This week we will be discussing time restricted eating, what it means, and what it does for the menopause. Is there any evidence that time restricted eating will help during menopause? Does intermittent restricted feeding help with weight loss?
What is Time Restricted Eating?
Time restricted eating (TRE) is a diet involving periods of fasting and eating, for different periods of time. You may have heard of it in the news recently as it is primarily promoted as a weight loss diet.
TRE works on the basis that when the body is in a fasted state it will use glucose. This glucose is stored as glycogen in the muscles and liver for energy first. When glycogen stores become depleted, fat stores in the body will be used instead. This diet also puts you in an overall calorie deficit to further aid weight loss .
Types of Time Restricted Eating
Time-restricted eating (TRE) consolidates all calorie intake to 6-10 hour periods during the active phase of the day, without necessarily altering diet quality and quantity .
In addition, there are numerous types of TRE that are forms of intermittent fasting. The 5:2 diet is where you eat normally for 5 days a week then restrict calories to a quarter of your daily need for the remaining 2 days.
The 16:8 diet is the most common type of TRE that is promoted. This is where you fast for 16 hours per day and have an 8-hour eating window. This diet can also be adjusted to change eating and fasting windows.
Alternate day fasting is where you fast every other day, and eat stop eat is a 24-hour fast that is carried out once or twice a week. All these diets contain periods of eating and fasting. To learn more about intermittent fasting, read this blog post.
Are there any benefits of Time Restricted Eating?
TRE has been shown to have several health benefits in animal and human studies. Although, the number of human studies is limited. Many studies suggest that TRE provides beneficial metabolic effects, regardless of the degree of calorie restriction. A systematic review of 23 studies on TRE in adults found that the overall adherence rate to TRE was 80%, with a 20% unintentional reduction in caloric intake. TRE induced an average weight loss of 3% and a loss of fat mass .
Moro et al. reported that a combination of TRE 8/16 with regular physical activity reduced fat mass, decreased blood glucose levels, improved insulin resistance and lowered triglyceride levels .
Several studies have demonstrated the effectiveness of TRE as a weight loss method. One study showed that in 27 trials, weight loss of 0.8%–13% of baseline weight was observed, in obese and overweight participants . Furthermore, research into the effects of sex and menopausal status of the weight loss efficacy of alternate day fasting found no significant differences between premenopausal women, postmenopausal women, and men.
This study also found that fat mass, LDL cholesterol (bad cholesterol), fasting insulin, insulin resistance, and blood pressure decreased in both pre- and postmenopausal women. Suggesting that there are metabolic benefits of alternate day fasting, as well as weight loss .
In terms of TRE for blood glucose regulation, one study viewed the effects of TRE on blood glucose and insulin sensitivity in patients with type 2 diabetes. This study used a control group who ate a normal diet and a group of patients who tried TRE for 12 weeks. Both blood glucose and insulin sensitivity was improved in the TRE group, compared to the control group.
This study, like the previous study mentioned, found that levels of triglycerides, total cholesterol, and LDL cholesterol were improved in the TRE feeding group . A reduction in these factors can offer cardiovascular benefits and protect against things such as stroke, heart attacks, and heart disease .
TRE and sleep
Can TRE influence our sleep? In terms of sleep quality and TRE, limited studies have been carried out to support this reported benefit. One study, conducted in mice, found that TRE improve circadian rhythms when an 8-10 hour eating window was used. However, there is limited research proving this in humans .
Some studies have viewed the effects of TRE on sleep in humans when using an 4-6 hour eating window, in comparison to normal diet. They found that there were no benefits on sleep, and that sleep remained unchanged between the TRE group and control group .
TRE and gut health
The gut health of menopausal women is an area of interest because it has been linked to improved moods. One study found that in 30 healthy men, gut microbial composition and abundance was increased when following a high-fiber diet for four weeks .
Another study supported this finding and agreed that gut microbial richness was enhanced when following TRE. However, both studies were conducted with groups of men. Further research needs to be conducted to confirm that these effects are consistent across genders .
Finally, regarding cancer protective effects, there is also evidence suggesting that improvements in gut health caused by TRE may help to protect against colorectal cancer. Although, this study was conducted in mice so further research is needed to test effects in human participants .
Other types of cancer, such as breast and lung cancer have been studies in relation to TRE. They found that the calories restriction used in TRE had positive effects on both types of cancer. However, it is hard to determine if this is related to TRE or to the effects of weight loss [14, 15].
Time Restricted Eating and Menopause
There is limited research specifically about TRE and menopause. Research has been conducted in other forms of fasting such as alternate day fasting. Studies have shown the effects of sex and menopausal status of the weight loss efficacy of alternate day fasting do not differ between premenopausal women, postmenopausal women, and men [16,17].
An 8 week TRE study of pre-menopausal and post-menopausal women concluded that they lose similar amounts of weight (3.3%) during 8-weeks of TRE (4–6 h eating window). This study showed that fat mass, lean mass, fasting insulin, insulin resistance, and 8-isoprostane can be reduced after 8-weeks of TRE. However, other metabolic risk factors remained unchanged .
Risks of Time Restricted Eating
Although TRE is relatively safe. There can be a number of consequences including:
- feeling faint
- low energy
- sleep disturbances
There is also issues with people over-consuming on non-restricted days, leading to only minimal or no overall weight loss .
Additionally, a study comparing TRE and calorie restriction, a common weight loss technique, found that although mean weight loss was not significantly different between these methods, there was a higher dropout rate in the TRE group. This is a disadvantage of TRE as it is often an unsustainable method of weight loss, meaning that people often use it as a fad diet and regain the weight lost after stopping it .
There is evidence for multiple benefits of TRE, including anti-cancer effects, sleep changes, cardiovascular effects, and improved gut health. Research is limited, particularly in menopausal women to be able to draw clear conclusions. TRE may be an effective method of weight loss for some people. It is important to be aware of the un-sustainability of the diet. There is limited research on popular methods of TRE, therefore, any potential risks of these diets have not been identified yet. Decreasing your overall energy intake, and following a healthy, balanced diet, can see similar weight loss and metabolic effects as TRE.
Dietitian support for menopause
Sign up for my free newsletter and join my private Facebook Group for ‘nutrition and menopause’
Caroline Hill is a specialist menopause dietitian supporting women making dietary change. Caroline uses her extensive knowledge, skills and expertise of food and nutrition to help women manage their symptoms and weight during menopause. Caroline believes in providing sustainable, individualised, evidence-based advice to women making dietary change.