March, April and May do not lose weight, and June and July and August are sad. Summer is approaching, and there is a wave of "weight loss" - ketogenic diet, 16:8 light fasting, alternate-day fasting and other fat loss methods emerge one after another, who doesn't want to lose weight into lightning before summer comes?
Ketogenic weight loss seems to be a big rollover, so what to do? How about trying intermittent fasting? I feel that this diet diet seems to be quite reliable?!
Source: Photogram
Intermittent fasting (IF) is an alternating eating and fasting diet, that is, eating food normally for a certain period of time (usually 6-10 hours as the eating window) and hardly eating for the rest of the day. In life, the most adopted is the 16:8 light fasting method, alternate day fasting method, and 5+2 fasting method, but some people will adopt a more extreme 23:1 method.
Scientists have been exploring the benefits and harms of intermittent fasting, but controversy continues. Previous studies have shown that not only weight loss, intermittent fasting can effectively improve brain health and even extend life; However, there are also many scholars who hold the opposite opinion, believing that intermittent fasting has certain drawbacks and potential harms.
Recently, the study published in the Cell sub-journal Immunity gave a "warning" - intermittent fasting may cost health "costs"! Experiments have shown that prolonged fasting can cause a stress response in the brain and have a more negative impact on immune cells, which will be detrimental to fighting infections and increasing the risk of heart disease.
It seems that it is really "not fasting right, immune collapse"!
https://doi.org/10.1016/j.immuni.2023.01.024
To assess the effects of fasting (from a few hours for a shorter period of about a few hours to a longer 24-hour period) on the immune system, the researchers divided the mice into two groups - the fasting group did not consume any food in the 24-hour period of the experiment, but did not limit the number of times they drank, and could eat freely after 24 hours of fasting; The control group had free access to food. Changes in major white blood cells in 16 organs and tissues, including B lymphocytes, T lymphocytes, monocytes, and neutrophils, were recorded during the 24-hour fasting period.
The results showed significant differences between the fasting and control groups. The number of Ly-6Chi monocytes in each tissue was reduced except for the bone marrow compared to the control group.
The specific change was that the number of monocytes in all mice remained at the same level at baseline. But what is very exaggerated is that after only 4 hours of fasting, the number of monocytes in the blood of the mice in the test group was reduced by 90%! After 8 hours, this value decreased further. In contrast, the monocytes in the fasting group showed no changes.
So, what kind of problems does monocytopenia bring?
Monocytes are white blood cells made in the bone marrow that travel through the body and play important immune roles, including fighting infections, heart disease, and cancer. In other words, a decline in the number of monocytes naturally means that immune function has been damaged to some extent.
Fasting changed the distribution of white blood cells in mice
In addition, the researchers also found that fasting caused Ly-6Chi monocytes in the blood to rush back to the bone marrow and "hibernate" there. At the same time, the number of new cells produced in the bone marrow decreased.
But when it comes back to the bone marrow, the life cycle of monocytes is affected – unlike monocytes in the blood, monocytes in the bone marrow survive longer and the aging process changes.
So, what is driving this phenomenon?
In further genetic analysis, Cxcr4 caught the researchers' attention – they found that Cxcr4 expression was nearly 4 times higher than in the control group under fasting; The role of the Cxcr4 gene is to promote the retention of cells in the bone marrow.
In fact, previous studies have suggested that cortisol (CORT) enhances Cxcr4 expression. In this study, the researchers observed that fasting rapidly and consistently increases CORT in the blood, which in turn leads to an increase in Cxcr4 expression. Cxcr4 expression is increased, and Ly-6Chi monocytes naturally migrate from the blood to the bone marrow, where they aggregate.
Fasting causes monocytes to return from the blood to the bone marrow
So since fasting is not good, re-eating can always be restored, right?
Not really! One prohibition and one entry exacerbates the inflammatory response. After feeding mice fasted for 24 hours, the researchers showed "unexpected" results:
Monocytes hidden in the bone marrow return to the bloodstream within 4 hours of eating. The proliferation of circulating monocytes exacerbates the inflammatory response; These monocytes after "bone marrow reconstruction" not only cannot fight infection, but are more inflammatory, making the body's ability to resist infection decrease.
In fact, this fasting + eating pattern not only has an impact on the immune system in the short term, but lasts for a long time - in the short term, the activity of class II antigen presentation, interferon β (IFNb) recombinant protein in monocytes decreases, and innate immune characteristics are reduced; In the long term, the fasting group was more likely to die than the control group, and the time of death was earlier.
In summary, compared with the control group, the pattern of long-term fasting + eating can lead to an imbalance of monocytes in the blood and bone marrow in a short period of time, thereby increasing the inflammatory response in the body, changing the host's immunity to infection, and leading to higher mortality.
Refeeding causes monocytes to rush into the bloodstream
The "cow" of this study is that this is the first study to link the brain and its neurons during fasting to immune cells - fasting causes a stress response in the brain (which is why "hunger" makes people angry), which then triggers a large number of white blood cells to migrate from the blood to the bone marrow, and after eating, the migration "turns", and a large number of monocytes return to the bloodstream, inducing an inflammatory response.
"Therefore, the pattern of fasting to lose weight does not work for everyone, and this approach is not conducive to the body's coping with the challenges of infection." Dr. Swirski, one of the leaders of the study, said,
There is no end to the law! Intermittent fasting is not "perfect", how to choose the right weight loss method for yourself to avoid harm, but also "according to people's conditions". Don't sacrifice your health in order to blindly pursue "thinness", some gains are not worth the loss!
Resources:
https://doi.org/10.1016/j.immuni.2023.01.024
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