*For medical professionals only for reference
For a long time, people around you have always talked about losing weight and losing fat. When you mention fat, it feels like you are facing a great enemy. In fact, the "undercover" in fat - brown fat rich in mitochondrial can help us burn calories!
In addition to accelerating metabolism, brown fat seems to be closely related to reducing the risk of chronic diseases such as diabetes and cardiovascular disease . Since brown fat is so powerful, how can we activate it? It is said that exercise is effective, so can it be activated by exercise? I'm afraid the latest research findings will disappoint us a little.
22 scholars from five countries including Spain, Netherlands , the United States, Finland , and Chile published important research results on Nature Communications. They found that high-intensity supervision exercise failed to activate brown fat in adults with sedentary populations during the 24 weeks [1].
Although exercise activates brown fat from the perspective of mechanism and animal experiments, there seems to be no doubt that exercise can be activated. But this randomized controlled study broke our fantasy to a certain extent.
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fat, probably a nightmare like Singularity cake, which is always lingering for every weight loss (unsuccessful) person. But in fact, fat is also divided into several types: white fat (WAT) located under the skin, around the internal organs, and is responsible for energy storage, which is the culprit of gaining weight; and brown fat (BAT) rich in mitochondria and highly express uncoupled protein 1 (UCP1) is a "anti-freeze artifact" for maintaining body temperature [2].
study found that under cold stimulation, brown adipocytes can uncouple the electron transfer process in the oxidative transmission respiratory chain through UCP1 with the generation of ATP, thereby converting the mitochondria transmembrane proton gradient into thermal energy release. This process is called "non-trembling heat generation" (NST) [3].
This is also the reason why the most brown fat is in neonatal time. After all, newborn babies are not very likely to resist the cold outside by "shivering", skeletal muscle trembling.
In addition, the "hidden version" in fat - beige fat browned from white fat, has also attracted more and more attention. Beige fat is hidden in white fat and also expresses UCP1. When it encounters stimulation such as cold, it also has the "non-trembling heat generation" ability of brown fat [4].
In recent years, white fat browning and brown fat activation have become a new target for fighting obesity and its comorbidities [5]. So, as an important part of the "control your mouth and move your legs" weight loss method, can it also activate brown fat?
On the one hand, Mechanistically speaking, exercise can stimulate the production of many endocrine factors, thereby promoting brown fat metabolism and white fat browning [6]; and mouse experiments have shown that exercise can induce white fat browning [7-8], which may also be applicable to humans who are both mammals.
But on the other hand, exercise can also increase heat production, which may reduce the heat production activity of brown fat. In short, the academic community still knows little and is quite controversial in the issue of "what does exercise affect human brown fat" [9-10].
Therefore, Jonatan R. Ruiz et al. decided to conduct an randomized controlled trial (ACTIBATE trial [11]) to study the effects of 24 weeks of moderate or high-intensity supervised exercise on the volume of brown fat, 18F-FDG uptake, and average radiation density in sedentary adults.
is included in the group of young people aged 18-25, who do not smoke or take medication (including drugs that affect metabolism), have stable weight in the past 3 months, and people such as diabetes, hypertension and , or individuals who are often exposed to low temperatures (after all, low temperature can activate brown fat~).
145 subjects were randomly assigned to the control group (CON, N=54), the medium-intensity exercise group (MOD-EX, N=48) and the high-intensity exercise group (VIG-EX, N=43). 24 weeks later, a total of 107 people completed exercise training, excluding 10 subjects whose training course proportion did not meet the standards or had problems with experimental data collection, and 97 people were finally included in the subsequent statistical analysis.
In 24 weeks, subjects trained 3-4 times a week, completing 80 minutes of resistance exercise and 150 minutes of endurance exercise .Resistance training: 50% of the maximum number of repetitions (RM) were completed in the MOD-EX group, while 70% of the RM was completed in the VIG-EX. Endurance training: The MOD-EX group had 60% heart rate reserves (HRres), while the VIG-EX group had 75 minutes of exercise each week with 60% heart rate reserves and 80% heart rate reserves respectively.
Research flow chart
The key point is here! Will exercise activate brown fat? Regrettably, neither MOD-EX nor VIG-EX exercise regimens significantly changed the brown fat volume (Δ [after intervention-baseline]: ΔCON = −22.2±52.6 mL (mean±SD); ΔMOD-EX = −15.5±62.1 mL; ΔVIG-EX = −6.8±66.4 mL; p=0.771).
At the same time, exercise training also failed to change the 18F-FDG uptake of brown fat (standard intake value [SUV] mean: ΔCON=−0.4±0.7; ΔMOD-EX=−0.4±1.0; ΔVIG-EX=−0.5±1.1; P=1.000; SUV peak: ΔCON=−2.6±3.1; ΔMOD-EX=−1.2±4.8; ΔVIG-EX=−2.2±5.1; P=0.476).
SUV: standardized uptake value, standard intake value
average radiation density (representative of fat content) of brown fat also remained unchanged (ΔCON=−0.04±6.91 Horsfield unit [HU]; ΔMOD-EX=2.2±3.5 HU; ΔVIG-EX=−2.7±10.7 HU; P=0.441).
In addition, there was no significant difference in brown fat volume and 18F-FDG uptake in different body locations (i.e., posterior cervical area, supraclavicular area, mediastinum or paravertebral area).
In fact, a previous Finnish study in which 11 male subjects were included also showed that 6 weeks of moderate resistance training did not change 18F-FDG uptake of brown fat, but unfortunately, the control group was not included in the study, so it was difficult to rule out the effect of low temperature on the results [8].
So what are the findings of ACTIBATE included in the control group? , both in the control group and the medium/high-intensity exercise group, the outdoor temperature changes were significantly negatively correlated with the volume changes of brown fat, the 18F-FDG uptake changes and the average radiation density changes.
Although failed to successfully activate brown fat, , 24 weeks of supervised exercise training can lose weight and improve muscle and cardiorespiratory health. For example, compared with the control group, high-intensity exercise training reduced whole body fat and visceral fat , improved lower body muscle strength and peak oxygen intake, and extended exhaustion time.
However, blood pressure, fasting blood sugar , insulin , liver enzyme , blood lipid , etc. did not improve after exercise. Of course, this may be related to the fact that the subjects in this study were younger and relatively healthy.
VAT: visceral adipose tissue, visceral adipose tissue; RM: repetition maximum, maximum number of repetitions; VO2peak: oxygen consumption, peak oxygen uptake. * and † represent significant differences
So are the above improvements brought by exercise related to brown fat? (I want to try to get some facial features for brown fat~)
It’s a pity that there is no significant correlation between changes in brown fat-related results and changes in body composition, muscle strength or cardiopulmonary function caused by any exercise. In other words, the benefits of exercise training in this study were not mediated by brown fat activation.
In short, according to this study, 6 months of endurance + resistance exercise seems to be missing the chance to activate brown fat. But Singularity Cake firmly believes that the academic community will continue to study this "weight loss plug-in" and will bring us more scientific solutions to activate brown fat in the future.
References:
[1] Martinez-Tellez B, Sanchez-Delgado G, Acosta FM, et al. No evidence of brown adipose tissue activation after 24 weeks of supervised exercise training in young sedentary adults in the ACTIBATE randomized controlled trial. Nat Commun. 2022;13(1):5259. Published 2022 Sep 12. doi:10.1038/s41467-022-32502-x.
[2] Giralt M, Villarroya F. White, brown, beige/brite: different adipose cells for different functions?. Endocrinology. 2013;154(9):2992-3000. doi:10.1210/en.2013-1403.
[3] Li H, Qi J, Li L. Phytochemicals as potential candidates to combat obasity via adipose non-shivering thermogenesis. Pharmacol Res. 2019;147:104393. doi:10.1016/j.phrs.2019.104393.
[4] Castro É, Silva TEO, Festival WT. Critical review of beige adipocyte thermogenic activation and contribution to whole-body energy expenditure. Horm Mol Biol Clin Investig. 2017;31(2):/j/hmbci.2017.31.issue-2/hmbci-2017-0042/hmbci-2017-0042.xml. Published 2017 Sep 1. doi:10.1515/hmbci-2017-0042.
[5] Ruiz JR, Martinez-Tellez B, Sanchez-Delgado G, Osuna-Prieto FJ, Rensen PCN, Boon MR. Role of Human Brown Fat in Obesity, Metabolism and Cardiovascular Disease: Strategies to Turn Up the Heat. Prog Cardiovasc Dis. 2018;61(2):232-245. doi:10.1016/j.pcad.2018.07.002.
[6] Sanford JA, Nogiec CD, Lindholm ME, et al. Molecular Transducers of Physical Activity Consortium (MoTrPAC): Mapping the Dynamic Responses to Exercise. Cell. 2020;181(7):1464-1474. doi:10.1016/j.cell.2020.06.004.
[7] Lehnig AC, Dewal RS, Baer LA, et al. Exercise Training Induces Depot-Specific Adaptations to White and Brown Adipose Tissue. iScience. 2019;11:425-439. doi:10.1016/j.isci.2018.12.033.
[8] De Matteis R, Lucertini F, Guescini M, et al. Exercise as a new physical stimulus for brown adipose tissue activity. Nutr Metab Cardiovasc Dis. 2013;23(6):582-590. doi:10.1016/j.numecd.2012.01.013.
[9] Motiani P, Virtanen KA, Motiani KK, et al. Decreased insulin-stimulated brown adipose tissue glucose uptake after short-term exercise training in healthy middle-aged men. Diabetes Obes Metab. 2017;19(10):1379-1388. doi:10.1111/dom.12947.
[10] Motiani P, Teuho J, Saari T, et al. Exercise training alters lipoprotein particles independent of brown adipose tissue metabolic activity. Obes Sci Pract. 2019;5(3):258-272. Published 2019 Apr 24. doi:10.1002/osp4.330.
[11]https://clinicaltrials.gov/ct2/show/NCT02365129?term=NCT02365129draw=2rank=1.
Author of this article丨davina
Editor丨Daisiyu
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