Objective: This research examined the impact of daily ingestions of commercial high protein nutrition bars (with or without added fiber) on 24-h energy intake and satiety for one week among free-living young healthy adults. Design: In a 4-week double-blind, randomized crossover trial, 21 normal and overweight participants (Mean BMI 23.9 ± 2.7 kg/m²), free of chronic diseases, were randomized assigned to HP (high protein: 21 g protein) or HPHF (high protein high fiber: 20g, 14 g fiber) nutrition bars. Participants were included in the trial if they meet the criteria for non-smoking, and not taking prescribed medication for chronic diseases. Participants were instructed to consume commercial nutrition bars daily for seven consecutive days. Body composition was measured with a bioelectrical impedance scale at weeks 1, 3, and 5. Dietary data was recorded by the MyFitnessPal app on Wednesday, Friday, and Sunday of each week. Results: The mean energy intake for the weeks HPHF bars were consumed is significantly higher compared to baseline (1998 ± 534 vs. 1806 ± 537 respectively; p = 0.035). The mean fat mass following one week of HPHF bar consumption was significantly higher than the baseline value (18.8 ± 6.8 vs. 18.3 ± 6.7 respectively; p = 0.023) and trended higher (18.8 ± 6.8 vs. 18.3 ± 6.7 respectively; p = 0.057) in comparison to the value following one week of HP bar consumption. For the high physical activity level group (n = 10), the mean energy intakes for the baseline week and the weeks the HP and HPHF bars were consumed were 1883 ± 597 kcal, 2154 ± 712 kcal, and 2099 ± 603 kcal respectively (p ˂ 0.04; energy intakes for both bars were significantly different from baseline). Nutrient intakes differed significantly mirroring the nutrient profile for each specific bar. There are significant effects after both bars on satiety, but there were no differences between each bar. Conclusions: Sales of nutrition bars gained rapid growth and may represent a unique source for specific nutrients. However, ingestion of commercial high protein nutrition bars may increase the risk of gaining fat mass and eventual body mass over time.