Habitual Diet and Avocado Trial

Non-contrast MRI scans will be performed to assess the volume of visceral adipose tissue. The outcome will be pre-post difference, compare the estimated mean change from baseline to follow-up in the 2 randomized groups with all tests of group differences performed according to the intent to treat.

Non-contrast MRI scans will be performed to assess hepatic lipid content/hepatic fat fraction.

Phlebotomy is performed after a minimum 8 hour fast. Specimens will be separated and aliquoted, and shipped for analysis to Tufts University site for: fasting total cholesterol, triglyceride, high density lipo-protein cholesterol (HDL-C), glucose and insulin. LDL will be calculated using the Friedewald equation unless fasting triglyceride levels are > 400 mg/dL in which case they will be measured using a direct LDL assay. There will be a comparison of the estimated mean change from baseline to follow-up with all tests of group differences performed according to intent to treat.

C-reactive protein (CRP) is a protein that the liver makes when there is inflammation in the body. Also called a marker of inflammation and can be measured with the hs-CRP test. Inflamed arteries puts individuals at greater risk of heart disease, heart attack, stroke and peripheral arterial disease. A fasting sample will be obtained, shipped to and analyzed at Tufts University for hsCRP.

Fasting RBC specimens shipped to Tufts University for analysis of RBC fatty acid profiles. The Fatty Acid Profile measures major fatty acids found in red blood cells.

Seated blood pressure will be measured at each visit (except the screening visit) utilizing automated devices as per a standardized protocol across all sites. Three measurements will be taken after a 5 minute rest period, 1 minute apart. The last two readings are averaged for analysis.

Participants will be weighed at all in-study visits using high quality digital scales commonly used in clinical practice and that are in good working order. Participants will be weighed in light street clothes without shoes. The same scale is used throughout the trial.

A measuring tape specifically designed for waist circumference (recommended brands include Gulick or Seca) will be used according to a standardized procedure outlined in the trial Manual of Procedures. Waist circumference will be used during screening to assess eligibility. Measurements will be taken against the skin at the approximate midpoint between the lower margin of the last palpable rib and the top of the iliac crest. Two measurements are obtained at each visit and averaged.

Questions regarding participant satisfaction with the diet and food intervention will be assessed by completing the Diet, Food and Avocado Satisfaction Questionnaire. The questionnaire will only be completed by participants randomized to consume one avocado a day. The questionnaire is completed within 24 hours of a clinic visit and can be self- or staff administered. It consists of 14 questions about eating and preparing avocados each having a 100 point Likert scale with responses of "Not at all" and "Extremely".

All participants will complete the RAND (research and development) 36-Item Health Survey to assess 8 health concepts: physical functioning, bodily pain, role limitations due to personal or emotional problems, emotional well-being, social functioning, energy/fatigue and general health perceptions.All items are scored so that a high score defines more favorable health state. Each item is scored on a 0 to 100 range so that the lowest and highest possible scores are 0 and 100. Items in the same scale are averaged together to create 8 scale scores. Items that are left blank are not taken into account when calculating scale scores.

The 20-item Short Form Health Survey (SF-20) was designed to reduce respondent burden while achieving minimum standards of precision for purposes of group comparisons involving multiple health dimensions. It includes 7 items to assess physical functioning, 2 items on role functioning, 1 social functioning survey item, 5 items to assess mental health, 4 items on current health perceptions and 1 item on pain. Participants in the control group will complete the RAND 20-Item Short Form Survey.

All participants will complete the Pittsburgh Sleep Quality Index questionnaire (PSQI) which is a self-rated questionnaire that assesses sleep quality and disturbances over a 1-month time time interval. 19 individual items generate seven "component" scores: subjective sleep quality; sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication and daytime dysfunction. The sum of scores for the 7 components yield one global score.

Four 24-hour dietary recalls will be conducted for each study participant during the course of the study. The goal for the 3 intra-study recalls is to capture intake data for 2 weekdays and 1 weekend day for each participant. The recalls are collected and analyzed using Nutrition Data System for Research (NDSR) software Vs 2017. The Loma Linda University site and Tufts University will be responsible for collecting 50% each of the 24 hour recalls across all study sites. They will follow a standardized manual of procedures for dietary data collection and dietary data management. Outcome data from NDSR will include daily estimated energy and nutrient intake, as well as food, food group and dietary supplement data.