Objectives As 42.4% of the United States is obese and recent estimates expect an obesity/overweight prevalence of approximately three-fourths of the population by 2030, Americans have become more invested in finding weight control solutions. Commercial weight-loss programs and diets have risen to fulfill this need. However, there continues to be a lack of clarity surrounding the longitudinal and adverse outcomes of the majority of these programs. This report discusses a likely link between the usage of a popular commercial weight loss diet and the development of impaired kidney function in a 68-year-old patient. Methods Upon routine laboratory testing, the patient was noted to have elevated creatinine levels and was referred to a hematologist-oncologist for a bone marrow biopsy for a suspected diagnosis of multiple myeloma, and to a nephrologist for a kidney biopsy. The patient had a peak creatinine level of 3.02 mg/dL (reference range 0.70–1.25 mg/dL) prior to the kidney biopsy, which showed prominent calcium oxalate deposits and tubular atrophy with interstitial fibrosis, virtually excluding multiple myeloma. This finding placed the patient at risk for loss of kidney function, if not addressed immediately. Upon further investigation, the patient admitted to using a Nutrisystem® diet, which was aiding him in his weight loss goals. Results After a trial of removing this diet from his lifestyle, the creatinine level of the patient substantially improved to 1.42 mg/dL within three months, demonstrating a gradual improvement in kidney function. Conclusions This case report shows the importance of taking commercial weight-loss interventions into consideration when generating clinical recommendations for patients and adds to the currently limited literature on the long-term outcomes of the Nutrisystem® diet. Our findings point to the need for more comprehensive research into the effects of these programs and diets. Funding Sources Not applicable.