Effects of Menthol on Weight Regain and Maintenance of Caloric Restriction: A Pilot Study

The prevalence of excessive weight gain (obesity) has steadily increased since about 1980. Excessive weight gain is associated with many comorbidities; thus, a successful treatment is needed. The most common form of non-surgical treatment for excessive weight gain is caloric restriction with the intent to reduce body weight by 10%. Though this treatment is successful at reducing body weight, it often fails at maintaining the weight loss. Dietary menthol has been suggested as a possible treatment for excessive weight gain and has produced promising results as a preventative method for excessive weight gain. Our studies aimed at reducing weight regain and maintaining caloric restriction by feeding male Sprague-Dawley rats 0.5% dietary menthol during a period of caloric restriction, aimed at reducing their body weight by 10%, following an experimental period where the rats were fed a high-fat diet (HFD) or low-fat diet (LFD). The effects of the dietary menthol were observed during the weight regain period following the caloric restriction period. Two studies were conducted, and both were unable to achieve a maintenance of weight loss following caloric restriction, although our first study was able to produce a delay in weight regain and did not show any evidence of increased thermogenesis in menthol-treated rats. Our findings differ from the findings of previous studies on dietary menthol which could possibly be due to species effects, differences in procedures, age effects, or effects of different fatty acid compositions. The contrasting results in our studies could be due to genetic differences between litters used or a difference in manufacturing of the menthol diet between studies. Given the partial response to menthol in the first study, it can be suggested that the concentration of 0.5% may be below the threshold of menthol sensitivity for some rats. Future research should focus on increasing the concentration of dietary menthol from 0.5% to 1%, since the current concentration did not yield a reduction in weight regain or maintenance of caloric restriction.