it requires no special food or equipment. After getting a doctor's approval, a person can begin a time-restricted eating plan immediately.
However, as with any diet, some thought and planning can increase the likelihood of success. The following tips can help to make time-restricted eating safer and more effective:
Start with a shorter fasting period and then gradually increase it over time. For example, start with a fasting period of 10:00 p.m. to 6:30 a.m. Then increase this by 30 minutes every 3 days to reach the desired fasting period.
Studies have suggested that restricting feeding periods to less than 6 hours is unlikely to offer additional advantages over more extended feeding periods.
Exercising without overdoing it
It is tempting to start a vigorous exercise plan alongside a diet for faster results. However, with time-restricted eating, this could make the fasting period more difficult.
People may wish to keep their existing exercise program the same until their body adjusts to the new eating plan. This can help to avoid increased hunger from extra workouts, which could cause diet burnout or failure.
Focusing on protein and fiber
Hunger can be difficult for people who do not have experience of fasting for several hours each day. Choosing foods rich in fiber and protein during the eating window can help to combat this. These nutrients help a person feel full and can prevent a blood sugar crash or food cravings.
For example, eat whole-grain bread and pasta rather than white or refined grains. Choose a snack which includes protein in the form of lean meat, egg, tofu, or nuts.
Avoiding worrying about setbacks
Moving on from setbacks, rather than giving up on a diet, is important for meeting weight loss goals.
It is normal to have days where time-restricted eating does not work out. For example, a night out with friends, a special occasion, or a diet slip-up may lead to people eating outside of their fixed eating window.
However, this does not mean that they should quit.
It is best to see setbacks as an opportunity to get back on track. The next day, people can recommence the time-restricted eating plan and continue toward their goal.
For most people, time-restricted eating is unlikely to be a miracle weight-loss cure. However, studies have shown that it can offer health benefits without a high risk of side effects. It could be a simple way for many people to reduce their calorie intake without complicated or strict diet rules.
Which people, situations, or medical conditions might a time-restricted eating diet suit and why?
Time-restricted feeding seems to be beneficial for most people who are not experiencing acute illness or taking medications to lower blood sugar, for type 2 diabetes for example.
Adolescents, young adults, or middle-aged people may all benefit from time-restricted eating if they are only lightly or moderately physically active and are interested in:
- losing weight
- reducing blood sugar
- reducing gut inflammation or improving their gut microbiome
These people are most likely to experience benefits with minimal downsides.
Time-restricted feeding may also be beneficial for those who are not successful with daily calorie restriction since some study results indicate that both types of diet yield similar results.Natalie Butler, RD, LD Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.