A Grapefruit Feeding Trial in Healthy, Overweight Adults

Folklore has suggested that consuming grapefruit may promote weight control. Sparse data exist to support this hypothesis, though there is some evidence of health promotional effects regarding blood pressure and lipid profiles. The aims of this randomized controlled trial are to determine the role of grapefruit in: Reducing weight Reducing blood pressure Reducing inflammation Improving the lipid profile. The investigators hypothesize that six weeks of daily consumption of grapefruit will reduce weight, blood pressure, and inflammation while improving the lipid profile in overweight, healthy adults.

Participants followed a diet low in bioactive rich fruits and vegetables and avoided citrus for six weeks

Participants consumed 1/2 grapefruit before each meal (1.5 grapefruit per day) for six weeks. Weight was measured before and after grapefruit consumption to assess weight change. Weight change was considered statistically significant at p<0.05.

Previous studies in animals and humans consuming citrus have resulted in reductions in blood pressure, though no direct effect of grapefruit has ever been demonstrated. Blood pressure was measured at baseline and after the 6 week intervention period (consuming either the control diet or supplementing the diet with 1/2 grapefruit before each meal).

Previous studies in humans and animal models consuming grapefruit or grapefruit bioactives have shown reductions in triglycerides, LDL, and total cholesterol and increases in circulating HDL. These parameters were measured via a common point-of-care system, LDX Cholestech. Lipids were measured at baseline and after the 6 week intervention period (consuming either the control diet or supplementing the diet with 1/2 grapefruit before each meal).

Markers of chronic inflammation, which are also associated with endothelial dysfunction and heart disease, like tumor necrosis factor alpha (TNFalpha), interleukin-1beta (IL-1beta), and soluble vascular cellular adhesion molecule-1 (sV-CAM1) were measured. Inflammatory markers were measured at baseline and after the 6 week intervention period (consuming either the control diet or supplementing the diet with 1/2 grapefruit before each meal).

Inclusion Criteria: Adults, men and premenopausal women BMI: 25-45 kg/m2 Willing to maintain current exercise regimen (not to exceed 10 hours/week) Willing to follow a diet low in bioactive rich fruits and vegetables and with no citrus Exclusion Criteria: History of chronic disease Metabolic disease Inflammatory disease High cholesterol (>225 mg/dL) Smoker Taking medications metabolized by the Cytochrome P450 3A enzyme History of alcohol or drug abuse