We've all had those days, sometimes even weeks, when we find ourselves endlessly hungry. When it takes a lot of food to fill you up.

That was me earlier this week. In a single day I ate two breakfasts, lunch, an afternoon snack, came home from work feeling so starved that I practically ate a whole dinner just "snacking" on what I was cooking for dinner-and then ate dinner. I like to eat, but this was so excessive I began to search for a reason: Am I pregnant? Could I have developed an overactive thyroid overnight? The hypochondriac in me had a field day, until, duh(!), I remembered a recent study that we covered in EatingWell: splurging on greasy, fatty foods can rev your appetite for days afterwards.

These findings, published in the Journal of Clinical Investigation, explained exactly why I was feeling extra hungry-my husband and I had just spent a long weekend in New York City eating (ahem, gorging!) our way through town. (Next time you eat to much, try these 3 foods to eat when you overeat.)

Here's what the researchers did: they gave two types of fat to mice (in addition to their regular diets). One was palmitic acid, a saturated fat found in beef, butter, cheese and palm oil. The other, oleic acid, is a healthier fat common in olive oil, fish, nuts and soybeans.

After three days of palmitic acid, mouse brains became resistant to the appetite-suppressing hormones leptin and insulin. Other work in humans suggests that the same holds true for people, says lead author Deborah Clegg, Ph.D., R.D., at the University of Texas Southwest Medical Center in Dallas. She also added that these findings hearken back to a time when our ancestors had to feast on fatty foods, such as meat, whenever it became available because they didn't know when the next successful hunt would come.

Now I understood why I was so darn hungry. How was I going to get back on track? I started with some exercise because that always makes me feel better. (Try these 6 tips for sneaking in your exercise.) And I tried Dr. Clegg's recommendations for getting back on track: