New study elucidates mechanisms behind metabolic benefits of fasting

A new study done on mice revealed how intermittent fasting (IF) improved metabolism and enhanced thermogenesis – the process of burning fat by generating body heat.
Previous research suggests that IF, where short periods without food are interspaced with periods of normal eating, may improve insulin sensitivity and counter weight gain in people with type 2 diabetes.
For the current study, Canadian researchers at The Hospital for Sick Children, in Ontario, placed groups of mice on a high-fat diet supplemented or not with IF for sixten weeks.
The IF cycle consisted in the mice being fed for two days, followed by one day without anything to eat. During the eating cycles, the IF mice were allowed to eat ad libitum.
Four months later, researchers found that the weight of intermittent fasting animals was significantly lower than that of mice on a normal eating pattern.
The fasted mice also showed improved glucose metabolism, as indicated by lower and more stable blood sugar levels and increased insulin sensitivity throughout the experiment. IF improved blood sugars and reduced body weight without changes in total caloric intake.
Additionally, the fasting regime increased the conversion of white fat into brown-like fat, which is more metabolically active and burns more calories.
Looking at what happened in the fat cells of mice more closely, researchers found that the beneficial effects of IF on fat burning could be attributed to higher thermogenesis.
They then went on to study what drove this increase in thermogenesis and found that fasting leads to an increase in what’s called the vascular endothelial growth factor (VEGF) in fat tissue.
The VEGF plays a key role in the browning of white fat and promotes good vascularisation and mitochondrial function in newly formed brown fat.
Further, the fasted mice displayed higher expression of the Ucp1 gene in brown fat, which is associated with enhanced thermogenesis and better insulin sensitivity.
Overall, these findings suggest that periodic bouts of IF seem particularly effective for weight loss and improving insulin sensitivity in mice.
Though most of the research on the benefits of IF has been done in animals, research is starting to be done in humans, and the results are similar to those seen in animals.
The findings were published in the journal Cell Research.