Strength Training Breaks Down Fat Cells in Obese Mice After One Week

A groundbreaking study has revealed that just one week of strength training can significantly impact fat cell breakdown in obese mice, even when their body weight remains unchanged. Researchers at the State University of Campinas have discovered a rapid activation of biological processes that break down stored fat after only seven days of exercise.

The study aimed to explore what happens to adipose tissue during the early stages of strength training, before any noticeable weight loss could influence the results. This research is part of a larger body of work on how physical activity affects metabolic health, supported by FAPESP and dating back nearly two decades.

Since 2007, the research group has been investigating the biological mechanisms behind exercise's effects on conditions such as obesity and diabetes. Advances in molecular analysis techniques have allowed them to delve deeper into cellular changes, moving beyond visible outcomes like weight loss and muscle gain.

The study's findings suggest that physical exercise can have an immediate impact on fat cell breakdown, even if it hasn't yet led to significant weight loss. This raises questions about the optimal duration and intensity of exercise for weight management.

As part of this research, scientists at the Exercise Cell Biology Lab (ECeBiL) are dedicated to understanding how physical activity affects physiological, metabolic, and biomolecular processes in the body.

The experiments involved male mice, with one group receiving a standard diet and another being fed a high-fat diet to induce obesity.

These obese mice were then divided into two groups, with one remaining sedentary while the other underwent a strength training program despite consuming the same high-fat diet as their counterparts.

To replicate strength training in the lab, researchers had the mice climb a 70-centimeter staircase attached to weights on their tails. Each workout consisted of 20 climbs at 70% maximum capacity, with rest periods between climbs.

The animals completed seven training sessions, and the effort required from them was calculated based on how much weight each mouse could carry while climbing the stairs.

This approach allowed researchers to focus specifically on mesenteric adipose tissue, which surrounds the intestines in mice. This type of fat is similar to visceral fat found deep within the abdomen in humans.

The distinction between visceral fat and subcutaneous fat is significant when it comes to their impact on health. Visceral fat, which accumulates deep within the abdomen, poses a greater threat to metabolic well-being than its subcutaneous counterpart.

Researchers designed their experiment with a deliberate seven-day training period in mind. By doing so, they aimed to isolate the effects of exercise on fat tissue before weight loss set in, as shedding pounds can trigger additional physiological changes that complicate the analysis.

When we maintain the same body weight and observe what happens within the body, Moura notes, we can pinpoint the direct contribution of physical exercise. To rule out any variables related to diet, both groups of obese mice were fed identical meals throughout the experiment.

Despite not showing a decrease in overall body weight, the mice that engaged in strength training had less mesenteric adipose tissue than their sedentary counterparts. Moreover, their adipocytes, cells responsible for storing fat, were noticeably smaller.

The reduction in fat cell size is a crucial indicator of improved metabolic health. In obese individuals, chronically stressed adipocytes can release inflammatory substances into the bloodstream. The shrinking of these cells following exercise suggests that the tissue is transitioning toward a healthier state even before visible weight changes occur.

The researchers took a closer look at what's happening inside the fat cells of these mice to understand how exercise is impacting their biology.

They found that obesity has disrupted certain proteins involved in breaking down stored fat and making it available for energy. This process is known as lipolysis, and when it's working properly, the body can efficiently use stored fat as fuel.

After just seven strength training sessions, some of this fat breakdown system began to function again. The scientists examined three key proteins: PLIN1, ABHD5, and ATGL, which play crucial roles in regulating how fat is stored and broken down inside fat cells.

PLIN1 helps control the storage of fat within these cells, while ABHD5 and ATGL work together to initiate the breakdown of triglycerides. When exercise stimulates PLIN1, it triggers a chain reaction that releases ABHD5, which then binds to ATGL to start the process of breaking down stored fat.

The team also discovered lower expression of the Scd1 gene in these mice, suggesting that their bodies may be less inclined to store calories from food as fat. This finding implies that even before noticeable weight changes occur, exercise can have a profound impact on how the body processes and stores energy-rich molecules.

The findings of this study suggest that strength training can have a significant impact on fat cells, even before noticeable weight changes occur.

While it's commonly believed that aerobic exercise is mainly responsible for weight loss, the researchers argue that both types of exercise activate similar pathways and different pathways at varying intensities.

This means that combining strength training with aerobic exercise could be an effective strategy for those looking to lose weight. However, it's essential to note that these results are still experimental and may not translate directly to humans.

The study focused on male mice and a specific type of fat deposit, examining genes, proteins, and molecular signals associated with fat breakdown. Future research will investigate how exercise affects other types of fat deposits in the body.

The team is also planning to follow animals through longer training periods to see how these early changes develop once weight loss begins.

Research has shown that just seven days of strength training can have a significant impact on fat cells in mice, leading to a reduction in their size.

This finding builds upon previous studies examining the effects of exercise on fat loss and may have implications for human health as well, particularly with regards to visceral fat.