The mice had to climb a 70-centimeter staircase while
carrying a weight attached to their tails to simulate strength training.
Credit: Leandro Moura
Just seven days of strength training increased visceral fat burning in
obese mice, even before any weight loss could be seen on a scale. In an
experiment conducted at the State University of Campinas (UNICAMP), researchers
observed that a short period of strength training activated mechanisms involved
in fat breakdown, reduced fat cell size and decreased fat around the animals'
intestines.
The study, published in the
journal Life Sciences, aimed to understand how adipose tissue responds
at the beginning of strength training, before weight loss could affect the
results.
The study is part of a research line that has investigated how physical
exercise affects metabolic health for nearly 20 years. Since 2007, the group
has studied the mechanisms involved in the effects of physical activity on
conditions such as obesity and diabetes. With advances in molecular analysis
techniques, the researchers began investigating not only the visible effects of
exercise, such as weight loss or muscle mass gain, but also the changes that
begin to occur within cells.
"We've always heard that physical exercise burns fat and helps you
lose weight. But we rarely stop to think about how that happens,
how much exercise is needed, and what that fat burning actually means,"
says Leandro Moura, a physician, physical education professional, professor at
UNICAMP, author of the study and coordinator of the Exercise Cell Biology Lab
(ECeBiL). This group is dedicated to studying the physiological, metabolic and
biomolecular adaptations induced by physical exercise and sports.
The training
The tests were conducted on male mice. One group was fed a standard diet,
while another was fed a high-fat diet to induce obesity. The obese animals were
then divided into two groups. One group remained sedentary, while the other
began strength training. The high-fat diet continued throughout the exercise
period so that the only difference between the groups would be physical
activity. This allowed the effects of strength training to be isolated.
The mice had to climb a 70-centimeter (28-inch) staircase while carrying a
weight attached to their tails to simulate strength training. Each session was
conducted at 70% of maximum capacity and included 20 climbs with rest intervals
of 60 to 90 seconds. In total, there were seven sessions.
"We calculated how much weight each mouse could carry while climbing a
staircase. Obviously, it isn't possible to replicate the exact strength
training exercises performed by a person, but we were able to induce a similar
effort in the body, with more intense contractions, effectively mimicking a
strength training session for humans," Moura explains.
The analyses focused on mesenteric adipose tissue, the layer of fat
surrounding the intestines. According to Moura, this tissue is the primary
representative of "visceral fat" in humans—the fat that accumulates
deep within the abdomen, among the vital organs. This fatty tissue is far more
harmful to health than subcutaneous fat, which is located just beneath the
skin. When present in excess, visceral fat releases inflammatory substances
directly into the bloodstream, altering the metabolism of the entire body.
The researcher explained that the decision to monitor the impact of
strength training on the animals for only seven days was intentional. They
wanted to observe the effects of strength training on adipose tissue before any
weight loss occurred because weight loss itself triggers various bodily changes
that could mask the direct effects of exercise.
"When we're able to maintain the same body weight and observe what
happened in the body, we can directly isolate what physical exercise
contributed to before weight loss," Moura explains. The two groups of
obese animals were fed the same diet throughout the experiment to avoid
introducing another variable.
Although their total body weight did not decrease during this time, the
mice that did strength training had less mesenteric adipose tissue mass than
the sedentary obese animals. Additionally, their adipocytes (cells responsible
for storing fat) were smaller.
The size of these cells is important for metabolic health. In obese
individuals, adipocytes swell so much that they undergo chronic stress and
begin secreting inflammatory substances into the bloodstream. The fact that
exercise shrinks these cells proves that the tissue is no longer inflamed and
is becoming metabolically healthy, even before there is any change on the
scale.
The metabolic mechanism involved
When the researchers investigated what was happening inside these cells,
they discovered that obesity had impaired the action of proteins that are
important for lipolysis, or the process of breaking down stored fat so that it
can be used as an energy source. After seven strength training sessions, part
of this mechanism began functioning again.
The proteins analyzed included PLIN1 (perilipin-1), ABHD5 and ATGL. In
simple terms, PLIN1 helps regulate the fat stored within fat cells. When
stimulated by exercise, PLIN1 undergoes a change and releases ABHD5, which
activates the breakdown of fat. Once released, ABHD5 binds to ATGL, an enzyme
involved in the first step of breaking down triglycerides stored in the cell.
The study also found a reduction in the expression of the Scd1 gene, which is
involved in synthesizing fat molecules. This suggests that the body becomes
less prone to storing dietary calories in adipose tissue.
In sedentary, obese mice, however, ABHD5 levels were reduced, so the
fat-breaking mechanism was not significantly activated. Strength training
increased the interaction between ABHD5 and ATGL, activating other markers
involved in lipolysis.
"People tend to think that if they've been strength training for two
months and haven't lost weight, it hasn't done any good. But what we saw in
this study is that after just seven days of strength training—even when there
was still no weight loss—the molecular pathways that promote fat accumulation
were less active, while those that stimulate fat breakdown were more
active," Moura comments.
According to the researcher, the results help dispel the notion that only
aerobic exercise contributes to weight loss and that strength training only
increases muscle mass. "Both types of exercise activate similar
pathways—at different intensities—as well as different pathways. Therefore,
combining the two remains the best recommendation and the best strategy for
those who want to lose weight," says Moura.
Next steps
It is important to note that these findings are still experimental. In
other words, one should not assume that seven days of strength training will
produce the same effects in humans. This study was conducted on male mice only,
assessed a single fat deposit and analyzed only genes, proteins and molecular
signals related to fat breakdown.
The team plans to monitor longer training periods to understand how these
responses evolve as weight loss begins to occur. The researchers are also
investigating the effects of exercise on other fat deposits, including those
around the heart.
Moura says the study sends a message to those who are just starting to
exercise and expect immediate results on the scale. "Even if we aren't
seeing anything yet with the naked eye, metabolically, inside our bodies,
various signals that are beneficial to health—including weight loss—are taking
place. That's why we shouldn't get discouraged by the lack of visible results
after a short period of strength training," the researcher concludes.
Source: Strength training causes fat cells to shrink even before weight loss, study suggests
No comments:
Post a Comment