This phase 2 waitlist-controlled, randomized trial is designed to compare the difference in proliferative index (Ki67) between carbohydrate restricted diet and usual care over a 6 month period in men with prostate cancer who have been placed on Active Surveillance. Eligible patients include men over 18 years old, BMI >25, with their most recently performed biopsy pathologically confirming prostate adenocarcinoma who have been placed on AS. Arms of the trial will be randomized 1:1 in a crossover approach, with Arm A receiving a carb restricted diet over 6 months then SOC and Arm B receiving the waitlist control arm (i.e. SOC then allowed to go on diet after 6 months). Ki67 will be performed on tissue from the most recent biopsy at the beginning of the study and again on tissue obtained in the 6 month SOC biopsy. Every patient will be on the study for 12 months, and the study will continue for approximately 3.5 years.

Inclusion Criteria:

• Pathologically confirmed prostate adenocarcinoma
• Most recent biopsy positive for prostate cancer
• Currently on or starting active surveillance
• Ability to read, write, and understand English
• BMI >24 kg/m2
• Written informed consent obtained from subject and ability for subject to comply with the requirements of the study.
• Scheduled to undergo a prostate biopsy in 6 months as part of standard of care for their prostate cancer
• Age > 18 years

Exclusion Criteria:

• Already consuming a severely carbohydrate-restricted (i.e. <20g total carbohydrates per day) or vegetarian diet
• Medical comorbidities that in the opinion of the investigator limits the patient's ability to complete this study
• Anticipate needing prostate cancer therapy within the next 12 months (i.e. surgery, radiation, or hormonal therapy)
• Loss of >10% of body weight within the previous 6 months
• Currently receiving any oral hormonal therapy for prostate cancer or BPH (finasteride, dutasteride, bicalutamide)
• If prior oral hormonal therapy use for prostate cancer or BPH (as defined above), must not have been taking at time of prior biopsy and must be off for at least 3 months prior to study enrollment (oral medications)
• Having ever received any injection hormonal therapy or investigational vaccine for prostate cancer (LHRH agonist, LHRH antagonists, ProstVax, Provenge)
• Current use of weight loss medications including herbal weight loss supplements or enrolled in a diet/weight loss program