In recent years, there has been a lot of scientific news about the benefits of the light fasting method, which has aroused a lot of interest. Compared with the traditional weight loss method of "controlling your mouth and opening your legs", does it really have an advantage? What about the long-term results?
Recently, a study on light fasting published in Nature Medicine has attracted a lot of attention. I would like to take this opportunity to give you a detailed talk about the results of the research.
Maybe you've seen other related science news, but I might interpret it differently. If you don't want to see the detailed research process, please browse the key content, and then scroll to the back to see the summary.
In fact, there have been many studies on light fasting in recent years. What is new about this study is that it combines two light fasting methods, "interval fasting" and "time-restricted eating", with trials lasting up to 6 months and tracking for up to 18 months.
Many nutrition experiments are controlled feeding experiments, that is, all foods are provided by researchers, raw materials and cooking methods are precisely managed, and subjects are not allowed to eat casually. Doing so, while scientifically accurate, is too costly and difficult to sustain in the long term. In this study, the subjects ate at home and lived a normal life.
1 Participants and study groups
After screening, the researchers recruited an obese population with an average mass index (BMI) of about 35, an average weight of about 100 kg, and an average waist circumference of about 110 cm. Moreover, their blood sugar, blood pressure, and blood lipids must be normal, and they cannot have liver and kidney diseases, in short, they are healthy fat people.
Highly obese and normal physical examination indicators - these are healthy and excellent individuals among fat people, containing more than 50 kilograms of muscle in the body. Therefore, the methods and results of this study are not necessarily applicable to those who are not severely obese, nor are they necessarily applicable to those who are obese and sick.
The 209 subjects were randomly divided into 3 groups in a 2:2:1 ratio, the first group was time-restricted light fasting (iTRE), the second group was the traditional calorie restriction (CR), and the third group was standard care (SC), that is, the control group.
Time-restricted light fasting group: Light fasting 3 days a week and eating only 30% of normal calories in a day. These three days are not consecutive. That is, it can be Monday, Wednesday, Friday, or Tuesday, Thursday, Saturday. Moreover, on days of light fasting, you can only eat at 8~12 a.m., and fast for 20 hours after that. On other days, you can eat normally, regardless of the variety or quantity. Send two bags of meal replacement powder for fasting days, one bag to eat at 8 o'clock and one bag to eat at 12 o'clock. There is one-on-one counseling from a dietitian.
(Researchers may be concerned that eating so little in a row will affect health.) Fat people can't bear continuous hunger. ）
Traditional calorie reduction group: On the basis of maintaining a basic balance of nutrition, eat 30% less calories every day. There are recipes that rotate weekly, including meals and snacks. Have meal replacement powder with meals to help control calories and replenish nutrients. However, there is no restriction on the time to eat at all. There is one-on-one counseling from a dietitian.
Control group: Give subjects a booklet of standard weight loss instructions and read it for themselves. There is no professional consultation and no meal replacement products.
2 Research results
By 6 months, the weight loss effect of the time-restricted light fasting group compared with the traditional calorie reduction group was as follows:
Time-limited light fasting group: weight lost 7.38 kg, waist circumference lost 6.80 cm, hip circumference lost 5.52 cm, fat lost 6.19 kg, non-fat weight (mainly muscle) lost 1.86 kg, visceral fat lost 0.51 kg.
Traditional calorie group: 6.98 kg of body weight, 6.44 cm of waist circumference, 4.68 cm of hip circumference, 5.76 kg of fat, 1.34 kg of non-fat weight (mainly muscle), and 0.48 kg of visceral fat.
The traditional calorie reduction group seemed to lose a few tenths of a kilogram of fat, but it also lost a few tenths of a kilogram of muscle. Small differences, all within the margin of error. Scientifically speaking, there were no significant differences. The effect of both is good, much better than the control group.
However, for a person weighing 100 kilograms, losing less than 5% of his weight in 6 months is really not a magic method. The seemingly new concept of time-limited light fasting methods also does not show advantages over traditional weight loss methods.
Then, various biochemical indicators were compared. Both weight loss methods performed better than the control group on fasting blood glucose, glycosylated hemoglobin, blood pressure and cholesterol indicators, but there was no significant difference between the two.
So, what are the advantages of the time-limited light fasting method?
The results showed that after eating a standard liquid test meal, the time-restricted light fasting group had a lower postprandial blood glucose response, better improved insulin sensitivity, and reduced triglyceride levels compared with the traditional calorie-reducing group.
In addition, β-hexosaminidase β activity was lowest in the time-restricted light fasting group. This is an indicator related to aging. This indicator rises in people with diabetes, Alzheimer's and liver disease.
All in all, compared with ordinary weight loss methods, the effect of time-limited light fasting is not as miraculous as expected, mainly because it performs better in insulin sensitivity indicators.
3 Follow-up tracking
It is possible that most of the relevant reports only pay attention to the results of the first 6 months, but do not talk about the subsequent impact.
First, are subjects willing to continue to adhere to these weight loss methods?
By the end of 6 months, more than half of participants in the time-restricted fasting group indicated that they wanted to adjust their approach. A whopping 97% of people in the traditional weight loss method group said they would like to continue this weight loss method.
Secondly, by the 18th month, what is the difference in the effect of each weight loss method?
By the 18th month, although 42% of the time-restricted light fasting group said they were still sticking to it, and 78% of the traditional weight loss group said they continued to control their diet, the effect had rebounded.
The light fasting group lost 7.59 kg of body weight, rebounded back with an average of 3.34 kg, and the reduction in triglycerides rebounded almost completely. The advantages of insulin sensitivity are also less pronounced than before.
The traditional weight loss method reduced 6.99 kg, the average rebounded back to 1.76 kg, triglyceride levels not only did not rebound, but also continued to decline.
The difference in the effect of the two weight loss methods and the control group has also been greatly reduced, and the effect of weight loss is only 2 kg, and many health indicators have no significant difference.
Third, what are the subsequent effects of weight loss measures on subjects' physical sensations?
During the 6~18 months return visit period, many subjects reported their health problems, the most common of which was flu-like symptoms. Moreover, both the time-restricted and traditional calorie reduction groups reported 45%, significantly higher than the 19% in the control group.
The virus is never far away! It's up to our immune system to resist day and night! As long as the nutrient supply is a little bit, the body is slightly weak, and it can be knocked down.
Among respondents in the time-restricted fasting group, 56% reported frequent fatigue, 33% reported constipation, and 26% reported headaches; The proportion of fatigue, constipation, and headache in the traditional caloric reduction group was 37%, 27%, and 26%, compared with 35%, 5%, and 6% in the control group. There are also reports of dizziness.
Obviously, after 6 months of weight loss measures, the overall health level of the body has decreased, and the effect of time-restricted light fasting may be greater.
To summarize briefly:
1 This study mainly compares the effect of time-restricted light fasting (light fasting for 3 days a week, which can only eat 30% of the normal amount of food in these 3 days, and can only eat at 8~12 o'clock) and the traditional calorie reduction balanced diet. Both groups have professional supervision. There is also a control group, which has no professional guidance and follows the guidance of the health booklet to lose weight.
2 This study was conducted in severely obese people with an average weight of 100 kg. The methods and results may not be appropriate for people of normal weight, as well as people who are mildly fat.
Within 3 half a year, under the guidance and supervision of professionals, time-limited light fasting weight loss methods can improve insulin sensitivity and reduce triglyceride levels more effectively than traditional weight loss methods, which may be good for the prevention of diabetes.
4 In terms of weight loss efficiency and fat loss efficiency, there is no obvious difference between the time-limited light fasting method and the traditional calorie weight loss method. However, the two groups with professional guidance performed better than the group without professional guidance, losing an average of about 4.5 kilograms more in half a year.
5 In terms of blood pressure, fasting blood sugar, blood cholesterol indicators, etc., the time-limited light fasting method is not more advantageous than the traditional calorie reduction and weight loss method. But both groups with professional guidance worked better than those without professional guidance.
6 Time-limited light fasting method: half of the participants wanted to adjust the method after six months. More participants are willing to continue their efforts with traditional calorie reduction methods.
7 and a half years later, without professional guidance and supervision, both methods have a certain degree of weight rebound, and the gap between health indicators and control groups narrows, or even disappears,
8 Compared with the control group, whether it was a time-limited light fasting method or a traditional calorie reduction and weight loss method, after half a year, a larger proportion of people had flu-like symptoms (infection with respiratory viruses), and at the same time felt daily physical discomfort, such as fatigue, headache, dizziness, constipation, etc.
In short, the time-limited light fasting method, put in a time range of one and a half years, compared with traditional weight loss methods, has no advantage in health effects, and it is more difficult to adhere to it for a long time.
Especially when the epidemic is not over, reducing food intake and restricting eating times may lead to nutritional deficiencies and stress responses, thereby reducing resistance to the virus.
Do you still want to choose those "new" ways to lose weight?
Something:
Whether it's a very low-carbohydrate diet or a time-limited light fast, various fashionable weight loss methods can only show more prominent results in the time dimension of a few months. In studies lasting a year or more, none showed any advantage, and some even showed more rebound, more adverse health effects, and adverse psychological effects, such as making it harder to live peacefully with food.
But life isn't just a few months. Statistics show that the peak weight of men and women is around the age of 55 and around 65, respectively. That is to say, for young people, as they age, people will become more and more likely to gain weight. Weight control is a long-term task. Any approach that is not sustainable over the long term will not succeed.
So, as one of the advertising slogans says, "I'm still willing to go back to basics." Abandoning those dreams of taking shortcuts, paying attention to dietary nutrition steadily, changing bad habits, increasing physical activity, and exercising regularly is the long-term solution to maintaining a healthy body.
Related Literature:
Teong XT, Liu K, Vincent AD, et al. Intermittent fasting plus early timerestricted eating versus calorie restriction and standard care in adults at risk of type 2 diabetes: a randomized controlled trial. Nature Medicine, April 6, 2023