Does exercise make us want to eat more high fat foods? The answer apparently depends on gender. Researchers at the University of Missouri, who worked with rats, not humans, have determined that exercise did make rats choose less high-fat food and more low-fat food, but only male rats. Female rats, yes, even those who exercised, continued to prefer high-fat foods. A U of Missouri news release reports that the researchers divided male and female rats into two groups—a sedentary group and one that had access to a running wheel, and they allowed both groups to eat the same food. After a week, the researchers replaced the standard diet with three optional diets: high fat (similar to cookie dough), high sucrose (three times more sucrose than the other two diets), and a high-cornstarch diet. All of the rats had continuous access to all three diets for four weeks. The researchers found that, while sedentary male rats preferred the high-fat diet over the other diets, the male runners ate about half as much of the high-fat diet as their sedentary counterparts but increased their intake of the other two options. Female sedentary rats, like their male counterparts, mostly stuck to the high-fat diet, but surprisingly, female runners also preferred the high-fat diet and actually consumed slightly more calories than the sedentary females.
“We also examined brain opioids and gut microbiota, and we discovered key changes that paralleled the patterns observed in diet preferences between male and female runners,” the researchers wrote. “A reason for this might be that females have an elevated threshold for rewards. Considering females demonstrate higher levels of reward signaling in the brain, this may possibly explain the higher threshold or capacity for reward. Perhaps something like running may be satiating for males but not for the females, so the females are consuming more of the high-fat diet. We expected to find differences between runners and sedentary rats, but it was the sex differences that surprised us.”