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Completed

NCT Number: NCT05736432

Impacts of Wild Blueberries on Appetite and Weight Regulation

The objective is to complete a two-phase study to assess how wild blueberries impact regulation of appetite of overweight and obese men and women as well as to determine if wild blueberries can promote more effective weight loss than an isocaloric control. For phase I, the acute effects of consuming 1-cup of frozen wild blueberries mixed into ¾ C of low-fat yogurt will be compared to consuming an isocaloric serving of yogurt mixed with an artificially flavored and colored blueberry syrup. During acute testing, subjective ratings of appetite, glucose metabolism, and appetite-regulating hormones will be assessed. Phase II will consist of an 8-week feeding trial in which the same subjects will consume daily servings of yogurt mixed with either frozen wild blueberries or placebo syrup along with intensive counseling for weight loss. The hypothesis is that wild blueberries will reduce hunger by regulating appetite hormones and promoting beneficial glycemic and insulinemic responses and that daily consumption of wild blueberries will translate to improved adherence to a weight loss regimen and therefore greater weight and fat loss. Secondary aims for Phase II of this project will include exploring the impacts of blueberry consumption during weight loss on antioxidant status, inflammatory markers, blood lipid profiles, glucose status, dietary intake, physical activity and blood pressure.

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Key information

Conditions

Obesity Body Weight Body Weight Changes Nutrition Disorders Nutritional and Metabolic Diseases Overnutrition Overweight Pathological Conditions, Signs and Symptoms Signs and Symptoms Weight Loss

Age range

18 year–50 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Mark Kern, PhD, RD

San Diego, California, 92182-7251, United States

About this study

For Phase I, all subjects will complete two acute feeding trials in random order. One feeding will consist of 1 C frozen wild blueberries along with ¾ C low-fat Mountain High yogurt (total energy intake=170 kcal). The other feeding will consist of an isocaloric feeding of ¾ C yogurt mixed with artificially flavored and colored blueberry syrup (Torani). A standardized meal will be consumed the evening prior to testing to minimize fluctuations during the testing days. Arterialized fingerprick blood samples from heated hands will be collected into Greiner Bio-One MiniCollect™ Capillary Blood Collection System Tubes containing Ethylenediaminetetraacetic acid while fasted and 30, 60 and 120 minutes after food intake for analysis of glucose, insulin, ghrelin, and pancreatic peptide. Appetitive responses (hunger, fullness, desire to eat, and prospective food consumption) will be assessed by 100-mm visual analog scales at baseline and 15, 30, 45, 60, 90, and 120 minutes after intake.

For Phase II, subjects will be equally divided and matched for body fatness into two randomly assigned groups. Both groups will be counseled for weight loss, which will be achieved through a comprehensive program including a) dietary intervention, b) daily text messaging, and c) daily at-home weighing with a WiFi-enabled scale. In addition, groups will be randomly assigned to daily consume the same 170 kcal yogurt parfait described above containing either wild blueberries or placebo as an afternoon snack for 8 weeks. The rationale for the inclusion of a healthy, wild blueberry in yogurt afternoon snack intervention is supported by the National Health And Nutrition Examination Survey analyses that revealed a shift in eating patterns towards the evening in combination with an increase in snacking occasions, particularly in the afternoon/evening hours. Further, the majority of the snacking occasions include unhealthy, high fat/high sugar foods, potentially contributing to unwanted weight gain and obesity. Moreover, since blueberries can elevate pancreatic peptide for at least 2 hours after consumption, this could enhance the likelihood of maintaining lower intake during the evening meal. Thus, overall, it is proposed that the afternoon wild blueberry/yogurt snack will promote satiety and reduce overeating (especially of unhealthy foods) later in the day.

All participants will be counseled to achieve a 500-kcal/d energy deficit (from their baseline eucaloric diet). Energy requirements will be estimated by calculating resting metabolic rate using the equations of Schofield and multiplying by an activity factor of 1.3. The participants will meet with investigators every two-weeks for intensive counseling to ensure adherence to the dietary prescription. Before and after the trial, fasted blood will be collected into tubes for both plasma and serum to assess total antioxidant capacity, C-reactive protein, blood lipid concentrations, glucose and insulin. During lab visits investigators will assess anthropometrics (height, body weight, and body composition via dual x-ray absorptiometry, dietary intake, physical activity behaviors, food cravings, and blood pressure. Adequate samples of blood will be collected to allow us to bank plasma for future analyses if additional funding is obtained in the future.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Overweight or Obese (BMI 25-40)

Exclusion criteria

  • Pregnancy
  • Smoking
  • >5 kg wt fluctuation in the past 3 months
  • exercising > 2 times per week
  • Medical conditions or medications that may affect body weight, metabolism, other outcome measures
  • Allergy to blueberries or yogurt
  • Already eating blueberries more than twice weekly
  • Consumption of >50 g/d alcohol

Treatment and study plan

Blueberries

Dietary Supplement

Experimental condition

Placebo

Dietary Supplement

Placebo condition

Primary outcomes

  1. Plasma Glucose

    Time frame: 8 weeks

    fasted

  2. Total Cholesterol

    Time frame: 8 weeks

    Total Cholesterol

  3. Triglycerides

    Time frame: 8 weeks

    Triglycerides

  4. HDL-Cholesterol

    Time frame: 8 weeks

    HDL-Cholesterol

  5. Insulin

    Time frame: 8 weeks

    Insulin

  6. Ghrelin

    Time frame: 8 weeks

    Ghrelin

  7. Pancreatic peptide

    Time frame: 8 weeks

    Pancreatic peptide

  8. C-Reactive Protein

    Time frame: 8 weeks

    C-Reactive Protein

  9. Total Antioxidant Capacity

    Time frame: 8 weeks

    Colorimetric assay kit using blood serum

  10. Blood Pressure

    Time frame: 8 weeks

    Systolic and Diastolic

  11. Body Composition

    Time frame: 8 weeks

    Daily via bioimpedance Wifi Scales

  12. Body Composition

    Time frame: 8 weeks

    dual x-ray absorptiometry

Sponsors and collaborators

Lead sponsor

San Diego State University

Other

Registry information

Important dates

Study start
2023
Primary completion
2024
Study completion
2025
First posted
Feb 21, 2023
Registry last updated
Feb 21, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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