The body contains white fat, which stores lipids (known as triacylglycerides) as energy, and brown fat that burns these lipids to produce heat when the body is cold, a process known as thermogenesis.
Stores of brown fat are healthy but they decrease with age and in obese and diabetic individuals. Ways to activate thermogenesis in brown fat are therefore seen as potential preventative measures to obesity.
The nutrition and food supplement industry has invested big money into research projects to identify molecules that transform white fat into healthier brown fat. Resveratrol and mulberry extract have been suggested as potential activators in the past.
But scientists are now suggesting that whole foods, specifically a carbohydrate-rich meal, could also kickstart the process of brown fat burning the energy of triacylglycerides.
"Studies showed that participants who spent hours in the cold chamber daily not only experienced an increase in the heat output of brown fat in the cold as they got used to the lower temperatures, but also an improvement in the control of blood sugar via insulin," said Professor Martin Klingenspor, head of the chair for molecular nutritional medicine at the Technical University of Munich (TUM) and co-author of the experiment.
In this study, the researchers claim to have shown “for the first time” that heat generation in brown adipose tissue could be activated by a test meal “just as it would be by exposure to cold”.
"We now know that the activation of brown adipose tissue could be linked to a feeling of being full," said Klingenspor, however further studies are needed to determine if this energy is simply lost or whether it has another function.
The researchers tested a group of 25 male and female individuals for markers of thermogenesis before and after two conditions: being exposed to the cold and after eating a meal that contained 58 % carbohydrates, 25% fat and 17% protein.
These markers included the absorption of glucose and fatty acids, but also the oxygen consumption in brown fat, measured using indirect calorimetry, positron emission tomography and computer tomography.
“A single meal, dominant in carbohydrates and comprising all macronutrients, can stimulate brown adipose tissue (BAT) thermogenesis,” the researchers wrote. “Although human cervico-thoracic BAT appears to have a minor thermogenic potential compared with whole-body thermogenesis in postprandial state, the magnitude of BAT postprandial thermogenesis is almost equivalent to cold activation.”
Source: Cell Metabolism
“Postprandial Oxidative Metabolism of Human Brown Fat Indicates Thermogenesis”
Published online ahead of print, https://doi.org/10.1016/j.cmet.2018.05.020
Authors: Mueez U Din, Teemu Saari, Juho Raiko, Olof Solin, Pirjo Nuutila, Kirsi A. Virtanen