It has been shown that large fat cells are associated with more risks for insulin resistance and more cardiovascular risk factors such as high cholesterol or triglycerides.

This study will look at fat cell size and how it affects fat deposition, insulin resistance and muscle oxidative capacity. A comparison will be made with the differences between participants with larger versus smaller fat cells in insulin resistance and blood levels of lipids. The study will also determine if characteristics of fat cells and muscle can predict the development of weight gain-induced insulin resistance.

Inclusion Criteria:

• Your Body Mass Index (height to weight ratio) is 22.5 to 32.5 (inclusive).
• You are 18-40 years of age.
• You are willing to enroll in an 8 week overfeeding study causing a 5-8 % weight gain.
• You are willing to eat all your meals from Pennington and only meals from Pennington for approximately 10 weeks total, even when you are full. Prior to overfeeding 2 Meals per day will be served at Pennington with lunch packed for at least 7 days. After that time participants will receive and eat all (overfeeding) meals at PBRC for 8 weeks. Post-overfeeding will consists of weight-maintenance diet for 1 week. All meals will be monitored at Pennington.
• You are willing to maintain the same level of exercise after enrollment in the study throughout the length of the study.
• You are willing to complete nutritional and activity questionnaires.

Exclusion Criteria:

• You weight > 300 lbs
• You have a history of cardiovascular disease or diabetes.
• You have a fasting blood glucose > 110 mg/dL.
• You have an average screening blood pressure > 140/90.
• You have liver disease.
• You have thyroid disease.
• Have Acid Reflux
• Had cancer in the last 5 years (Some skin cancers OK)
• Have HIV
• Have had an Eating Disorders
• You are pregnant or breastfeeding.
• You have gained or lost more than 3kg in the last 3 months
• You require chronic use of medications including diuretics, steroids and adrenergic-stimulating agents.
• You or a member of your family has a history of blood clots (deep vein thrombosis or pulmonary embolism)
• You have poor circulation, history of bypass operation in your legs, blood coagulation disorders, diagnosed peripheral arterial or vascular disease, cramping pain in your leg muscle during exercise or nerve damage to your legs
• You have varicose veins (per discretion of MD or NP)
• You have had previous GI surgery, obstructive disease of the GI tract, hyper motility disorder or a history of problems of impairment of the gag reflex.
• You have emotional problems such as clinical depression or other diagnosed psychological conditions.
• You are claustrophobic.
• You have metal objects in your body such as implanted rods or surgical clips or magnetic objects that are incompatible with the MRI/MRS.
• You smoke or use tobacco products