For the study, researchers from Purdue University and the Federal University of Vicosa in Brazil put 15 obese women through three experiments: In the first, they ate 1.5 ounces of peanuts with orange juice and Cream of Wheat cereal. In the second, the same women swapped the peanuts out for 3 tablespoons of peanut butter. Finally, in the last experiment, they had only the juice and cereal (researchers adjusted the portion sizes so that calorie counts remained the same throughout all three phases).
After each experiment, researchers took participants’ blood samples and asked them to rate their appetite levels. Turns out, those who ate peanuts in the a.m. reported feeling fuller eight to 12 hours after breakfast—and peanut butter had an even stronger appetite-suppressing effect.
The results of the blood work indicate a couple of reasons why this might be the case, says Richard Mattes, PhD, professor of food and nutrition at Purdue University: For one thing, participants who ate peanuts had higher levels of peptide YY, a hormone that makes you feel full after eating (levels of the hormone were even higher in participants who ate peanut butter). When the women had eaten peanuts or peanut butter with breakfast, their blood sugar levels also spiked less after they had a carb-heavy lunch.
Ready to sprint to the closest grocery store and load up your cart with peanut butter? Not so fast. While peanut butter packs a ton of good-for-you nutrients like magnesium, zinc and vitamin E, it also comes with a fairly high calorie and (healthy) fat count. To reap peanut butter’s hunger-squashing benefits—without overdoing it in the calorie department—Mattes suggests limiting yourself to a two-tablespoon serving with breakfast.