Tree Nut Consumption to Reduce Abdominal Adiposity

A major contributing factor to the rising waist circumference of U.S. young adults is the increase in snacking behavior. Both the frequency of snacking during the day and the percentage of adults who engage in snacking has risen; national data indicates snacking comprises 15-25% of the total daily caloric intake of young and middle-aged adults. Unfortunately, current typical snack items are energy rich, providing high intake of carbohydrates and sugars, as opposed to nuts that are nutrient rich. In prior work with middle-aged adults, the investigators found that consuming tree nuts daily as between-meal snacks for a period of 16 weeks significantly reduced intra-abdominal (visceral) fat and waist circumference, which was associated with altered plasma fatty acid profiles and higher fatty acid oxidation rates. Based on prior findings, the investigators propose to determine whether consuming mixed tree nuts as replacement for typical high carbohydrate snacks reduces abdominal obesity and waist circumference in millennials at risk for MetS. The overarching hypothesis, based on significant preliminary data, is that the quantity and metabolic function of abdominal fat is a key intermediary factor by which greater tree nut consumption reduces ectopic lipid storage (including the accumulation of intra-abdominal [visceral] fat), improves fatty acid and lipoprotein metabolism, reduces systemic inflammation and insulin resistance, and thus, reduces risk for MetS in millennial-generation age individuals. The hypothesis will be tested by determining: 1) the effect of consuming mixed tree nuts as daily snacks for 16 weeks on waist circumference and the quantity of abdominal fat (subcutaneous and visceral fat); 2) the effect of consuming mixed tree nuts as daily snacks for 16 weeks on circulating fatty acid profiles, glucose tolerance and insulin resistance, circulating lipids and lipoproteins, and circulating markers of inflammation; and 3) the effect of consuming mixed tree nuts as daily snacks for 16 weeks on abdominal tissue expression of genes that regulate inflammation, insulin resistance, and cardiometabolic mediators of MetS risk.

Inclusion criteria

• Age 22-36 years
• BMI 18.5 to 34.9
• At least one risk factor for metabolic syndrome based on waist circumference, HDL level or triglyceride level

Exclusion criteria

• Tree nut allergy
• Diagnosed chronic disease
• Medication for dyslipidemia or hypertension
• Smoke
• Weight loss medication
• Narcotic medication or illicit drug use
• Pregnancy or lactation or postmenopausal