The Effect of Dairy Intake on Body Weight and Composition and Metabolic Health in Adolescents and Seniors

The goal of this study is to examine how regular dairy intake affects body weight, body composition, and metabolic health in overweight and obese adolescents (ages 15-18) and older adults (ages 60-80) over six months. We are inviting eligible individuals to participate in this study at the Nutrition Intervention Center, Department of Nutritional Sciences, University of Toronto. Participants will be randomly divided into two groups. The intervention (dairy) group will consume three servings of dairy per day (milk, yogurt, and cheese) before breakfast, lunch, and dinner. The control (low-dairy) group will continue their usual diet, keeping dairy intake to less than one serving per day.

Participants will have biweekly sessions with a registered dietitian to be guided to follow Canada's Food Guide, monitor their dietary intake and ensure compliance with their assigned group. In addition, they will visit the Nutrition Intervention Center at weeks 0, 12, and 24 for anthropometric and body composition assessments (weight, height, waist circumference, blood pressure, lean mass, and fat mass), resting metabolic rate, (gait speed, grip strength, and chair stand test just for older adults) and blood markers (fasting blood glucose, insulin, C-peptide, HbA1c, lipid profiles, and inflammatory markers). Each visit will take approximately 4 hours.

Before each visit, the participants will be asked to fast overnight for 12 hours, maintain their usual diet and sleep patterns, and avoid exercise and alcohol the day before. The participants will be compensated for their time and travel expenses.

Our secondary objective is to compare the effects of dairy and plant-based alternative products on blood sugar and appetite regulation in adolescents and older adults. Participants will be asked to come to the Nutrition Intervention Center on 3 separate occasions: once for an in-person screening lasting approximately 30 min and 2 times for study visits lasting approximately 2.5 hrs each. The entire study will take at least 2 weeks to complete. You will be asked to fast for 12 hrs (overnight) before each study visit. You will also be instructed to maintain the same dietary and sleep patterns and refrain from exercise and alcohol consumption on the days before the study visits. During these study visits, you will be asked to consume either a dairy or a plant-based alternative product as well as a pizza meal. You will periodically fill out questionnaires rating your feelings and perceptions, and provide blood samples through finger pricks and intravenously through your forearm to measure blood sugar, insulin, hormones, and amino acids. You will be compensated for your time and travel expenses.

Study Overview

• Status: Recruiting
• Conditions: Obesity Prevention; Metabolic Health; Dairy Consumption
• Intervention / Treatment: Other: Counselling to follow Canada's Food Guide and 3 daily servings of Dairy (long-term study); Other: Counselling to follow Canada's Food Guide (long-term study); Other: Dairy (short-term study); Other: Plant-based alternative (short-term study)

• Study Type: Interventional
• Enrollment (Estimated): 240
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Corrina Zhou, MSc; Phone Number: 416-946-3802; Email: corrina.zhou@mail.utoronto.ca
• Study Contact Backup: Name: Shekoufeh Salamat, Ph.D.; Phone Number: 647-657-5242; Email: s.salamat@utoronto.ca

Study Locations

• Canada
  • Toronto, Canada, M5S 3H2
    • Not yet recruiting
    • Nutrition Intervention Center
    • Contact: Corrina Zhou, MSc; Phone Number: 416-946-3802; Email: corrina.zhou@mail.utoronto.ca
    • Contact: Shekoufeh Salamat, Ph.D.; Phone Number: 647-657-5242; Email: s.salamat@utoronto.ca
    • Sub-Investigator: Shekoufeh Salamat, Ph.D.
  • Ontario
    • Toronto, Ontario, Canada, M5S 1A8
      • Recruiting
      • Department of Nutritional Sciences
      • Contact: Shekoufeh SS Salamat, Ph.D.; Phone Number: 416-946-3802; Email: s.salamat@utoronto.ca
      • Contact: Corrina CZ Zhou, Master's degree; Phone Number: 416-946-3802; Email: corinna.zhou@email.utoronto.ca

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria (long-term Study):

• Age 15-18 years old (adolescents) or 60-80 years old (seniors)
• BMI z-score >+1SD, <+2SD (adolescents) or BMI 25-34.9 kg/m2 (seniors)
• Waist circumference > 80 cm for women and > 94 cm for men (seniors)
• FBG 5.6-6.9 mmol/L (prediabetes)
• Willing to follow Canada's Food Guide
• Willing to maintain current dietary supplement use throughout the study.
• Willing to abstain from alcohol consumption for 24 hours before all test visits.
• Willing to avoid vigorous physical activity for 24 hours before all test visits.
• Understands the study procedures and is willing to provide informed consent by the parent/guardian and assent by participant to participate in the study and authorization to release relevant protected health information to the study investigator.

Exclusion Criteria:

• Fasting BG ≥ 7 mmol/L
• Blood pressure systolic ≥ 130mmHg or diastolic ≥ 80mmHg (adolescents) or systolic ≥ 140 mmHg or diastolic pressure ≥ 90 mmHg
• Smoking (tobacco and/or cannabis product use in the last 6 months)
• Thyroid problems
• History of CVDs, diabetes, liver or kidney disease, inflammatory bowel disease, celiac disease, short bowel syndrome, any malabsorption syndrome, pancreatitis, gallbladder, or biliary disease.
• Presence of gastrointestinal disorder or surgeries within the past year.
• Use of the prescription or non-prescription drugs, herbal or nutritional supplements known to affect the outcome of the study as per the investigator's judgment (including prebiotics and probiotics).
• Known to be pregnant, lactating, or not postmenopausal for at least a year and/or is taking hormonal treatments
• Unwillingness or inability to comply with the experimental procedures
• Known intolerance, sensitivity, or allergy to dairy, gluten, or any other study treatments.
• Consumption of protein powders/supplements
• Extreme dietary habits (e.g., Atkins diet, very high-protein diets, etc.)
• Weight gain or loss of > 5% in the previous three months.
• Excessive alcohol intake (more than 2 drinks per day or 9 per week)
• Restrained eating, identified by a score of ≥11 on the Eating Habits Questionnaire

Inclusion Criteria (short-term study):

• Age 14-18 years old (adolescents) or 60-75 years old (older adults)
• BMI z-score >+1SD, <+2SD (adolescents) or BMI 25-30 kg/m2 (older adults)
• Willing to maintain habitual diet, physical activity pattern, and body weight throughout the study.
• Willing to maintain current dietary supplement use throughout the study. On study visit days, subject agrees not to take any supplements until dismissal from the Nutrition Intervention Center.
• Willing to abstain from alcohol consumption for 24hrs prior to all study visits.
• Willing to avoid vigorous physical activity for 24hrs prior to all study visits.
• Willing to refrain from cannabis use throughout the entire duration of the study.
• Willing to refrain from protein supplement use (e.g. protein powder) throughout the entire duration of the study.
• Understands the study procedures, provides informed consent to participate in the study, and authorizes release of relevant protected health information to the study investigator.

Exclusion Criteria (short-term study):

• Smoking
• Thyroid problems
• Lactose intolerance and/or allergies, intolerances, or sensitivities to study treatments
• Previous history of cardiovascular disease, diabetes, liver or kidney disease, inflammatory bowel disease, celiac disease, short bowel syndrome, malabsorptive syndrome, pancreatitis, gallbladder or biliary disease
• Presence of gastrointestinal disorder or surgeries within the past year.
• Inability to comply with the experimental procedures and follow our safety guidelines
• Regular breakfast skipping (>3 days a week)
• On a special diet (e.g. ketogenic, Atkins, high protein) or restrained eaters as identified by a score of >20 on the Eating Attitudes Questionnaire
• Difficulties with eating or swallowing
• Fasting blood glucose >5.6mmol/L measured at screening
• Uncontrolled hypertension (systolic blood pressure >120mmHg, diastolic blood pressure >80mmHg) as defined by the average blood pressure measured at screening
• Weight gain or loss of >10lbs in previous three months
• Consuming prescription or non-prescription drug, herbal or nutritional supplements known to affect outcome of the study as per investigator's judgement

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

8

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: High Dairy - Adolescents (long-term study); Participants in the intervention group will follow Canada's Food Guide and consume 3 servings of dairy per day.	Other: Counselling to follow Canada's Food Guide and 3 daily servings of Dairy (long-term study); Participants aged 15-18 and 60-80 years who are randomly assigned to the intervention group will follow Canada's Food Guide and consume 3 servings of dairy (milk, yogurt, cheese) per day for 24 weeks.
Active Comparator: Low Dairy- Adolescents (long-term study); Participants in the control group will adhere to Canada's Food Guide and keep their dairy intake to less than one serving per day.	Other: Counselling to follow Canada's Food Guide (long-term study); Participants will be instructed to follow Canada's Food Guide.
Experimental: High Dairy - Seniors (long-term study); Participants in the intervention group will follow Canada's Food Guide and consume 3 servings of dairy per day.	Other: Counselling to follow Canada's Food Guide and 3 daily servings of Dairy (long-term study); Participants aged 15-18 and 60-80 years who are randomly assigned to the intervention group will follow Canada's Food Guide and consume 3 servings of dairy (milk, yogurt, cheese) per day for 24 weeks.
Active Comparator: Low Dairy- Seniors (long-term study); Participants in the control group will adhere to Canada's Food Guide and keep their dairy intake to less than one serving per day.	Other: Counselling to follow Canada's Food Guide (long-term study); Participants will be instructed to follow Canada's Food Guide.
Experimental: Dairy arm - Adolescents (short-term study); Participants will consume 2 servings of dairy milk or yogurt.	Other: Dairy (short-term study); The dairy products that participants will be required to consume include: 1) Trial 1: 2% cow's milk; 2) Trial 2: dairy yogurt.
Experimental: Plant-based alternative - Adolescents (short-term study); Participants will consume 2 servings of a commercially available soy milk or plant-based yogurt.	Other: Plant-based alternative (short-term study); The plant-based products that participants will be required to consume include: 1) Trial 1: soy beverage; 2) Trial 2: plant-based yogurt;
Experimental: Dairy arm - Seniors (short-term study); Participants will consume 2 servings of dairy milk or yogurt.	Other: Dairy (short-term study); The dairy products that participants will be required to consume include: 1) Trial 1: 2% cow's milk; 2) Trial 2: dairy yogurt.
Experimental: Plant-based alternative - Seniors (short-term study); Participants will consume 2 servings of a commercially available soy milk or plant-based yogurt.	Other: Plant-based alternative (short-term study); The plant-based products that participants will be required to consume include: 1) Trial 1: soy beverage; 2) Trial 2: plant-based yogurt;

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Body Fat Mass (kg)	Body Fat Mass (BFM) is the primary outcome in the long-term study of the senior group. It will be measured using bioelectrical impedance analysis (BIA).	BFM will be measured at weeks 0, 6, 12, 18, and the end of the study (week 24).
Lean body mass (Kg)	Lean body mass (LBM) is the primary outcome in the long-term study of the senior group. It will be measured using bioelectrical impedance analysis (BIA).	LBM will be measured at weeks 0, 6, 12, 18, and the end of the study (week 24).
Body Mass Index (BMI) z-score	BMI z-score, the primary outcome in the long-term study of the adolescent group, is an age- and sex-adjusted measure of BMI in adolescents. It will be calculated using height and weight measurements and interpreted using WHO growth charts and percentiles.	BMI z-score will be measured at the beginning (week 0), midpoint (week 12), and end of the study (week 24).
Blood Glucose (mmol/L) (short-term study)	Blood glucose, the primary outcome in the short-term studies of adolescents and seniors, will be measured via finger-prick using a glucometer at 0, 5, 20, 35, 50, 65, 95, 125, and 145 minutes after treatment consumption.	Over 145 minutes after treatment consumption at each session, for a total of 2 weekly sessions.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Body Mass Index (BMI) (kg/m²)	BMI will be calculated to assess overall adiposity in seniors using weight and height measurements, applying the formula: BMI = weight (kg) / height (m²).	BMI will be measured at the beginning (week 0), midpoint (week 12), and end of the study (week 24).
Fasting blood glucose (FBG) (mmol/L)	FBS will be measured to assess glycemic control in long-term studies of adolescents and seniors. It will be measured using a finger-prick blood sample and a glucometer after a 12-hour overnight fast.	FBS will be measured at the beginning (week 0), midpoint (week 12), and end of the study (week 24).
HbA1c (%)	HbA1c measures average blood glucose levels over the past 2-3 months. It will be measured in plasma obtained through intravenous blood collection after a 12-hour overnight fast in long-term studies of adolescents and seniors.	HbA1c will be measured at the beginning (week 0), midpoint (week 12), and end of the study (week 24).
Insulin (µU/mL)	Insulin levels will be measured in plasma obtained through intravenous blood collection after a 12-hour overnight fast in long-term studies of adolescents and seniors.	Insulin will be measured at the beginning (week 0), midpoint (week 12), and end of the study (week 24).
C-Peptide (pmol/L)	C-peptide levels will be measured in plasma obtained through intravenous blood collection after a 12-hour overnight fast in long-term studies of adolescents and seniors.	C-Peptide will be measured at the beginning (week 0), midpoint (week 12), and end of the study (week 24).
Homeostatic Model Assessment of Insulin Resistance (HOMA-IR)	HOMA-IR will be calculated as (Fasting Insulin [µU/mL] × Fasting Glucose [mmol/L]) / 22.5 to assess insulin resistance in long-term studies of adolescents and seniors.	HOMA-IR will be measured at the beginning (week 0), midpoint (week 12), and end of the study (week 24).
Total cholesterol (TC) (mmol/L)	TC levels will be measured in plasma obtained through intravenous blood collection after a 12-hour overnight fast in long-term studies of adolescents and seniors.	TC will be measured at the beginning (week 0), midpoint (week 12), and end of the study (week 24).
Low-density lipoprotein cholesterol (LDL-C) (mmol/L)	LDL-C levels will be measured in plasma obtained through intravenous blood collection after a 12-hour overnight fast in long-term studies of adolescents and seniors.	LDL-C will be measured at the beginning (week 0), midpoint (week 12), and end of the study (week 24).
High-density lipoprotein cholesterol (HDL-C) (mmol/L)	HDL-C levels will be measured in plasma obtained through intravenous blood collection after a 12-hour overnight fast in long-term studies of adolescents and seniors.	HDL-C will be measured at the beginning (week 0), midpoint (week 12), and end of the study (week 24).
Triglycerides (mmol/L)	Triglyceride levels will be measured in plasma obtained through intravenous blood collection after a 12-hour overnight fast in long-term studies of adolescents and seniors.	Triglycerides will be measured at the beginning (week 0), midpoint (week 12), and end of the study (week 24).
C-Reactive protein (CRP) (mg/L)	CRP, a marker for assessing systemic inflammation, will be measured in plasma obtained through intravenous blood collection after a 12-hour overnight fast in long-term studies of adolescents and seniors.	CRP will be measured at the beginning (week 0), midpoint (week 12), and end of the study (week 24).
Interleukin-6 (IL-6) (pg/mL)	Interleukin-6 levels will be measured in plasma obtained through intravenous blood collection after a 12-hour overnight fast in long-term studies of adolescents and seniors.	Interleukin-6 will be measured at the beginning (week 0), midpoint (week 12), and end of the study (week 24).
Leptin (ng/mL)	Leptin levels will be measured in plasma obtained through intravenous blood collection after a 12-hour overnight fast in long-term studies of adolescents and seniors.	Leptin will be measured at the beginning (week 0), midpoint (week 12), and end of the study (week 24).
Adiponectin (µg/mL)	Adiponectin levels will be measured in plasma obtained through intravenous blood collection after a 12-hour overnight fast in long-term studies of adolescents and seniors.	Adiponectin will be measured at the beginning (week 0), midpoint (week 12), and end of the study (week 24).
Resting Metabolic Rate (RMR) (kcal/day)	RMR will be measured using indirect calorimetry after an overnight fast and at least 30 minutes of rest in a thermoneutral environment.	RMR will be measured at the beginning (week 0) and end of the study (week 24).
Blood pressure (BP) (mmHg)	Blood pressure will be measured in long-term studies of adolescents and seniors, using an automated sphygmomanometer after the participant has been seated and at rest for 10 minutes.	BP will be measured at the beginning (week 0), midpoint (week 12), and end of the study (week 24).
Waist circumference (WC) (cm)	WC will be measured in long-term studies of adolescents and seniors to assess abdominal adiposity using a standardized measuring tape at the midpoint between the lowest rib and the iliac crest while the participant is in a standing position.	WC will be measured at the beginning (week 0), midpoint (week 12), and end of the study (week 24).
Gait speed (m/s)	Gait speed will be assessed in a long-term study of seniors using a standardized 4-meter walk test as an indicator of physical function.	Gait speed will be measured at weeks 0, 6, 12, 18, and 24.
Grip strength (kg)	Grip strength will be assessed in the long-term study of seniors, using a hand dynamometer as a measure of muscle strength.	Grip strength will be measured at weeks 0, 6, 12, 18, and 24.
Chair stand test	The 30-second chair stand test will be used to assess lower-body strength in the long-term study of seniors. The number of completed stands within 30 seconds will be recorded.	The chair stand test will be performed at weeks 0, 6, 12, 18, and 24.
Urinary Urea Nitrogen (UUN)	Urinary urea nitrogen will be measured from a complete 24-hour urine collection in a subset of participants to estimate dietary protein intake and nitrogen balance in this long-term study of seniors.	Urinary urea nitrogen will be measured at baseline (week 0) and at week 24.
Insulin (µU/mL) (short-term study)	Insulin will be measured in the plasma through intravenous blood collection at 0, 35, 65, 125, and 145 minutes after treatment consumption.	Over 145 minutes after treatment consumption at each session, for a total of 2 weekly sessions.
C-peptide (nmol/L) (short-term study)	C-peptide will be measured in the plasma through intravenous blood collection at 0, 35, 65, 125, and 145 minutes after treatment consumption.	Over 145 minutes after treatment consumption at each session, for a total of 2 weekly sessions.
Glucagon-like Peptide-1 (GLP-1) (short-term study)	GLP-1 will be measured in the plasma through intravenous blood collection at 0, 35, 65, 125, and 145 minutes after treatment consumption.	Over 145 minutes after treatment consumption at each session, for a total of 2 weekly sessions.
Amino acids (µmol/L) (short-term study)	Amino acid concentrations will be measured in the plasma through intravenous blood collection at 0, 35, 65, 125, and 145 minutes after treatment consumption.	Over 145 minutes after treatment consumption at each session, for a total of 2 weekly sessions.
Subjective Appetite (short-term study)	Subjective appetite will be assessed through Adaptive Visual Analogue Scales (AVAS) questionnaires completed at 0, 5, 20, 35, 50, 65, 95, 125 and 145 minutes after treatment consumption and through an ad libitum pizza meal provided at 125 minutes post-treatment consumption, where participants will be instructed to eat until they are comfortably full over 20 minutes.	Over 145 minutes after treatment consumption at each session, for a total of 2 weekly sessions.
Food intake (Kcal) (short-term study)	Ad libitum food intake (kcal) will be assessed during a standardized pizza meal provided 2 hours after treatment consumption, consumed over 20 minutes.	Assessed from 125 to 145 minutes following treatment consumption.

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Dietary intake	Dietary intake and adherence to Canada's Food Guide will be assessed using a 3-day food record, the modified Canadian Food Intake Screener (mCFIS), the Canadian Eating Practices Screener (CEPS), and a knowledge, attitude, and practice questionnaire (KAPQ).	Three-day food records will be collected every six weeks; the mCFIS and CEPS will be administered monthly; and the KAPQ will be administered at weeks 0, 12, and 24.

Collaborators and Investigators

• Sponsor: University of Toronto
• Investigators: Principal Investigator: G Harvey Anderson, Ph.D., University of Toronto

Study record dates

Study Major Dates

• Study Start (Estimated): June 1, 2026
• Primary Completion (Estimated): June 1, 2027
• Study Completion (Estimated): June 1, 2028

Study Registration Dates

• First Submitted: March 10, 2025
• First Submitted That Met QC Criteria: March 13, 2025
• First Posted (Actual): March 17, 2025

Study Record Updates

• Last Update Posted (Actual): March 5, 2026
• Last Update Submitted That Met QC Criteria: March 3, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: Adolescents; Obesity; Insulin resistance; HbA1c; Seniors; Type2 Diabetes; BMI z-score; Dairy intake
• Additional Relevant MeSH Terms: Nutrition Disorders; Metabolic Diseases; Overnutrition; Body Weight; Glucose Metabolism Disorders; Hyperinsulinism; Overweight; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Obesity; Insulin Resistance
• Other Study ID Numbers: 48001

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: IPD will not be shared, as all data will be de-identified and pooled during the analysis. Only researchers directly involved in the study will have access to the data.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No