Just 7 days of strength training started shrinking fat cells in mice
Just seven strength-training sessions helped obese mice shrink visceral fat cells and reactivate molecular pathways involved in burning stored fat, despite no change in overall body weight. The findings suggest some benefits of resistance exercise may begin long before weight loss becomes visible, though the results still need to be confirmed in humans.
Key points
- Seven days of strength training reduced visceral fat and shrank fat cells in obese mice without any change in body weight.
- The exercise reactivated part of the molecular fat-breakdown system that obesity had disrupted.
- Researchers caution the results are experimental and may not apply to people.
A study from the State University of Campinas (UNICAMP) found that just seven days of strength training increased visceral fat breakdown in obese mice, even though their body weight had not yet changed. The research, published in Life Sciences and supported by FAPESP, showed that the exercise activated biological processes that break down stored fat, reduced the size of fat cells, and lowered the amount of fat surrounding the animals' intestines.
The experiments used male mice. One group ate a standard diet, while another received a high-fat diet to induce obesity. The obese mice were split into a sedentary group and a group that completed a strength training program. Both obese groups continued eating the same high-fat diet during the experiment.
How the training was done
To mimic strength training, the mice climbed a 70-centimeter staircase while carrying weights attached to their tails. Each workout was performed at 70% maximum capacity and consisted of 20 climbs, with 60 to 90 seconds of rest between climbs. The animals completed seven training sessions in total.
The researchers focused on mesenteric adipose tissue, which surrounds the intestines and is the primary representative of visceral fat in humans. Visceral fat is considered more harmful than subcutaneous fat because when it becomes excessive, it can release inflammatory substances into the bloodstream.
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.
— Leandro Moura
What the analysis showed
Despite no reduction in total body weight, the trained mice had less mesenteric adipose tissue than the sedentary obese mice, and their adipocytes were smaller. The researchers also found that obesity had disrupted proteins involved in lipolysis, the process through which stored fat is broken down. After seven strength training sessions, part of this fat breakdown system had begun functioning again.
The study detected lower expression of the Scd1 gene, suggesting the body may become less inclined to store calories from food as fat. The researchers caution that the results remain experimental and do not mean seven days of strength training will necessarily produce the same effects in people. The study included only male mice and examined a single type of fat deposit.
