All these processes can benefit health. This brings up the question of whether the benefits of a calorie-restricted diet seen in animals may be a function not only of the reduced calorie content, but also of the time frame during which no food is consumed.

Is there an optimal way, researchers wondered, to incorporate fasting into a dietary regimen? What if instead of just cutting down on calories, attention were paid to when the meals that make up that restricted calorie diet are eaten? Several regimens have been proposed.

Eating a regular diet on 5 days and cutting calories down to on two days a week fast , doing the same on alternate days of the week fast , or fasting for hours a day daily time-restricted eating have all been tried.

In the latter case, no restrictions are placed on calories during the hours when food is consumed, but experiments have shown that this automatically results in a reduction of calories because night-time snacking is eliminated.

While most of the trials involving these regimens have resulted in weight loss, the benefits such as improvement in glucose regulation, blood pressure, inflammation, and loss of abdominal fat, go beyond what would be expected for weight reduction.

Over 6 months, both groups lost the same amount of weight, but the group had improved insulin sensitivity and a larger reduction in waist circumference. Some preliminary studies have also shown suppressed tumour growth in a number of cancers. There are even suggestions that intermittent fasting can improve memory and cognitive performance.

The evidence of benefits continues to accumulate. In a widely quoted study, one group of mice was given access to food only during a 9-hour period, while those in a control group were able to eat whenever they liked.

The two groups actually ended up eating roughly the same amount of food, so at least in this case, whatever results were obtained could not be ascribed to a difference in caloric intake.

After 7 weeks, tissue samples were taken from multiple organs and examined for any changes in gene expression.

Genes code for the production of proteins, so basically the researchers measured whether the production of various proteins increased or decreased. Genes that code for proteins responsible for inflammation were found to be less active, while genes that produce proteins that repair damage to DNA and ones that inhibit cancer cell survival geared up.

But, of course, mice are not men or women. So, what about men or women? One interesting study examined changes in a number of proteins produced as a result of eating only during a hour period and fasting for 14 hours. The subjects, 8 men and 6 women, were all observers of the Muslim religious month of Ramadan during which no food or drink is consumed between dawn and sunset.

These parameters are easily monitored and can provide information about the health effects of fasting in addition to changes in gene expression. All of the markers of metabolic syndrome shifted in the right direction during the month of the hour fast, as did proteins involved in destroying cancer cells, repairing DNA, and improving immune function.

All very interesting, but the experimental group was small and the study period of a month was short. Also, the subjects all had metabolic syndrome, and calorie intake was not considered. Basically, not much can be inferred as far as the general population goes.

That though is not the case for a study that compared the effects of eating an early or late dinner on glucose levels, insulin production, triglyceride levels and fatty acid oxidation which is a measure of ketosis.

Subjects ate their dinner either at 6 or 10 PM, and then had their blood chemistry monitored every hour through an intravenous line. The late dinner resulted in greater glucose intolerance and reduced fatty acid oxidation, both of which can promote obesity.

Why should this happen? During sleep, metabolism normally winds down since the body needs less energy. Therefore, ingested glucose and fats are not burned for energy, but rather end up being stored as fat. If dinner is eaten earlier, metabolism remains active until sleep time and less fat ends up being stored.

This study would seem to corroborate the benefits of the daily time-restricted fast since if no food is eaten after late afternoon, the reduced metabolism associated with sleep is less of an issue because most of the food will have been metabolized in the 5 or 6 hours between the last meal and sleep.

Now, just as I was ready to wrap things up with a final praise of intermittent fasting schemes, I learned of two recently published papers in respected journals. One found that in adults over the age of 40, a time interval of fewer than 4.

The second study asked participants to use an app to record the timing of their meals and then went on to relate this to their body weight as documented in their medical records over a ten-year period. Weight changes were not associated with the time between the first and last meals, which would seem to argue against trying to lose weight by time-restricted eating.

Where does all this leave us? As is the case with almost every aspect of nutrition there is controversy, and studies can be found to back up each side. Separating the wheat from the chaff is challenging and requires an extensive review of studies to try to get a handle on the preponderance of evidence.

Each type of intermittent fasting includes fasting periods that are longer than a normal overnight fast of 8—12 hours 1. 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.

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 2. Another study reported that young men ate about fewer calories per day when they limited their food intake to a 4-hour period 4.

However, other studies have shown that some people do not actually eat fewer calories during time-restricted eating 2 , 5. Diet records rely on participants to write down what and how much they eat. Unfortunately, diet records are not very accurate 6.

Whether or not it actually decreases the amount of food eaten probably varies by individual. Time-restricted eating may have several health benefits, including weight loss, better heart health and lower blood sugar levels. However, other studies in normal-weight people have reported no weight loss with eating windows of similar duration 2 , 9.

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.

However, other research using a similar length of eating window did not show any benefits on cholesterol levels 9. 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 8 , 9. Several studies have shown that slightly longer eating windows of 10—12 hours may also improve cholesterol.

Having too much sugar in your blood can lead to diabetes and damage several parts of your body. 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. and keep eating until around 9 p.

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. Because time-restricted eating focuses on when you eat rather than what you eat, it can also be combined with any type of diet, such as a low-carb diet or high-protein diet.

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.

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. 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. Make your journey into scheduled eating a little more manageable.

When you lose weight, your body responds by burning fewer calories, which is often referred to as starvation mode. This article investigates the…. Discover which diet is best for managing your diabetes. Getting enough fiber is crucial to overall gut health.

Let's look at some easy ways to get more into your diet:.

The observed improvements in heart health occured even when the TRE group did not lose weight, and they reported a lower desire to eat in the evening. Researchers need further studies done on more people over longer periods of time to confirm these findings.

Accumulating research suggests that TRE has potential, but not all studies show it is more effective for weight loss than daily regular calorie restriction. A review concluded that intermittent calorie restriction, including TRE, offers no significant advantage over limiting calorie intake each day.

More recently, a randomized controlled clinical trial in the New England Journal of Medicine showed TRE had no weight loss benefit after 12 months. In the trial, people with obesity followed TRE while also eating fewer calories or followed daily calorie restriction alone.

When the study ended, there were no differences between the groups for weight loss. Studies from and note that TRE results in equal weight loss to regular daily calorie restriction in people who are overweight or have obesity. Because of this, it is possible for TRE to be an option for people who want an alternate solution to daily calorie restriction for weight loss.

Other research does not show any benefit of TRE for weight loss compared with eating regularly throughout the day with no calorie restriction.

This includes when study participants receive no instruction to change their food choices or activity levels. As the science on TRE for weight loss advances, some researchers have expressed the need for caution around who might consider following TRE.

Among people who are overweight or have obesity, some studies have found that weight loss in TRE may be due to the loss of lean mass muscle versus fat mass adipose tissue. Therefore, it is especially important for people who are overweight or have obesity and who also have comorbidities such as sarcopenia to talk with a doctor before trying TRE.

The current evidence base shows promise for the role of TRE in weight loss in the short term from studies lasting less than 6 months. However, researchers need longer-term studies with larger numbers of more diverse participants to determine whether TRE can lead to clinically meaningful weight loss that a person can maintain over time.

A study from the journal Appetite aimed to look at the barriers to or facilitators of following TRE over the long term. It used 20 middle-aged adults who were overweight or had obesity and were at risk of type 2 diabetes.

The researchers assessed how easily people could incorporate TRE into daily life following a 3-month study with structured interviews. Seven study participants kept up with their instructions on TRE from the study, 10 adjusted their approach to follow a different version of their original instructions, and three did not follow through with their instructions.

Researchers need more work to understand how TRE influences the biological, behavioral, psychosocial, and environmental facilitators of and barriers to successful long-term weight maintenance.

One study investigated TRE in 11 adults who were overweight. They followed early-TRE for 4 days, where they ate between 8 a. and 2 p. and 8 p. The authors concluded that when participants followed the early-TRE plan, they had increased activity of mTOR.

This is a protein marker thought to be involved in maintaining muscle mass. A study, in the American Journal of Clinical Nutrition , randomly assigned 16 otherwise healthy males to follow early-TRE for 2 weeks or just regular calorie restriction.

It found the TRE group saw an improved ability for their muscle to use glucose and branched-chain amino acids. A study in Scientific Reports assigned 46 otherwise healthy older males to follow 6 weeks of either TRE or their regular eating plan. The TRE group had no significant changes in their muscle mass.

This suggests the participants kept their muscle throughout the study period. In studies that paired TRE with a structured resistance training program, muscle mass was maintained or small gains in muscle health occured:. The totality of evidence suggests that in combination with resistance training, TRE may improve body composition and help people maintain fat-free mass similarly to non-TRE plans.

Some researchers note that TRE may not be the best approach if primary health goals include building muscle mass and improving muscle strength because of the inconsistent eating frequency and nutrient availability for muscles.

However, TRE may be a good alternative for some people who are interested in changing their body composition or losing weight without it being problematic for maintaining muscle mass, growth, strength, performance, or endurance.

Researchers need additional longer and larger studies in different research settings with different populations to better understand the relationship between TRE and muscle health.

One of the main advantages of TRE is that it requires no special food or equipment. However, as with any eating plan, some thought and planning can increase the likelihood of success. The following tips can help to make TRE safer and more effective:. People should start with a shorter fasting period and then gradually increase it over time.

For example, start with a fasting period of p. to a. Then increase this by 30 minutes every 3 days to reach the desired fasting period.

Fruit fly hearts and human hearts are similar, so Panda believes it's reasonable to conclude humans might benefit in the same way. It's a positive feedback loop.

Panda hopes to continue his research, and find out whether the health benefits seen in animal studies hold true for humans. Data collected from his smartphone app, myCircadianClock, could be key.

The app helps people track when they eat, sleep, exercise and take supplements and medications. In most of Panda's studies, people eat their first meal between 8 a. and 10 a. but Charles Joy typically waits until 4 p. to break his fast. Joy's doctor initially was concerned by the diet, but Joy felt vindicated by his low cholesterol and blood pressure readings.

He has no plans to change things up anytime soon. American Heart Association News covers heart disease, stroke and related health issues. Not all views expressed in American Heart Association News stories reflect the official position of the American Heart Association.

Copyright is owned or held by the American Heart Association, Inc. Permission is granted, at no cost and without need for further request, for individuals, media outlets, and non-commercial education and awareness efforts to link to, quote, excerpt from or reprint these stories in any medium as long as no text is altered and proper attribution is made to American Heart Association News.

See full terms of use. These stories may not be used to promote or endorse a commercial product or service. Following an eating-fasting regimen might also be difficult for some people to maintain, especially if it interferes with their typical schedules, Gregg says. Time-restricted eating could also foster restrictive eating habits, so people with disordered eating should avoid it, Cederquist.

This approach can affect people differently and just might not work for everyone, she adds. I Tried the Carnivore Diet and It Broke Me. Pack on Size with These 9 Protein Pancake Recipes.

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