Patient must have adequate nutritional status with Body Mass Index (BMI) > 18 kg/m^2 and body weight of > 40 kg with serum albumin > 3 g/dL. BMI >= 27 kg/m^2 documented within 56 days prior to study registration; the most recent body mass index (BMI) obtained must be used for eligibility; if most recent BMI is < 27 then the patient is not eligible to enroll Patients with a body mass index (BMI) > 35, < 20 Body mass index (BMI) > 20 BMI 18 to 32 kg/m2. Patient must have adequate nutritional status with Body Mass Index (BMI) > 18 kg/m^2 and body weight of > 40 kg with serum albumin > 3 g/dL. Body mass index (BMI) is >= 18.5 BMI >35 Body mass index (BMI) > 25 at study entry Patients must be eligible to undergo a ketogenic or Atkins based diet according to baseline body mass index (BMI), comorbid medical conditions, and baseline laboratory assessment Body mass index (BMI) < 20.0 Body mass index (BMI) < 17.5 BMI >= 25 kg/m^2 Body mass index (BMI) >= 21 at time of study enrollment BMI < 21 at time of study enrollment Body mass index (BMI) >= 21 BMI < 21 at time of study enrollment Body mass index (BMI) >= 35 mg/m^2 =< 56 days prior to registration Body mass index (BMI) > 35% will be considered on a case-by-case basis by the Radiation Oncology principal investigator (P.I.) Patients who are significantly below their ideal body weight (body mass index [BMI] < 17) Patients with a body mass index (BMI) of 40 or more Subjects with known severe claustrophobia or with body habitus not compatible with the bore (> 300 lbs, body mass index [BMI] > 40) may also have to be excluded Body mass index (BMI) > 35 Body mass index (BMI) > 30% will be considered on a case-by-case basis by the radiation oncology principal investigator (PI) Body mass index (BMI) >= 18.5 Body mass index (BMI) <18.5 or >35 kg/m2. Creatinine level < 1.0 x ULN or creatinine clearance ? 60 mL/min/1.73 m^2 for patients with creatinine levels above or below the institutional normal (as determined by Cockcroft-Gault equation). For patients with a Body Mass Index (BMI) > 30 kg/m^2, lean body weight should be used to calculate the GFR. Body mass index (BMI) >= 21 BMI < 21 Have initial body mass index (BMI) >= 27.0 kg/m^2 and =< 40 kg/m^2 Body mass index (BMI) < 18 or > 35 Patient’s body mass index must be 30 kg/m^2 or higher The donor has a BMI of more than 18.5 and less than 35.0 kg/m2. DONOR: Body mass index (BMI) =< 35 Has BMI > 34.9 kg/m2. Body mass index (BMI) of 18-30 Patients who are severely underweight (body mass index [BMI] less than 17) or patients with a body surface area (BSA) < 1.4 m^2 as calculated per Dubois 1916 or Mosteller 1987 Has BMI > 34.9 kg/m2 Body mass index (BMI) > 40 Body mass index ? 35 Body mass index > 40 kg/m² Body mass index equal to or greater than 35 Women of any body mass index (BMI) undergoing a laparotomy procedure for a presumed gynecologic malignancy Body mass index (BMI) > 40 kg/m^2 Body mass index (BMI) >= 18.5 Are overweight or obese with the following criteria (determined by study team at eligibility screening): body mass index (BMI) > 25 kg/m^2 (calculated using height and weight; an upper limit BMI will not be set; we will rely on obtaining physicians’ clearance to assess full eligibility) or body fat > 30% (estimated by bioelectrical impedance), and waist circumference > 35 in Body mass index (BMI) >= 30 kg/m^2 BMI =< 29.9 kg/m^2 Body mass index of 30.0 – 49.9 and body weight < 300 pounds Body mass index (BMI) >= 36 kg/m^2 Body mass index (BMI) >= 20 kg/m^2 Patients with a body mass index (BMI) > 40 Body mass index (BMI) < 30 kg/m^2 Body mass index (BMI) (26 - 40 kg/m^2) Patient is obese (body mass index [BMI] >= 30 kg/m^2) Body mass index (BMI) >= 25 kg/m^2; and Body mass index (BMI) < 35 Participants must have a body mass index (BMI) of 24.45 or higher as assessed in the medical record Body mass index (BMI) < 18.5 or > 35 kg/m^2 will be excluded Body mass index (BMI) >= 22 kg/m^2 BMI < 25 kg/m^2 Body mass index (BMI) =< 35 Obese – defined as a body mass index (BMI) >= 35 kg/m^2 as calculated in the Epic computer record Body mass index (BMI) of 25-33 kg/m^2 Subjects who are underweight (defined as a body mass index [BMI] < 17.5) Body mass index (BMI) >= 25 kg/m^2 Body mass index (BMI) > 40 (morbid obesity) Body mass index (BMI) > 35 Body mass index (BMI) > 45 or < 17 Body mass index (BMI) between 18 and 35 kg/m^2 Body mass index (BMI) >= 30 Body mass index (BMI) > 20 Body mass index (BMI) greater than or equal to 30 kg/m^2 BMI less than 30 kg/m^2 Body mass index (BMI) 30- < 45 kg/m^2 Patients with body mass index (BMI) less than 18.5 and/or score in the “severe malnourished” category of the patient generated subjective global assessment (PGSGA) will be excluded Overweight (body mass index [BMI] >= 30) BMI >= 30 Patients with a body mass index (BMI) > 40 (obese class III criteria) The subject has a body mass index (BMI) > 35 Body mass index (BMI) > 30 kg/m^2 BMI < 30 kg/m^2 Body-mass index less than 18.5 (kg/m^2) Subjects who have a body mass index (BMI) over 40 Body mass index (BMI) >= 40 Phase 2 only: be overweight or obese (i.e., have a body mass index [BMI] > or = 25 kg/m^2) Obesity (body mass index [BMI] >= 30 kg/m^2) Patients with body mass index (BMI) < 20 kg/m^2 Body mass index (BMI) < 25 Body mass index (BMI) < 18.5 Kg/m^2 Body Mass Index (BMI) >= 30 kg/m^2. Has a current measured BMI less than 30 kg/m^2. Body mass index (BMI) 25-40 kg/m^2 Body mass index (BMI) > 30 kg/m^2; women with a BMI > 45 kg/m^2 must be age < 60 and ability to perform physical activity must be confirmed Body mass index (BMI) 30-45 kg/m^2 Body mass index (BMI) > or equal to 25 kg/m^2 BMI 25-40 kg/m^2 Body mass index (BMI): < 36 kg/m^2 Have a body mass index (BMI) of 25 kg/m^2 or greater and weight =< 400 lbs PILOTS I AND II: Body mass index (BMI) of 25 or higher OR < 150 minutes of moderate to vigorous exercise per week OR < 5 servings of fruit and vegetables per day A body mass index (BMI) >= 25 as assessed in the medical record and have intact breasts and ovaries Body mass index (BMI) 25-45 kg/m^2 Body mass index under 19 or over 45 Body mass index (BMI) < 40 kg/m^2 Body mass index (BMI) between 30 - 40 Body mass index (BMI) above 45 kg/m^2 Overweight or obese (body mass index [BMI] of 24 or greater) Body mass index (BMI) >= 25 kg/m^2 Have a body mass index (BMI) between 30.0 kg/m^2 and 45.0 kg/m^2 Subjects with a body mass index (BMI) of ? 34; Any body mass index (BMI) Subjects must have a body mass index (BMI) of 25-40 Body mass index (BMI) >= 24 kg/m^2 Have a body mass index (BMI) of 25 kg/m^2 or greater Participants must have a body mass index (BMI) >= 25, defined as (weight in kilograms/[height in meters]^2) Patients must have a body mass index (BMI) >= 25.0 as calculated by the formula: weight in pounds / height squared x 703 = BMI; a BMI of:\r\n* 18.5-24.9 is considered normal;\r\n* 25.0-29.9 is considered overweight;\r\n* 30.0+ is regarded as obese Body mass index (BMI) > or = 30 kg/m^2 Overweight or obese (body mass index [BMI] >= 25.0 kg/m^2) BMI ? 24 kg/m2. Body mass index (BMI) overweight-obese: 25.0 - 40 kg/m^2 Body mass index < 35 kg/m^2 Body mass index (BMI) between 25-35 The patients has a body mass index (BMI) >40, Body mass index (BMI) < 35 kg/m^2 Body mass index (BMI) >= 30 HEALTHY VOLUNTEER: Must have a body mass index (BMI) greater or equal to 19 and less than or equal to 33 Body mass index (BMI) > 35 Patients exceeding the weight limitations of the scanner or are not able to enter the bore of the PET scanner due to body mass index (BMI) Patients exceeding the weight limitations of the scanner or are not able to enter the bore of the PET/CT scanner due to body mass index (BMI) Patients exceeding the weight limitations of the scanner or are not able to enter the bore of the PET/CT scanner due to body mass index (BMI) Body mass index (BMI) > 35 (patients who may not fit on a 35 x 35 detector) Patients with body mass index (BMI) greater than 34 or less than 16 Body mass index (BMI) 25-45 kg/m^2 Have a body mass index (BMI) > 30 Body mass index (BMI) greater than or equal to 40 or less than or equal to 17 kg/m^2 at screening visit Body mass index of 30 or greater Initial body mass index (BMI) >= 30.0 kg/m^2 and < 40 kg/m^2 Patients with a lower body mass index (BMI) (BMI < 18) will be excluded Body mass index is >= 25 kg/m^2 Patients with body mass index greater than 40 kg/m^2