The study will investigate the effect of avocado consumption on markers of vascular health. Sixty participants will be enrolled in the 6-week study. A randomized parallel design will be utilized. Participants will either receive a typical American diet, or a modified typical American diet in which avocado is substituted for foods that contain moderate and high amounts of saturated fat, to allow the isoenergetic inclusion of avocado.

Inclusion Criteria:

• BMI between 25 and 42 kg/m2
• Age 28 to 70 years during the intervention
• Fasting glucose ≤ 126 mg/dl
• Blood pressure ≤ 160/100 mm Hg

Exclusion Criteria:

• Presence of kidney disease, liver disease, gout, certain cancers, thyroid disease, gastrointestinal, other metabolic diseases, or malabsorption syndromes
• Women who have given birth during the previous 12 months
• Pregnant women or women who plan to become pregnant or become pregnant during the study
• Lactating women
• Type 2 diabetes requiring the use of oral antidiabetic agents or insulin
• History of eating disorders or other dietary patterns which are not consistent with the dietary intervention (e.g., vegetarians, very low fat diets, high protein diets)
• Volunteers who routinely participate in "heavy" exercise or volunteers who initiate an exercise program during the study.
• Volunteers who have lost 10% of body weight within the last 12 months
• Use of prescription or over-the-counter antiobesity medications or supplements (e.g., phenylpropanalamine, ephedrine, caffeine, during and for at least 6 months prior to the start of the study) or history of a surgical intervention for obesity
• Active cardiovascular disease (such as heart attack or procedure within the past three months or participation in a cardiac rehabilitation program within last three months, stroke or history/treatment for transient ischemic attacks in the past three months, or documented history of pulmonary embolus in past six months)
• Smokers or other tobacco users (during the 6 months prior to the start of the study)
• Unable or unwilling to give informed consent or communicate with study staff
• Self-report of alcohol or substance abuse within the past twelve months and/or current acute treatment or rehabilitation program for these problems (Long-term participation in Alcoholics Anonymous is not an exclusion.)
• Other medical, psychiatric, or behavioral factors that in the judgment of the Principal Investigator may interfere with study participation or the ability to follow the intervention protocol.