Is Non-Adherence Unique to Weight-Loss? Predictors of Adherence to a Heart-Healthy Diet in Lean vs. Obese Individuals

Detailed Summary

Background: \- Sticking to a diet plan can be difficult, but is important for many different health reasons. Some people seem to have a harder time following and sticking to a diet plan than others. It is not clear whether people of different weights (lean or obese) might have differences in the way they adhere to diet plans. Researchers want to study three different groups of people based on their body mass index (BMI), which measures people based on their weight and height. The study will place the participants on a 6-week diet and see how well they follow the diet. The information from this study may help develop better weight-loss plans and healthy diet ideas. Objectives: * To understand what factors affect adherence to a diet plan. * To collect information for future studies that may improve people's ability to stick to diets. Eligibility: \- Individuals at least 18 years of age who are lean (BMI between 18.5 and 25) or obese (BMI greater than 30). Design: * Participants will be screened with a physical exam and medical history. Blood and urine samples will be collected. They will have a full-body scan to measure fat and muscle. They will also answer questions on eating behaviors, mood, and desire to change eating patterns. * Participants will be separated into three groups. Each group will have a different diet. The lean group will have a heart-healthy diet designed to maintain the same weight. One of the obese groups will also have a heart-healthy diet designed to maintain the same weight. The other obese group will have a heart-healthy weight loss diet. In all groups, all food will be provided by the study doctors. Participants should not eat any food other than that provided for the study. * Everyone will start with a 1-week food testing period to find the right number of calories for each group. After this first week, participants will attend one diet counseling session per week and will be contacted randomly once a week to check on the foods they have had in the past 24 hours. Participants will complete daily food diaries on paper as well as daily food records using a smart phone. * Participants will come to the clinic twice a week to pick up the diet food. On one of those days, they will also have their counseling session. * The study will last for 6 weeks. At the final study visit, participants will repeat the tests from the screening study.

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