Time-Restricted Diet

“No diet or exercise, get a slim body in 3 months without spending a dime!” This is not a false weight loss advertisement, but the results of a time-limited diet study recently published in the journal Cell-Metabolism. The journal is authoritative and the results are tantalizing, but immediately using this method to lose weight, you’re in too much of a hurry.
This new trick called a time-restricted diet means that you are only allowed to eat and drink for a certain number of hours each day, and fast at other times (water without energy is allowed). There are no restrictions on what and how much you can eat during the time you are allowed to eat.

For example, a 10-hour eating restriction: breakfast at 9:00 a.m., whatever you want between meals, but the last meal by 19:00 a.m., and then no food until breakfast the next day. Another term that has become popular in recent years is “intermittent fasting”, and time-restricted diets are a type of intermittent fasting. Since studies have shown that intermittent fasting is effective in short-term weight loss and also improves blood lipids and blood glucose, people are looking forward to time-restricted diets.

The study was conducted in California, USA, with 19 (13 of them male) participants who all had metabolic syndrome and usually ate for at least 14 hours a day.

To participate, download a smartphone app called “myCircadianClock”, follow the instructions to limit your eating to 10 hours a day, and record what you eat.The time-restricted diet is much simpler to follow than the complicated weighing and measuring of food when restricting total energy.

Not only is it easy to follow, but a time-restricted diet is also easier to stick to than a diet and exercise.The vast majority of participants in the study were able to follow the diet for 3 months without serious discomfort, and after 3 months, not only did the participants lose an average of 3.3 kilograms, but they also reduced their body fat percentage and waist circumference (waist circumference was reduced by an average of 4.5 centimeters).This rate of weight loss was comparable to the effect of abstinence plus exercise.At the same time participants had lower blood pressure and blood lipids and a slight improvement in blood glucose.

The results were so good that most people spontaneously continued the time-restricted diet after the study ended.Until more than a year later, a quarter of the people still adhered to the daily time-restricted diet.

As good as the results are, the conclusions of one study alone are not convincing enough.Time-restricted diets have recently been supported by the results of other studies: a 3-month time-restricted diet can significantly reduce weight and waist circumference in overweight and obese people, without increasing exercise.

Even if short-term weight loss works, you still have to be able to stick to it for the long term to make sense.Regarding the ease of adhering to a time-restricted diet, 40% of the participants found it easy to adhere to, while only 10% found it difficult. Most obese individuals can adhere to time-restricted diets as low as 8 hours, and sleep and poor eating behaviors improve rather than worsen.

Long-term dieting can easily lead to malnutrition, but when people go on time-restricted diets, they don’t reduce the amount of healthy foods such as vegetables and fruits they eat, they just reduce the amount of snacks they eat.Not only did they eat healthier, but some people’s blood pressure, blood lipids and blood sugar levels also improved during time-restricted diets.

Some people are concerned that prolonged fasting will result in muscle loss. Studies have shown that short-term time-restricted diets for men who are regular amateur strength trainers do not result in a decrease in muscle size or strength.

Do time-restricted diets work so well just because you eat less or is there something else going on?

In terms of total dietary energy, although these studies did not restrict food composition or quantity, because the window in which you can eat is shortened, you can’t eat as much until you are full.Changing from an unrestricted diet to a time-restricted diet can reduce energy intake by hundreds of kilocalories per person per day on average.In addition, most people usually like to eat fattening snacks in the evening, time restriction reduces the opportunity to eat these snacks, but also conducive to weight loss.

In addition to energy and composition, the time you eat also affects your weight.Many people have a “bird’s stomach for meals, but not for snacks”, and only give their stomachs a short break in the early hours of the morning before bedtime and until 6 or 7 am. This long-lasting and irregular eating habit can affect the body’s biological clock (circadian rhythm).

The human biological clock in the brain is not only regulated by light, but diet is also an important influence. Eating and fasting time for a long time with the biological clock does not match, will interfere with the biological clock and affect the endocrine, autonomic nervous system and nutrient metabolism and other balances, increasing the risk of obesity and “three highs”!

Time-restricted diets may make eating and sleeping times more regular and stop late-night eating.A better biological clock facilitates weight loss, and some people sleep better as a result, and their overall health improves.

Since time-limited diets are so simple and effective, wouldn’t it be better to download a mobile app right away and sit back and wait to get thinner? Wait a moment.

1 Weight loss is not always possible

First, while most time-limited diet studies have promising results, the small total number of relevant studies and the small number of participants in each study make the conclusions not necessarily reliable.

Second, some of the studies did not have a control group, and participants may have been embarrassed to eat so much unhealthy food because they knew they were participating in a diet-related study (the cueing effect caused by the unrestricted, app-only downloads and logging of diets may have also been weight loss).

On the participant side, most studies with substantial weight loss results have targeted overweight and obese populations.One study showed that when enrolling recently weight-stabilized normal-sized individuals, shortening the duration of the meal did not reduce body weight.

In addition to body size, most of the participants originally ate for a long time and were not controlling their dietary energy.So if you’re in the normal range for your body type, don’t eat for a long time each day in the first place, or are already on a controlled diet, a time-restricted diet may not be effective for weight loss either.

2 Reasons for difficulties in adherence

Although the adverse effects of time-restricted diets are relatively few and mild, there have been cases of people experiencing dizziness, headache, nausea, vomiting, diarrhea and constipation, and not being able to continue to adhere to them as a result.Moreover, due to the long duration of fasting, if you have endocrine system abnormalities (abnormal blood sugar levels, etc.), you should consult your doctor in advance to see if it is feasible.

Finally, most of the enjoyable get-togethers related to eating and drinking are scheduled in the evenings, and as soon as the first meal is a little earlier, you can’t attend.This makes it difficult for party-lovers to stick to a time-restricted diet for long periods of time.

Restricted diets don’t necessarily make you thinner, and weight loss can start with cutting down on what you eat at night.This reduces the total amount of energy eaten throughout the day on the one hand, and results in fewer unhealthy snacks.On the other hand, it is more in line with the body’s biological clock, resulting in better weight loss and better health.