What Is Time-Restricted Eating?
TRE is the practice of eating all of your food within an eight to twelve-hour window during the day. The Salk Institute for Biological Studies’ Regulatory Biology Laboratory has found that fasting could be key to maintaining health.
The study found that the time of day that we eat may be more important than the food itself, especially in how it relates to the circadian rhythm.
The Salk Study
Despite eating the same diet, the mice in the first group became obese while the mice in the second group did not. Despite sharing many similarities, the mice in the first group became obese while the mice in the second group did not when they were both fed the same high-fat, high-sugar diet. This diet was similar to the standard American diet (SAD) consumed by many people. One group of mice had 24-hour access to food. The other group of mice was only able to eat during an eight-hour window at night, as mice are nocturnal animals.
The group who had access to the high-fat diet all day and night gained weight and developed health issues including high cholesterol, high blood glucose, liver damage, and diminished motor control after 100 days.
The group who had food available to them for eight hours weighed 28 percent less than the group who had food available to them at all times. Even though both groups of rats ate the same amount of food, the group with restricted eating times did not have the same health problems.
The researchers are confident that the results of this study in mice will be similar to what they would find in human studies. The researchers have done a few small human studies and the results have been good.
Dr. Satchin Panda, who led the study, said that the research suggests it may be better to eat at regular times and have set periods of fasting. The reason is that genes that control digestion are more active earlier in the day, while genes that control cellular repair are more active at night. It seems that eating food when the body is able to process it effectively may have some benefits for health.
TRE and body weight
Cienfuegos and his colleagues conducted a ten-week trial in which 58 adults with obesity were randomly assigned to one of two groups. The first group was given an eight-week intervention involving late TRE (where the TRE window is positioned later in the day). Adults were randomly assigned to one of three groups. The first group was allowed to eat whenever they wanted between 3 PM and 7 PM. The second group could eat whenever they wanted between 1 PM and 7 PM. The third group was the control group which didn’t have any special restrictions on when they could eat. Interestingly, weight loss was comparable between the intervention groups (~3%) after eight weeks versus controls. The stricter four-hour TRE did not result in greater weight loss compared to six-hour TRE. Approximately 30% reduction in energy consumption was achieved through both TRE regimens without participants having to monitor their calorie intake. The fact that participants reduced their energy intake when the eating period was shortened highlights the potential of TRE as a weight loss intervention.
Although TRE causes severe weight loss in the short term, it is not known if it is sustainable in the long term or if it affects nutrient absorption and long-term nutritional status. The focus of TRE research needs to be expanded to include studying its effects on dietary quality and biological processes. A study by Lowe et al. of 116 adults overweight or obese found that a late-TRE intervention resulted in a modest weight reduction of 1.17%. This was not statistically significant compared to controls.
When choosing when to have the TRE period, it is important to consider timing. Both Cienfuegos et al. and Lowe et al. instructed participants to refrain from eating the first meal of the day until the afternoon. A study has found that there is a correlation between consuming more calories later in the day and having a higher BMI and body fat percentage. Eating breakfast can help with weight management. The timing of the period of TRE may be just as important as the length of time it is restricted. Earlier TRE periods may be better because they are in line with people’s natural sleep cycles. This could lead to better results.
More research is needed to see if it’s better to do TRE earlier in the day for weight loss, with long-term clinical trials to assess if TRE is a good weight management intervention.
TRE and body composition
lrger losses of lean mass are found during weight loss interventions that involve high-protein diets. Appendicular lean mass, which includes muscle mass in the arms and legs, is associated with physical function and quality of life. The reduced appendicular lean mass may impair these things. The risk of weight gain is increased with this change in body composition.
Although protein intake was not measured, it’s possible that TRE led to an alteration in protein consumption. The authors also found that the TRE group had reduced physical activity levels, which could make the loss of lean mass worse. Whether TRE directly influences muscle loss is questionable. Therefore, more research is needed to explore the potential risk of TRE in individuals who are more likely to lose muscle mass, and whether changing the amount of protein and when it is consumed during the TRE period can reduce the loss of muscle mass.
Benefits of Time Restricted Eating
The thinking behind this type of eating is that it mirrors the typical eating habits of our forefathers. Hunter-gatherer societies didn’t always have food available to them. The animals may only have access to a meal twice a day when the prey is out and available to be hunted. It would make sense to replicate the eating habits of our ancestors as they didn’t have the same health issues we experience in modern society. TRE has been found to have many health benefits by researchers.
They found that if you keep eating, your body will keep storing fat. The body begins to burn fat for energy after a few hours of fasting. Time-restricted eating leads to reduced production of fat and improved utilization of fat in the body.
But the time we eat also helps. In an interview with Dr. Rhonda Patrick on YouTube, Dr. Panda explains that a study found that participants who ate lunch earlier in the day lost more weight than those who ate lunch later in the day. The study controlled for factors such as activity level and the types and number of calories consumed.
A review conducted at a later date found that in addition to reducing body fat, TRE also helps to reduce cholesterol and triglyceride levels.
The mechanism by which TRE produces weight loss is unclear; it may be due to the restriction of calories or to other factors. Eating unhealthy foods for late-night snacks is a bad idea, but it’s not as bad as eating those same foods earlier in the day.
Healthy Blood Sugar
TRE can also be helpful for balancing blood sugar. The continued eating habits cause the liver to produce glucose, leading to high blood sugar levels. Intermittent fasting or time-regulated eating is when you have long fasting periods, which gives your liver a break from producing glucose.
Additionally, during fasting times, glucose helps to build molecules that repair damaged cells and make new DNA. The Salk study found that when food was restricted to a 12-hour window, glucose tolerance, and insulin sensitivity were better.
The University of California San Diego conducted a study that found similar results. Over two thousand overweight women were divided into two groups. One group fasted for at least 12 hours straight while the other group fasted for a shorter amount of time. The group that fasted for at least 12 hours had blood sugar levels that were better than those of the group that fasted for shorter periods.
If you have blood sugar issues, you should eat small snacks regularly. This research suggests that longer periods of fasting may be beneficial, not shorter periods of fasting as suggested by prior advice.
The regulation of blood sugar and the use of glucose for cellular repair help to reduce inflammation. Chronic illnesses such as heart disease, cancer, stroke, and Alzheimer’s are caused by inflammation. The study found that the vaccine not only reduces inflammation but also leads to a healthier lipid profile and gene expression.
Reduced Metabolic Disease
The researchers of the Salk study looked further into the concept of TRE and found interesting results. The original study found that eating helps to regulate the body’s internal clock, but it is possible that the reverse is true. The findings suggest that the animal’s primary circadian clock may be to control when the animal eats. If the circadian clock is not functioning properly, chronic illness can occur. This illness may be a side effect of eating at the times when the body is least able to handle food.
The circadian clock naturally weakens as we age. This increase in the chances of metabolic illnesses parallels the increase in obesity rates. Researchers believe that by controlling the hours we eat, we can create a stronger circadian rhythm which may help prevent these illnesses. The findings are interesting considering that metabolic illnesses are increasingly common today.
The study found that the body only breaks down cholesterol into beneficial bile acids during fasting times. This breakdown helps cause the metabolism of brown fat. Brown fat is a type of fat that can be beneficial to health. It can help the body burn white fat, generate heat, and control blood sugar levels.
According to Dr. Panda, liver genes are more responsive to eating than to light. One study found that the genes of mice who were fed during the day were turned on and off at that time while the ones fed at night had their genes turned on and off at that time. It is important to eat regularly during the day in order to keep the liver working properly. Not eating at night is beneficial for allowing the liver to rest and repair itself. Because the study found that eating during the day can help protect against mild age-related fatty liver, it is believed that eating at night may have the opposite effect.
Acceptability and safety of TRE
Research into intermittent fasting has found that a high number of people drop out of studies, raising questions about how practical and acceptable the practice is. In contrast to this, Lowe et al. found that 83.5% of people stuck to a 12-week, eight-hour schedule of late TRE. When the TRE windows were more restrictive, the adherence rates were similar. The fact that the later eating periods are in line with traditional eating patterns suggests that the majority of the participants would be okay with scheduling dinner earlier in the day.
There were no reported negative consequences of TRE in the literature. Mild events such as headaches, diarrhea, increased thirst, and dizziness were potentially related to the intervention involving the release of tension from the erector spinae muscles, but occurred in the early stages and resolved by week three following adjustment to the intervention. However, people who are thinking about using TRE will need to be made aware of possible temporary effects to help them stick with it. There is a lack of research surrounding TRE, and most of what exists is done from a positivist perspective. However, there is some qualitative research that provides a different perspective and contributes to the overall evidence base.
Bjerre et al. used interview guides to examine the experiences and perspectives of participants who underwent TRE intervention. 17 people were recruited from a 12-week study that looked at the effects of 10 hours of TRE in adults who are overweight or obese. Many people said they were bored at night because they finished eating earlier. Reducing evening eating may help reduce obesity, but the reasons for eating at night are often more complex than just hunger. Emotions can play a role in night-time eating. TRE may inadvertently exacerbate existing vulnerability to overeating. In addition, some participants said they shifted the timing of when they ate certain foods, like candy, that they typically ate in the evening to earlier in the day. Others said they overeat at meals to stave off hunger they anticipate feeling when they’re fasting. It’s notable that participants realized they weren’t actually hungry and stopped overeating. The focus on when to eat did not elicit a focus on what was eaten, with many accommodating habitual food choices into the TRE window with no intention to change unhealthy dietary practices. This suggests that the timing of energy intake may be a more pressing issue for some people than the content of their diet.
TRE requires less cognitive restraint than calorie restriction, but participants found that they had to plan their daily routines more carefully. Some helpful strategies that people used were setting alarms as reminders and cooking enough food ahead of time so that they would have enough to eat even if something unexpected happened. The dietitian has an important role to play when patients are starting TRE, in terms of reducing the risk of emotional eating, helping them feel reassured about hunger, and providing guidance on healthy eating strategies.
The structured interviews at the end of the short crossover trial conducted by Parr et al. indicated that participants generally had positive experiences with TRE. Like Bjerre et al. found, doing things like eating out can be hard while following the TRE. This is because it can be tough to keep up with the TRE with all of the other things going on in life, and because of the social pressure to not follow the TRE. Eating later in the day may improve adherence, but this could have negative consequences from a metabolism perspective.