Diet and Weight Loss Study - a Weight Loss Trial to Determine Whether Dairy Products Augment Weight Loss for Adults Following an Energy-restricted Weight Loss Study
Trial Snapshot
- Phase
- Phase 4
- Status
- Withdrawn
- Sponsor
- University of Guelph
- Locations
- 1
- Primary Endpoint
- Body fat
Study Overview
Brief Summary
- Objectives Taking a 'whole foods' approach, we will investigate (i) whether consumption of isocaloric diets containing ≥4 vs. ≤1 servings of dairy products per day for 16 weeks results in greater body fat loss in energy-restricted overweight/obese premenopausal women; (ii) the role of dairy product consumption in influencing physiological and metabolic factors which may precede or accompany changes in body composition, including in enzymes which synthesize and break down body fat; and (iii) factors, including obesity phenotype, which may influence the response of body composition to dairy product consumption.
- Background
With the obesity epidemic showing no signs of abating, there is ongoing interest, both at the lay public and scientific levels, in manipulating the diet to promote weight, specifically fat, loss. One such promising manipulation is an increase in, or perhaps more precisely, an isocaloric substitution of, dairy product consumption. The inverse association between Body Mass Index (BMI) and dietary calcium - for which dairy products are the main source - was first described in 1984 and has since been supported by various levels of evidence, but not consistently. Heaney recently described this literature as "confused," which he and Rafferty attribute to important limitations in study design, including lack of low-calcium contrast groups and the fact that body weight/body composition is often a secondary endpoint in studies designed and powered for a different outcome, typically bone health or blood pressure. Confusion has also arisen from the investigation of different interventions (dairy products, dairy calcium, dietary calcium, supplemental calcium), making it difficult to compare and interpret studies. This creates an opportunity for the proposed Dairy and Weight Loss (DAWL) study, with its focus on whole dairy product consumption, to help clear up the confusion surrounding this issue.
**Hypotheses
Overweight/obese, low habitual dairy consuming, premenopausal women randomized to an energy-restricted weight loss diet containing ≥4 servings/day of dairy products (milk, yogurt, cheese) for 16 weeks will lose more body fat than those randomized to an isocaloric diet containing ≤1 servings/day of dairy products.
Detailed Description
"Ground zero" for the DAWL study will be the University of Guelph Body Composition and Metabolism Lab (www.uoguelph.ca/bodycomp), under the direction of the PI.
Sample Size. The investigators plan to complete data collection on a total of 46 women. This sample size is based on an anticipated total body fat mass (FM) loss over 16 weeks of 5.5 kg in the high dairy group and 3.8 kg in the control group. These values are based on data published from 4 studies (5; 20-22). To be conservative in our sample size calculation, we used a higher-than-reported SD of 2.0 kg FM loss. Together, these values indicated that we require 23 women in each group to detect a significant difference in total body FM, with 80% power and 5% alpha. Attrition and non-adherence is anticipated to be approximately 20% to 25%, therefore 30 women in each group will be recruited. We anticipate screening approximately 300+ women to collect 16 weeks of data on a total of 46 eligible and adherent completers, as per Figure 1 below.
Inclusion/Exclusion Criteria. Inclusion criteria include non-smoking, non-pregnant and non-lactating women 18 to 50 years; premenopausal (determined by cessation of menstruation and recent menstrual history to exclude those who are perimenopausal or amennorheic); BMI ≥25.0 kg/m2 (54); usual calcium consumption below the EAR of 800 mg/d (55) to be measured using a validated calcium and vitamin D food frequency questionnaire (FFQ) (56); no sensitivity to dairy; normal liver and kidney function, serum calcium, and complete blood count; 3 mo history of weight stability; and willingness to adhere to study protocol for 16 weeks regardless of treatment, and including no change in physical activity levels. Any vitamin/mineral supplement users will be asked to discontinue supplementation for 4 weeks prior to enrolling in the trial (i.e. "wash out"), as well as for the duration of the trial.
Exclusion criteria include violation of any of the above, or presence of a health condition which might influence weight loss (such as diabetes, CVD, cancer, thyroid disease) or regularly taking medication which may do the same (such as corticosteroids).
Comprehensive Screening/Background Data Collection Visit. Women who pass the initial screen and attend the recruitment session will be invited back to the lab, after having fasted for 12 hours (no food or drink except water), where they will first be asked to sign an informed consent form. Further screening/background data to be collected will include:
Study Design
- Study Type
- Interventional
- Allocation
- Randomized
- Intervention Model
- Parallel
- Primary Purpose
- Treatment
- Masking
- None
Eligibility Criteria
- Ages
- 18 Years to 50 Years (Adult)
- Sex
- Female
- Accepts Healthy Volunteers
- Yes
Inclusion Criteria
- •Otherwise healthy adult premenopausal women with a Body Mass Index (BMI) equal to or greater than 25 kg/m2
- •Age 18 to 50 years
- •Healthy, to be determined from a background health questionnaire and a screening blood panel
- •Willing to comply with study protocol
- •able to visit laboratory regularly throughout the study (therefore must live within reasonable driving distance of the University of Guelph)
Exclusion Criteria
- •Presence of any disease which may interfere with study outcomes including cardiovascular disease, diabetes, cancer, thyroid problem, renal disease, liver disease
- •not be willing to comply with study protocol
Arms & Interventions
Lifestyle counselling
These participants will be assigned to a 500 kcal/day energy-restricted diet that is low in dairy products (no more than 1 serving per day).
Intervention: Low dairy (Other)
High dairy
These participants will be assigned a 500 kcal/day energy-restricted diet that is high in dairy (4 or more servings per day).
Intervention: High dairy (Other)
Outcomes
Primary Outcomes
Body fat
Time Frame: 16 weeks
Whole body fat will be measured at baseline (Week 0) and follow-up (Week 16) by dual energy x-ray absorptiometry
Secondary Outcomes
- Body mass index (BMI)(16 weeks)
- Body weight(16 weeks)
- Waist and hip circumference(16 weeks)
- Fat-free mass(16 weeks)
- Biochemistry(16 weeks)
- Blood pressure(16 weeks)