Strength Training Improves Fat Cells Before Weight Loss

A host of biological changes take place in the body when a person begins to lose weight.

For scientists examining the effects of diet, exercise or another influence, separating the consequences of weight loss from the factor under investigation can be challenging.

Strength training and fat cells before weight loss

To better understand how strength training affects fat cells before weight loss begins, researchers at the University of Campinas in Brazil conducted a week-long experiment involving obese mice.

They examined visceral fat, which surrounds the organs, before the animals had begun to lose weight.

Compared with obese sedentary mice, those following the strength-training programme had less fat around their intestines and smaller fat cells, a feature that generally points to healthier fat tissue.

The researchers also found indications of beneficial shifts in the signals involved in storing and breaking down fat.

Published in Life Sciences, the findings indicate that strength training may improve metabolic health before it leads to weight loss. However, the results must still be reproduced in trials involving people.

"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," says physician Leandro Moura.

"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."

How the mouse strength-training programme worked

To model the effects of weight training, the researchers had the obese mice climb a 70-centimetre staircase while weights were attached to their tails. Each session involved 20 climbs, separated by 60–90-second rest intervals, at 70 percent of the rodents' maximum capacity. The mice completed seven sessions in total.

"We calculated how much weight each mouse could carry while climbing a staircase," says Moura.

"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."

The fat-tissue samples from the strength-trained mice were subsequently compared with samples from obese mice that had not exercised.

Proteins linked to fat storage and breakdown

Alongside the effects already identified, the researchers assessed two proteins: ABHD5 and ATGL. ABHD5 helps drive the breakdown of fats. Its levels were lower in the obese sedentary mice, whereas levels were normal in the strength-training group. Interactions with ATGL, an enzyme that breaks down fat, also increased.

The exercised mice additionally showed reduced activity of the Scd1 gene, which is involved in fat production. Together, these findings suggest that strength training could complement aerobic exercise in efforts to reduce weight, the researchers say.

"Both types of exercise activate similar pathways – at different intensities – as well as different pathways," says Moura.

"Therefore, combining the two remains the best recommendation and the best strategy for those who want to lose weight."

Beyond the longer-term aim of clinical trials, the next stage will be to investigate the more lasting effects of strength training in mice. The team also plans to examine how the effects may differ between types of fat and between locations in the body.

Exercise has long been known to benefit the body. By clarifying more of the underlying details, however, scientists may establish which forms of exercise suit particular people best and how they can be optimised.

"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 Moura.

The research has been published in Life Sciences.

This article was fact-checked by Fiona MacDonald and edited by Fiona MacDonald. Although we take pride in our process, we are only human. If you notice an error, please let us know.