Background:

Diet is one of the most modifiable behaviors affecting health. But diet assessment measures that are based on self-report can be inaccurate. Researchers want better ways to address the role of diet in chronic disease. They want to see if stable isotopes can be used to better assess what people eat.

Objective:

To see if stable isotopes can help scientists identify things people eat.

Eligibility:

Healthy adults ages 18 to 65

Design:

Participants will be screened with a medical history and physical exam. They will have blood and urine tests. These tests will be repeated during the study.

Participants will stay in the inpatient unit of the NIH in Phoenix, Arizona, for 13 weeks.

For 7 days, participants will eat a diet prepared by the NIH kitchen. They will get balanced meals that are 50% carbohydrates, 20% protein, and 30% fat. Then participants will be randomly placed on one of 3 diets containing different percentages of carbohydrates from soda.

Participants height and weight will be measured. The amount of fat and muscle in their body will be measured by body scans that are similar to x-rays.

Participants will have oral glucose tolerance tests. They will consume a sugar drink and then give blood samples over 3 hours.

Participants will give hair and stool samples.

Participants will complete a diet questionnaire. It assesses their food intake over 24 hours.

Participants will complete behavioral questionnaires and computer performance tests.

Participants will have fat biopsies taken from their stomach and thigh.

Participants will have three 24-hour stays in a metabolic chamber. It is used to measure metabolism.

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Study Description:

This study will be an inpatient study in which highly specific diets will be fed to volunteers for approximately 12 weeks and stable isotopes will be measured in blood, hair, and adipose. Ultimately, the goal is to develop biomarkers to be used to validate food intake patterns in outpatient clinical and epidemiological studies.

Objectives:

The primary objective of this study is to validate the use of stable isotope biomarkers as representatives of specific dietary intake patterns.

Secondary objectives include evaluation of the effect of the amount of soda on urinary sucrose and fructose excretion, extracellular vesicles levels and content, and gut microbiota.

Endpoints (Outcomes):

Primary Endpoints: Primary Endpoints: Changes in the blood, hair, and adipose carbon (13C/12C) and nitrogen (15N/14N) stable isotope ratio from baseline to 12 weeks.

Secondary Endpoints: Changes in urinary sucrose and fructose excretion, extracellular vesicles levels and content, gut microbiota from baseline to 12 weeks.

• INCLUSION CRITERIA:

In order to be eligible to participate in this study, an individual must meet all of the following criteria:

• Body mass index less than or equal to 35 kg/m^2 to minimize the impact of body size on isotope measurements.
• Women and men between the ages of 18-65 years will be recruited for this study
• Healthy, as determined by medical history, physical examination, and laboratory tests.

EXCLUSION CRITERIA:

An individual who meets any of the following criteria will be excluded from participation in this study:

• Fasting plasma glucose greater than or equal to 126 mg/dL
• Alopecia totalis or inability to grow hair (at least one inch of hair required to obtain sample)
• Use of medication affecting metabolism and appetite in the last three months
• Medically- or self-imposed dietary restrictions that would limit a participant s ability/willingness to consume the diet to which they are randomized
• Current pregnancy, pregnancy within the past 6 months or currently lactating
• History or clinical manifestations of acute or chronic disorders or conditions that may affect appetite or EE, (such as, but not limited to type 1 or type 2 diabetes, Cushing s disease, thyroid disorders, coccidiomycoses)
• Gastrointestinal disease, including inflammatory bowel diseases (e.g. Chron s disease and ulcerative colitis), malabsorption syndromes (e.g. celiac disease), gastric ulcer (active) which may alter metabolism or absorption of study food
• Current, unstable medical conditions such as hepatitis, renal insufficiency, cancer requiring treatment in the last 5 years (except for nonmelanoma skin cancers or cancers that have clearly been cured), or central nervous system disorders etc. as assessed by history and physical exam
• Diagnosis of binge eating disorder, anorexia-nervosa, or bulimia-nervosa
• Evidence of alcohol abuse as defined by greater than or equal to 8-point score on the Alcohol consumption screening AUDIT questionnaire in adults
• Current use of tobacco products that exceed Low Dependence on the Fagerstrom Test for Nicotine Dependence Tool (score greater than 2)
• Current use of drugs such as amphetamines, cocaine, or heroin
• Any condition not specifically mentioned above that, in the opinion of the investigator, may interfere with the study or prove unsafe for participation.
• Weight change of plus or minus 5% in the last 3 months, per self report.
• Non-English speaking
• Inability of participant to understand and the unwillingness to sign a written informed consent document.

Conditions not specifically mentioned above may serve as criteria for exclusion at the discretion of the investigators. Additionally, potential subjects might be excluded if they demonstrate a style of interpersonal relationships that would inhibit successful completion of the study.

Non-English-speaking subjects as a population will be excluded from participation in this protocol. One of the secondary hypotheses of the protocol relates to a battery of psychological questionnaires and performances tests which are administered to the volunteers at the beginning and end of the study. There are currently no validated, translated forms of these questionnaires and tests available; therefore, we will restrict enrollment to English speaking subjects only.