Studies in the literature suggest that people with obesity have an excess of stored iron. There is possibly an inverse relationship between ferritin levels and the actions of insulin on glycemic control. The reduction of stored iron by simply donating blood could result in improvements in glycemic control in people with obesity and prediabetes. We propose, to reduce ferritin levels through a standard donation of a unit of whole blood, and to measure if it positively affects glycemic control.

Individuals with pre-diabetes and abdominal obesity will be randomized to either a donation group (DON) or a control group (CONT) in a double-blind fashion (RCT).

Insulin sensitivity during an oral glucose tolerance test (OGTT) and isotopically measured rate of appearance of endogenous and exogenous glucose will be measured on 2 occasions.

1. Two weeks prior to DON/CONT
2. Two weeks after to DON/CONT

Indexes of the bodily iron stores will be measured after DON/CONT to evaluate if the primary treatment was effective.

Inclusion Criteria:

• have not donated in the last 3 months
• IMC>25
• fasting blood glucose 100-125 mg/dL
• glycosylated hemoglobin levels between 5.7-6.4%

Exclusion Criteria:

• to not meet donor bank requirements
• insulin treatment for diabetes
• anemia
• hereditary hemochromatosis
• heart disease
• familial hypertriglyceridemia or hypobetalipoproteinemia
• any disease that requires medication that interferes with iron or glucose metabolism

data will be shared upon reasonable request.

participants in the control group will have the standard blood bank donation venipuncture, but no blood will be withdrawn (sham donation).