metabolic and bio-behavioral effects of following recommendations in the dietary guidelines for americans

Conditions: Obesity; Body Weight

Summary: this study, at the western human nutrition research center (whnrc), will focus on whether or not achieving and maintaining a healthy body weight is the most important health promoting recommendation of the dietary guidelines for americans (dga).the investigators hypothesize that improvement in cardiometabolic risk factors resulting from eating a dga style diet will be greater in people whose energy intake is restricted to result in weight loss compared to those who maintain their weight. the investigators further propose that during a state of energy restriction, a higher nutrient quality diet such as the dga style diet pattern, will result in greater improvement in cardiometabolic risk factors compared to a typical american diet (tad) pattern that tends to be lower nutrient quality (more energy-dense and less nutrient-rich.)

this will be a 28-week study including pre-diet testing (week 1), an 8-week controlled feeding period, post-diet testing (week 10), a follow-up period of dietary education and observation, and end of study testing (week 28). during the 8 week feeding, participants will be randomly assigned one of the following diets: 1. dga mediterranean diet pattern at sufficient energy level to maintain body weight (energy balance) 2. dga mediterranean diet pattern at a moderately reduced energy level (negative energy balance) 3. tad diet pattern at a moderately reduced energy level (negative energy balance) in the follow-up phase, the investigators will evaluate how multiple factors may influence body weight management, including previous dietary exposure, as well as the role of cognitive function, executive function, genetics, habitual diet, physical activity, eating behavior, stress and stress responsivity, metabolic flexibility and gut microbiome.

Eligibility criteria:
inclusion criteria: * body mass index (bmi) 23-39.9 kg/m2 or 32-50% body fat percentage * willingness to have blood drawn * the criteria listed above and at least one of the following: fasting glucose ≥100 mg/dl but \<126 mg/dl or fasting triglyceride ≥125 mg/dl or hdl-cholesterol ≤50 mg/dl or blood pressure (bp): systolic bp ≥130 mmhg or diastolic bp ≥85 mmhg or hemoglobin a1c ≥ 5.7 and \<6.5% exclusion criteria: * active participation in another research study * tested positive for covid-19 within the past 10 days * been in close contact with a covid-19 positive person within the past 14 days * blood pressure (bp): systolic bp ≥140 mmhg or diastolic bp ≥90 mmhg * ldl cholesterol ≥190 mg/dl * triglycerides ≥500 mg/dl * current use of smoking or chewing tobacco, e-cigarettes, cigars, vaping, cannabis or other use of nicotine containing products (within the past 6 months) * current use of dietary supplements and/or unwillingness to cease intake of dietary supplements * vegan or vegetarian lifestyle or any other dietary restrictions that would interfere with consuming the intervention foods and beverages (including dietary intolerances, allergies and sensitivities) * unwillingness to consume intervention foods and beverages * engage in more than moderate drinking (\> 1 drink serving per day) or binge drinking (4 drinks within two hours). * unwillingness to cease alcohol intake as required for specific duration of the study * excessive intake of caffeine containing products (excessive defined as ≥ 400 mg/day) * unwillingness to refrain from caffeine intake on lab visit days. * intentional weight change of ≥5% of body weight within 6 months of entry into the study * diagnosis of disordered eating or eating disorder * recent diagnosis of any of the following or measurement on screening lab tests: anemia (hemoglobin \ 200% of upper limit (alt upper limit is 43 u/l or aspartate transaminase (ast) upper limit is 54 u/l) and thyroid function tests: thyroxine (t4, free) \ 1.64 ng/dl; thyroid-stimulating hormone (tsh) \ 5.6 μiu/ml). * history of any of the following: gastric bypass surgery, inflammatory bowel disease (ibd) or other gi conditions that would interfere with consuming the intervention foods, active cancer in the past three years excluding squamous or basal cell carcinomas of the skin that have been handled medically by local excision and other serious medical conditions * recent dental work or have conditions of the oral cavity that would interfere with consuming the intervention foods and beverages * taking any medication in the class of antipsychotics * long term use of antibiotics * taking any over the counter or prescribed medication for any of the following: elevated lipids, elevated glucose, high blood pressure, weight loss or conditions that require corticosteroids (e.g. asthma, arthritis or eczema). * are pregnant, planning to become pregnant within the duration of the study or breastfeeding.

Keywords: dietary guidelines for americans physical activity for americans mediterranean diet controlled feeding women prediabetes metabolic syndrome cognitive function stress, physiological executive function cardiovascular diseases cardiovascular risk factor eating behavior glucose intolerance metabolomic profiling metabolic flexibility gut microbiome genome testing prehypertension insulin resistance insulin sensitivity hypertriglyceridemic waist to hip ratio allostatic load physiology