Many of us spend our lives fighting our tendency to gain weight. So, it is good news when something that many of us do already might be helpful in that struggle.
British researchers have suggested that drinking coffee appears to cause activation of brown adipose tissue or brown fat, which may help many people with obesity and diabetes.
They conducted a series of experiments in stem cell-derived fat cells (adipocytes) and found that caffeine exposure increased mitochondrial numbers and activity, as well as gene expression linked to “browning” of fat cells.
Next, in a small number of young healthy volunteers, they used thermal imaging to measure temperature changes in the neck (where the greatest abundance of brown fat is found) in response to drinking coffee or water.
The results showed that coffee drinking was followed by significant increases in temperature in that area relative to the body surface temperature.
This is the first study in humans to show that something like a cup of coffee might have a direct effect on brown fat functions. But there are many questions to be explored. Among other issues, thermal imaging is not a proven method for measuring changes in brown fat activity. Also, it is unclear whether caffeine is acting as the stimulus or if there is another component of coffee helping with the activation of brown fat.
Mitochondria are energy-producing parts inside the cells. Adaptive thermogenesis, which is the production of heat in response to environmental or dietary factors, occurs in the mitochondria of brown fat. The latter is functionally distinct from white fat, which predominates in obesity and is primarily concerned with energy storage.
Until relatively recently, it was thought that brown fat in humans existed only in babies. But 10 years ago, three papers were published reporting that some adults had small pockets of brown fat, which is brown because of the mitochondrial content, in the area of the neck above the collarbones and in abdominal areas.
However, the amount of brown fat decreases with age and decreases as body mass index (BMI) increases. So, senior citizens and very obese people have little or no brown fat.
For the new study, the researchers used human stem cell-derived fat cells that were exposed to caffeine, which showed evidence of increased cell metabolism including increased oxygen consumption and proton leak.
These functional responses were associated with browning-like structural changes in mitochondrial and lipid (fat) droplet content.
Next, the researchers studied nine healthy volunteers who had not engaged in vigorous exercise or consumed caffeine, drugs or alcohol for at least nine hours, and who had not eaten for at least two hours.
The volunteers underwent thermal (heat) imaging of the neck above the collarbone before and after consumption of either instant coffee or water alone, both heated to the same temperature. The results showed that drinking coffee led to a significant increase in temperature in the region, while no significant temperature changes were recorded following water consumption.
In view of the lab findings of the effects of caffeine on the fat cells noted above, they suggested that adult humans consuming caffeine may cause an increase in brown fat activity following a relatively the low dose of caffeine from a single standard cup of coffee.
They propose further intervention studies be undertaken to assess whether caffeine-induced brown fat activation in humans is dose-dependent, to refine the minimum intake required for a brown fat response, and explore whether comparable effects are seen in fully differentiated fat cells and primary cells, as well as in diabetic and/or obese individuals. So, there is still a lot to be studied.
There have been previous studies showing that the combination of caffeine with other things can promote weight loss. However, neither caffeine alone, nor coffee, have been shown to have this effect.
Also, coffee drinkers seem to live longer, but we do not know why that occurs. Previous studies do not seem indicate that caffeine is the answer. So, it may be just because coffee drinkers also do other healthy things, like exercise and eat well.
We should be careful to avoid making too much fuss about increased brown fat function, since it has also been shown to happen with cold exposure. If increased brown fat function was all you needed to lose weight, then we could all just go into a cold climate or into a refrigerator and lose weight. But that has not been shown to work.
For now, being a coffee drinker myself, I will just be happy that the studies seemed to be in favor of coffee drinking and hope the next studies will be as well.