Reduced Carbohydrate Versus Fat in Obese Subjects
Condition: Obesity
MeSH terms: Obesity
Intervention: Reduced fat diet; Reduced carbohydrate diet; Drug: f-18 fallypride; fMRI; PET
Intervention description: RF (selective reduction of 85% of baseline fat calories per day); RC (selective reduction of 60% of baseline carbohydrate calories per day); Dopamine D2 receptor availability is measured by positron emission tomography (PET) using the positron emitting compound [18F] fallypride which binds competitively with dopamine to the D2 receptor.; Functional MRI (fMRI) will be used to measure the effects of diet and weight loss on regional brain activity; Positron emission tomography (PET) will be used to assess whether To assess whether brain activity and reward pathways are altered
Intervention MeSH terms: Fallypride
Phase: Phase 2
Study type: Interventional
Primary purpose: Treatment
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Enrollment: 43.0
Sex: All
Minimum age: 18 Years
Maximum age: 45 Years
Healthy volunteers: No
Keywords: Obesity; Weight Loss; Carbohydrate; Fat; Macronutrient Balance; Healthy Volunteer

Summary:

      Popular weight loss strategies often involve reducing an individual's consumption of
      carbohydrates or fat. However, no controlled study has been carried out to evaluate the
      effects of reducing carbohydrate versus fat consumption while keeping the other nutrients at
      standard levels to maintain an individual's weight. Researchers are interested in
      investigating how different restrictions of carbohydrates or fats affect the many processes
      involved in weight loss, including brain activity and blood and brain chemical composition.
    

Eligibility criteria:

        -  INCLUSION CRITERIA:

          -  Age 18-45 years, male or female

          -  Body mass less than 350 lbs. (max. weight dictated by table limit for functional
             magnetic resonance imaging (fMRI) scanner) when acquisition of large bore fMRI is
             complete, max. wt. limit will increase to 400 lbs.

          -  Weight stable (less than plus or minus 5 kg over past 6 months)

          -  Body mass index greater than or equal to 30.0 kg/m(2)

          -  Premenopausal (women only)

          -  Healthy, as determined by medical history and laboratory tests

          -  Able to complete daily bouts of walking at a moderate rate

          -  Written informed consent

        EXCLUSION CRITERIA:

          -  Body mass greater than 350 lbs. (max. weight dictated by table limit for fMRI scanner)
             when acquisition of large bore fMRI is complete, max. wt. limit will increase to 400
             lbs.

          -  BMI less than 30.0 kg/m(2)

          -  Evidence of metabolic or cardiovascular disease, or disease that may influence
             metabolism (e.g. cancer, diabetes, thyroid disease)

          -  Taking any prescription medication (except birth control) or other drug that may
             influence metabolism (e.g. diet/weight-loss medication)

          -  Hematocrit less than 34% (women only)

          -  Hematocrit less than 40% (men only)

          -  Pregnancy, lactation (women only)

          -  Allergy to lidocaine or ethanol

          -  Participating in a regular exercise program (greater than 2h/week of vigorous
             activity)

          -  Caffeine consumption greater than 150 mg/day (will be clamped at baseline intake
             during study)

          -  Regular use of alcohol (greater than 2 drinks per day), tobacco (smoking or chewing),
             amphetamines, cocaine, heroin, or marijuana over past 6 months

          -  Past or present history of eating disorder (including binge eating) or psychiatric
             disease

          -  Volunteers with strict dietary concerns (e.g. vegetarian or kosher diet, multiple food
             allergies)

          -  Are claustrophobic to a degree that they would feel uncomfortable in the MRI machine.

          -  Having any metal in their body (for example, pacemakers, metallic prostheses such as
             cochlear implants or heart valves, shrapnel fragments, etc.).

          -  Left-handedness

          -  Non-native English speakers

          -  Volunteers unwilling or unable to give informed consent

        Control Subjects

        INCLUSION CRITERIA:

          -  Age 18-45 years, male or female

          -  18.5 kg/m(2) less than BMI less than 25.0 kg/m(2)

          -  Weight stable (less than plus or minus 5 kg over past 6 months)

          -  Premenopausal (women only)

          -  Healthy, as determined by medical history and laboratory tests

          -  Written informed consent

        EXCLUSION CRITERIA:

          -  BMI less than 18.5 or greater than 25.0 kg/m(2)

          -  Evidence of metabolic or cardiovascular disease, or disease that may influence
             metabolism (e.g. cancer or diabetes)

          -  Taking any prescription medication (except birth control) or other drug that may
             influence metabolism (e.g. diet/weight-loss medication)

          -  Hyperlipidemia (fasting plasma triglyceride concentration greater than 150 mg/dl)

          -  Hematocrit less than 34% (women only)

          -  Hematocrit less than 40% (men only)

          -  Pregnancy, lactation (women only)

          -  Participating in a regular exercise program (greater than 2h/week of vigorous
             activity)

          -  Caffeine consumption greater than 150 mg/day

          -  Regular use of alcohol (greater than 2 drinks per day), tobacco (smoking or chewing),
             amphetamines, cocaine, heroin, or marijuana over the past 6 months

          -  Past or present history of eating disorder (including binge eating) or psychiatric
             disease

          -  Volunteers with strict dietary concerns (e.g vegetarian or kosher diet, multiple food
             allergies)

          -  Are claustrophobic to a degree that they would feel uncomfortable in the MRI machine.

          -  Having any metal in their body (for example, pacemakers, metallic prostheses such as
             cochlear implants or heart valves, shrapnel fragments, etc.).

          -  Left-handedness

          -  Non-native English speakers

          -  Volunteers unwilling or unable to give informed consent