The Effect of Peanut Butter Overfeeding in Trained Men and Women: A Pilot Trial

Abstract

Introduction: It is known that consuming carbohydrate and fat calories above one’s daily needs affect body composition differently in comparison to protein. Thus, the purpose of this study was to determine how peanut butter overfeeding affects body composition in exercise- trained subjects.
Methods: 17 healthy exercise-trained men and women participated in the study. Subjects initially recorded their food intake via MyFitnessPal for a period of two weeks prior to coming to the laboratory in order to establish a baseline intake of energy and macronutrients. Subsequently, they came to the exercise science laboratory for body composition assessment via the Bod Pod® (i.e., weight, lean body mass, fat mass) and Impedimed® (i.e., total body water). Subsequently, they were instructed to consume 5 jars of peanut butter (Smuckers® Natural, 16 ounce jar) over the 4-week treatment period and were then post-tested. Results: Of the 17 subjects that participated in the study, 14 were compliant (i.e., actually consumed more total calories in comparison to baseline intake). Three subjects did not consume calories above their baseline intake. The 14 subjects that complied with the study consumed 6.4±4.6 jars (mean±SD) of peanut butter over the 4-week treatment period. Energy and fat intake increased (Kcals/day [p=0.0365]: Pre 2066±658 vs. Post 2592±1346, Fat grams/day [p=0.0361]: Pre 79±31 vs. Post 125±79). There were no significant changes in carbohydrate (grams/day: Pre 179±59 vs. Post 187±59) or protein intake (grams/day: Pre 160±110 vs. Post 179±136). The subjects’ fat mass significantly increased [p=0.0311] (Pre 11.7±6.0 vs. Post 12.5±5.2 kg) whereas body fat percentage showed a trend (p=0.0610) towards an increase (Pre 15.9±7.4 vs. Post 17.2±6.0 percent). There were no significant pre to post changes in body weight, lean body mass or total body water. Conclusions: Overfeeding on peanut butter (+500 kcal/day) results in an increase in body fat.