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Time-restricted Eating: 4 Critical Benefits for Health

time-restricted eating

By Jack Harley, MSc, University of Oxford 

We all know how important what we eat is for keeping healthy, but when you eat is also important. Time-restricted eating is a nutrition program that focuses on when you eat rather than what you eat. It involves limiting the period over which you eat during the day, and may help you consume fewer calories overall. 

What is time-restricted eating?

Time restricted eating is a nutrition program in which you restrict the timing of all your meals for the day within a 8-12 hour period. This leaves the remaining 12-16 hours of the day as a fasting period, in which no food is consumed.

People may adopt a time-restricted eating pattern for several reasons, such as to improve body composition, lose weight, sleep better or promote longevity. 

How to do time-restricted eating

Time-restricted eating is simple: choose a 8-12 hour window per day and eat all your meals within that period. If the goal is weight loss, the eating period should be less than your normal eating window. 

A popular method is the 16/8 method, in which you eat all of your meals of the day within an 8 hour period. This leaves a 16-hour fasting period each 24-hour cycle. For example, you could eat breakfast at 10 a.m., lunch at 2 p.m. and dinner at 6 p.m.. 

Alternatively, you could follow the 16/8 method by simply skipping breakfast and eating 2 or 3 meals between 12 noon and 8 p.m.. This similarly results in an 8-hour time-restricted eating pattern. 

It is not known what the ‘best’ time-restricted eating schedule is, as it is still a relatively new field of research. However, any 8-12 hour feeding period which is easy to maintain is probably most effective over the long-term.

Benefits of time-restricted eating

The many potential benefits of time-restricted include weight loss, improved cardiovascular health, and improved blood sugar levels. In addition, time-restricted eating may help to reset your circadian rhythm and help you live longer and healthier. 

Eating less

Most people consume calories from when they first wake up until they go to sleep at night. By limiting this ‘feeding’ window by following time-restricted eating, you may naturally eat less. 

In fact, some research has shown that time-restricted eating resulted in fewer calories being consumed overall. One study showed that men who followed a 10-hour time-restricted eating schedule consumed 20% fewer calories than those who ate freely. Another study showed that men who ate within a 4-hour period each day consumed 650 fewer calories per day than the control group. 

However, more research is needed to validate this finding, as other studies have demonstrated that time-restricted eating did not help to reduce the amount of calories consumed. One limitation of past research is that caloric intake is often estimated by dietary records which are self-reported, and may not always be accurate. 

Weight loss

Time-restricted eating may be effective in promoting weight loss, particularly in overweight or obese patients. 

Research by Dr. Satchin Panda from the Salk institute demonstrated that restricting food intake to a daily 8-hour window was associated with weight loss in obese patients. This 8-week long study showed that time-restricted eating resulted in a 3% reduction in body weight, compared to no change in body weight in the control group. Several other studies have also shown that time-restricted eating resulted in weight by 3% or more over a 1-month period. 

However, other studies have shown little to no weight loss from time-restricted eating, and so more research is needed. 

Therefore, the benefit of time-restricted eating for weight loss may depend on whether this eating pattern results in fewer calories being consumed. If you find that your daily energy intake per day is lower as a result of time-restricted eating, then it may be effective for weight loss. 

Cardiovascular health

The amount of ‘good’ (HDL) cholesterol and ‘bad’ (LDL) cholesterol in the blood can indicate your risk of heart disease. Research has shown that time-restricted eating may improve heart health by increasing ‘good’ cholesterol and lowering ‘bad’ cholesterol. 

One study found that 8-hour time restricted eating reduced levels of ‘bad’ cholesterol in the blood by 10% in 1 month. Other studies have shown that even 10-12 hour time-restricted eating can reduce ‘bad’ cholesterol levels by up to 35% over 1 month. 

However, other research has shown that a similar dietary pattern did not show a benefit to cholesterol levels. 

Metabolic health

Metabolism is the process by which the body converts food into energy. A time-restricted eating plan may improve metabolic health even if the total calories consumed remain the same. This is because time-restricted feeding may help to improve insulin sensitivity and blood sugar control. 

Some studies have shown time-restricted eating improved blood glucose and insulin response. This is important as it suggests that time-restricted feeding may help to reduce the risk of type 2 diabetes and other metabolic diseases.

One study showed that even when the total calories remained the same, eating within a 6-hour period was associated with decreased appetite and increased fat metabolism, compared to eating 3 meals across 12 hours. 

While time-restricted eating may help to improve blood glucose control and reduce markers of diabetes or pre-diabetes, more research is needed to validate this finding. 

Time-restricted eating and exercise

If you regularly exercise, you may be curious to know how time-restricted eating may influence weight loss and gains in strength and endurance. The available evidence suggests that the benefits of exercise are not reduced by a time-restricted eating schedule.

One 8-week trial showed that men following a time-restricted eating schedule gained just as much strength as those following a regular eating schedule. This suggests that time-restricted eating does not reduce strength improvements when following a workout program. 

Another 8-week study in men training showed that time-restricted eating resulted in a 15% loss of body fat compared to no fat loss in the control group who ate normally. In this study, both groups were performing weight training and saw similar improvements in strength and endurance. 

Time-restricted eating and longevity

Another benefit of time-restricted eating is that it may result in a longer and healthier life. In mice studies, micethat received one meal per day lived 11-14% longer than those that ate freely but consumed the same daily calories. This suggests that there is a metabolic benefit for longevity that is separate from simply restricting calories, which is known to extend lifespan in several animal species. However, more research is needed to verify whether the results of these animal studies will transfer to humans. 

Time-restricted eating and circadian rhythm

Circadian rhythm is the body’s 24-hour ‘biological clock’ that controls many important processes in the body. The most important of these is the sleep-wake cycle, which refers to the natural ebb and flow in sleepiness and awakeness during a 24-hour period. If you have ever experienced jet lag, you will be aware of the persistence of circadian rhythm. 

Following a time-restricted eating pattern may help to improve circadian rhythm. This is important for overall health, as a consistent circadian rhythm is important for getting high-quality, restorative sleep. 

How does circadian rhythm work?

Inside your cells and organs of the body are tiny biological ‘clocks’ that are synced to a master clock in the brain. This master clock responds to signals to tell the time, the most important being light. However, food is also a signal that the body uses to tell the time. For this reason, time-restricted eating may help to keep the biological clocks around the body synced to the ‘master’ clock in the brain.

Circadian rhythm and health

Circadian rhythms are closely tied to our body’s metabolism, and several metabolic processes such as appetite and energy expenditure occur in a cyclic way throughout a 24-hour cycle. 

When the circadian rhythm is disrupted, for example due to jet lag, shift work or irregular sleeping habits, this can negatively impact metabolism. However, eating within a consistent 8-12 hour period each day may help to ‘reset’ the biological clock and improve circadian rhythm.

A healthy circadian rhythm is important for getting proper sleep, and many cognitive functions such as learning and memory. On the other hand, an unhealthy circadian rhythm is associated with an increased risk of type 2 diabetes, mental illness and poor sleep. 

Therefore, research by Dr Satchin Panda at the Salk Institute and others demonstrating the benefit of time-restricted for maintaining circadian rhythm may be important for overall health.

What are other types of intermittent fasting?

Intermittent fasting is a broad term that describes nutrition programs that cycle between fasting and non-fasting periods. Time restricted eating is one type of intermittent fasting that follows a daily period of fasting. 

However, there are other types of intermittent fasting, which include: 

  • The 5:2 diet, in which you eat normally 5 days per week, but eat a reduced calorie diet on 2 days of the week
  • Eat Stop Eat diet, which involves one 24 hour fast each week.
  • Alternate-day fasting, in which you fast every second day. 

 

Conclusion

Time-restricted eating involves focusing on when you eat, rather than what you eat over a 24 hour period. By limiting food consumption to an 8-12 hour period, you may be able to lose weight by reducing calorie intake. In this way, time-restricted eating may help to combat weight gain and obesity. Even if you consume the same number of calories per day, you may still lose weight due to the beneficial effects of time-restricted feeding on metabolism. 

Some studies also suggest that time-restricted eating may improve heart health and blood sugar control. Additionally, time-restricted eating may also help to reset your circadian rhythm, resulting in better quality sleep. 

Time-restricted eating is a safe nutrition program, but always speak with your healthcare provider before altering your dietary practices. 

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