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

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