Researchers at Baylor College of Medicine have found what they believe is a critical tuning dial for controlling whole body energy.
When energy levels within cells drop, it sets off a series of events designed to increase the amount of calorie-rich dietary fat that the body will absorb.
"Thousands of years ago, this would have been crucial," said Bert O'Malley.
The enzyme AMPK causes cells to consume less energy in the form of ATP and to produce more and also drives appetite.
Now, the study shows that AMPK also allows for the optimal absorption of the most energy-rich fuel from the diet: fat. However, this happens depending on its activation of SRC-2, a master control gene whose job is to switch other genes on.
Mice lacking SRC-2 fail to absorb fat normally, the study found.
"It's all about energy accretion, storage and delivery," O'Malley said.
However, this was all fine in times where food was scarce.
"It's designed to get in more fat. Over evolutionary time, when you didn't know when the next meal would be, you really couldn't get enough fat. Now, our next meal is at the corner McDonald's," O'Malley said.
The discovery may ultimately have important clinical implications, the researchers say.
"Obesity is all about fat absorption and storage. If you could turn that down, you could have a major effect on a disease that is slowly killing the population," O'Malley said.
He said his team is now conducting studies in search of SRC-2 inhibitors that might do exactly that.
The study appears in the January issue of Cell Metabolism.