Exercise turns “bad” fat “good” Radha Chitale Exercise training helps develop fat that is more metabolically active than fat that results from sedentary behavior, according to two studies in mice and humans. The resulting “good fat” can lead to metabolic changes that improve glucose tolerance and control the effects of a fatty diet. “Exercise really can train your fat,” said lead author Dr. Kristin Stanford, a postdoctoral fellow at the Joslin Diabetes Center in Boston, Massachusetts, US. “Exercise training has beneficial effects on subcutaneous adipose tissue that contributes to improved systemic glucose homeostasis.” In the mouse study, mice were caged with or without an exercise wheel for 11 days. An analysis of their subcutaneous adipose tissue showed that the mice which exercised had smaller adipose cells with less lipid in each cell and the cells had more mitochondria, making them “browner” – more metabolically active. A group of 10 relatively fit men who exercised at high intensity 5 days per week for 12 weeks showed similar changes to their subcutaneous white adipose tissue (SWAT) in that it became “browner.” The men achieved at least a 10 percent increase in maximal aerobic capacity. A genetic analysis in the mice and men showed that a significant number of genes and metabolic pathways had changed, and more genes changed in the fat tissue than muscle tissue, which senior investigator Dr. Laurie Goodyear, of the Joslin Diabetes Center and Harvard Medical School in Boston, Massachusetts, US, said was a huge surprise. “You don’t need a lot of exercise to cause dramatic adaptations to subcutaneous adipose tissue,” she said. The mouse study carried on with transplanting the trained brown fat into sedentary mice which were given a high-fat diet. These mice had improved glucose tolerance and insulin sensitivity for 12 weeks of follow-up compared with sham-treated mice. The transplanted adipose tissue in these sedentary mice also appeared to neutralize the effects of a high-fat diet as there was no difference in body weight, and glucose levels remained lower than those in sham-treated mice fed normal or high-fat diets. Stanford hypothesized that the white adipose tissue produced secreted proteins responsible for improvements in glucose uptake, specifically in brown adipose and skeletal muscle tissues. Despite the apparent success of trained fat transplants in mice, Goodyear would not recommend similar procedures in humans, saying exercise was still the best way to achieve optimal fat levels. “I would argue that, in fact, the lack of exercise is just as important or maybe even more important than the increase in high-fat feeding and increased caloric consumption [leading to the] huge increase in rates of type 2 diabetes worldwide,” she said.
Posted on: Fri, 26 Jul 2013 16:14:59 +0000
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