Geschatte leestijd: 4 minuten
With training, you not only reduce fat mass or increase muscle mass. Training also changes the fat itself, which can improve metabolism.
Training and fat mass
When we think about training and fat mass, we often focus on a few positive effects.
For example, we can try to improve the energy balance. By moving more and thereby consuming more energy, you can try to lose weight, for example. Making sure you consume less energy can be achieved through adjustments to your diet, of course, is the other option.
Training also leads to more muscle mass. Many studies focus on the positive effects of increased muscle mass. Think of a higher resting energy expenditure, but also increased sensitivity to glucose. Muscles are major users of glucose. A higher capacity to uptake glucose in muscle mass reduces the risk of diabetes and also reduces the amount of glucose stored in fat cells.
We have probably already written dozens of articles on this blog about these studies, but also about studies on the effects of fat burning through training. This is indeed what science mainly focuses on when looking at the effects of training. After all, higher fat mass is associated with several health disadvantages.
However, new research shows that training also has a positive effect on characteristics of the fat cell itself. So, you are not only training for less fat mass and/or more muscle mass, you are also training to make the fat mass itself less unhealthy.
Harmful and Positive Proteins Released by Fat Cells
Some of the unhealthy effects of high fat mass can be attributed to
adipokines. Fat cells are not just a fuel reserve. Fat is an organ that communicates with the brain and surrounding organs. This communication occurs through proteins that can be released by fat cells, called adipokines. With an increase in fat mass, we also see an increase in the amount of adipokines and unfortunately, many adverse effects are attributed to those proteins. One of the major problems with obesity is that it puts the body in a constant state of inflammation. The majority of adipokines promote inflammation [1]. However, a few adipokines have been found to have anti-inflammatory effects.
Researchers are identifying more and more different types of adipokines. One of these proteins that is receiving a lot of attention is adiponectin. This protein has been identified as a key player in obesity, insulin resistance, diabetes, and cardiovascular diseases [2,3]. Adiponectin increases insulin sensitivity and therefore reduces the risk of diabetes. Unfortunately, adiponectin levels are decreased in overweight individuals.
A more familiar example of such a protein released by fat cells is leptin, also known as a ‘hunger hormone.’ Leptin can be seen as the gauge that indicates how much fuel is left in your car. Lower levels indicate an empty tank, higher levels a full tank. This protein provides information to the brain and thus influences appetite. Administration of leptin in mice results in significantly reduced food intake. However, this is less effective in humans.
Training and Adipokines
Researchers at the Joslin Diabetes Center have recently discovered another adipokine that, like leptin, has positive properties [4]. Two years ago, the researchers were the first to demonstrate that fat mass can have beneficial effects on metabolism in response to exercise.
The researchers conducted experiments with both humans and mice. They found that training caused significant changes in the fat cells. This “trained” fat resulted in the release of the adipokine
growth factor beta 2 (TGF-beta 2) into the bloodstream.
In contrast to the negative effects of many adipokines, our study identified transforming growth factor beta 2 (TGF-beta 2) as an adipokine released from adipose tissue (fat) in response to exercise that actually improves glucose tolerance.
Laurie J. Goodyear, Joslin Diabetes Center
This release of TGF-beta 2 through training not only improved glucose tolerance but also reduced the amount of fatty acids in the bloodstream. The fact that a single protein had these and other positive effects on metabolism is seen as very promising by the researchers.
Our hypothesis was that exercise is changing the fat, and as a result of that change, the fat releases these beneficial proteins into the bloodstream. Before this discovery, we always just focused on the positive effects of muscle.
“Good Fat”
While many scientists are studying brown and beige fat, the researchers at Joslin were looking for good properties of ‘the bad’ white fat under the influence of training. They looked at the levels of adipokines in humans and mice before and after a training cycle.
From their analysis, they identified TGF-beta 2 as one of the proteins that was released to a greater extent by fat cells in response to training. Follow-up research confirmed that this adipokine increased after training, both in the fat tissue itself
and in the bloodstream.
The next step was to look at the effects of TGF-beta 2. For this, they treated mice with this protein. Instead of letting them exercise, they increased the levels of this protein by administering it themselves. The experiment showed multiple positive effects including improved glucose tolerance and increased uptake of fatty acids.
They then put mice on a high-fat diet resulting in the development of diabetes. These diabetic mice were treated with TGF-beta 2. This reversed the negative effects of the fatty diet, similar to the effect of training.
This is the first study to show that through training, adipokines can be released with positive effects on metabolism.
Lactate, incidentally, was found to play an important role. Released by muscles during training, it travels through the bloodstream to fat cells where it stimulates the release of TGF-beta 2.
Why is this important?
Further studies on the safety of (administration of) TGF-beta 2 will determine to what extent this protein can help in the future as medication in the fight against diabetes and other diseases caused by metabolism. But even if you want to work on your health ‘on your own,’ this knowledge can be motivating.
If you only see fat burning or extra muscle mass as your goal, it may seem unjustified if you don’t see a difference in this yet. Knowing that you may not have reduced your fat mass, but have made it less unhealthy, can prevent you from giving up.
References
- Ouchi N, Parker JL, Lugus JJ, Walsh K. Adipokines in inflammation and metabolic disease. Nat Rev Immunol. 2011;11(2):85-97.
- huderf.be/nl/edu/diabeto/pdf/perc-vetweefsel.pdf
- Rabe K, Lehrke M, Parhofer KG, Broedl UC. Adipokines and insulin resistance. Mol Med. 2008;14(11-12):741-51.
- Takahashi et al. TGF-B2 is an Exercise-Induced Adipokine that Regulates Glucose and Fatty Acid Metabolism. Nature Metabolism, 2019 DOI: 10.1038/s42255-018-0030-7
