Phenolic-enriched raspberry fruit extract (Rubus idaeus) resulted in lower weight gain, increased ambulatory activity, and elevated hepatic lipoprotein lipase and heme oxygenase-1 expression in male mice fed a high-fat diet.

Red raspberries (Rubus idaeus) contain numerous phenolic compounds with purported health benefits. Raspberry ketone (4-(4-hydroxyphenyl)-2-butanone) is a primary raspberry flavor phenolic found in raspberries and is designated as a synthetic flavoring agent by the Food and Drug Administration. Synthetic raspberry ketone has been demonstrated to result in weight loss in rodents. We tested whether phenolic-enriched raspberry extracts, compared with raspberry ketone, would be more resilient to the metabolic alterations caused by an obesogenic diet. Male C57BL/6J mice (8 weeks old) received a daily oral dose of vehicle (VEH; 50% propylene glycol, 40% water, and 10% dimethyl sulfoxide), raspberry extract low (REL; 0.2 g/kg), raspberry extract high (REH; 2 g/kg), or raspberry ketone (RK; 0.2 g/kg). Coincident with daily dosing, mice were placed on a high-fat diet (45% fat). After 4 weeks, REH and RK reduced body weight gain (approximately 5%-9%) and white adipose mass (approximately 20%) compared with VEH. Hepatic gene expression of heme oxygenase-1 and lipoprotein lipase was upregulated in REH compared with VEH. Indirect calorimetry indicated that respiratory exchange ratio (CO₂ production to O₂ consumption) was lower, suggesting increased fat oxidation with all treatments. REH treatment increased total ambulatory behavior. Energy expenditure/lean mass was higher in REH compared with REL treatment. There were no treatment differences in cumulative intake, meal patterns, or hypothalamic feed-related gene expression. Our results suggest that raspberry ketone and a phenolic-enriched raspberry extract both have the capacity to prevent weight gain but differ in the preventative mechanisms for excess fat accumulation following high-fat diet exposure.