The EAL is seeking RDNs and NDTRs who work with patients, clients, or the public to treat children and adolescents living with type 1 diabetes, for participation in a usability test and focus group. Interested participants should email a professional resume to by July 15, 2024.

MNT: Weight Management (2015)

Chaput J, Tremblay A. Sleeping habits predict the magnitude of fat loss in adults exposed to moderate caloric restriction. Obesity Facts, 2012; 5: 561-566. PubMed ID: 22854682
Study Design:
Retrospective Cohort Study
B - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
  • To verify whether sleeping habits affect the magnitude of fat loss in overweight and obese adults subjected to moderate caloric restriction
  • Hypothesis: Both sleep quantity and quality at baseline predict the success of a weight-reducing program in adults.
Inclusion Criteria:
  • Healthy
  • Overweight and obese
  • Men and women
  • Aged between 25 years and 50 years
  • Absence of menopause for women (cessation of menstruation)
  • Stable body weight (body weight change of less than three kg for two months before intervention)
  • Fewer than three periods of 20 minutes of physical activity per week
  • No use of medication that could affect body weight
  • No smoking
  • Normal BP values (less than 140/90)
  • Consumption of no more than 10 alcoholic beverages per week
  • Consumption of no more than five cups of coffee per day.
Exclusion Criteria:
  • Unhealthy
  • Normal weight
  • Menopause
  • Unstable body weight
  • Three or more periods of 20 minutes of physical activity per week
  • Use of medication that could affect body weight
  • Smoking
  • High BP values
  • Consumption of more than 10 alcoholic beverages per week
  • Consumption of more than five cups of coffee per day.
Description of Study Protocol:


Recruitment methods were not reported.


  • For this study, three previously-published weight loss studies have been pooled together. Only individuals involved in the control groups of these studies were used for statistical analysis in the present study.
  • Participants were subjected to moderate caloric restriction for 15 to 24 weeks, depending on the study
  • Data was collected at baseline and at the end of the study.


  • Participants were subjected to a 600kcal to 700kcal-per-day decrease in energy intake for 15 to 24 weeks, depending on the study
  • Each participant met with the assigned dietitian every two weeks until the completion of the study.

Statistical Analysis

  • Multiple linear regression analysis was used, adjusting for age, sex, baseline BMI, length of intervention and change in energy intake as covariates.
  • A two-tailed P-value of less than 0.05 was considered statistically significant.
Data Collection Summary:

Timing of Measurements

Baseline and at the end of the weight loss program (between 15 weeks and 24 weeks, depending on each of the three programs).

Dependent Variables

  • Sleep quality and sleep duration, measured by the Pittsburgh Sleep Quality Index (PSQI) and assessed only at baseline
  • Body fat mass, measured by dual-energy X-ray absorptiometry
  • Waist cirumference, measured at the line between the lower border of the last rib and the upper border of the ileac crest
  • Dietary intake, measured by a three-day food record (two weekdays and one weekend day) and estimated by a dietitian using a computerized version of the Canadian Nutrient File.

Independent Variables

Energy restriction (600kcal- to 700kcal-per-day decrease in energy intake supervised by a dietitian) diet and time (zero week baseline to 15 to 24 weeks post-test).

Control Variables

Age, sex, BMI, length of intervention and can change in daily energy intake (kJ per day) was used as a covariates.
Description of Actual Data Sample:
  • Initial N: 123 (70 male, 53 female)
  • Attrition (final N): 123
  • Age: 41.1±6.0 years
  • Ethnicity: Not described
  • Other relevant demographics: Not described.


  • Body weight: 94.7±14.5kg
  • BMI: 33.2±3.6kg/m2
  • Waist circumference: 106.4±10.1cm
  • Fat mass: 35.7±8.3kg
  • Fat mass: 38.1±7.1%
  • Sleep duration: 7.1±1.0 hours
  • PSQI (total score): 4.8±2.9
  • Energy intake: 5,242±2,031kJ per day.

Quebec, Canada.

Summary of Results:

Key Findings

  • Mean weight loss of all participants over the dietary intervention was 4.5±3.9kg, 76% of which came from fat stores
  • A significant positive relationship between sleep duration and loss of body fat was observed, both in absolute (adjusted beta, 0.72kg per hour; P<0.05) and relative terms (adjusted beta, 0.77% per hour; P<0.01), after adjusting for covariates
  • Sleep quality was inversely related to both fat mass loss (adjusted beta, -0.19; P<0.05) and percentage body fat loss (adjusted beta, -0.21; P<0.01) after adjusting for covariates, suggesting that a better sleep quality was associated with greater fat mass loss.
Author Conclusion:
  • Both sleep quantity and quality at baseline can predict the magnitude of fat loss in adults exposed to moderate caloric restriction
  • Adequate sleep might influence the success of a weight loss intervention and perhaps sleep should be included as part of the lifestyle package that traditionally has focused on diet and exercise.
Funding Source:
Government: Canadian Institutes of Health Research
Wyeth Consumer Healthcare Inc., Dairy Farmers of Canada
Food Company:
Pharmaceutical/Dietary Supplement Company:
US National Dairy Council
Reviewer Comments:
  • Small sample size
  • Questionnaire-based measurements (sleep duration and diet assessment)
  • Residual confounding (other factors, such as personality traits, education factors or other lifestyle qualities, may affect sleeping habits and adherence to dietary intervention)
  • Study is well suited for the identification of associations and does not permit causal inferences.
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? Yes
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? N/A
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? Yes
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? ???
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? No
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? ???
  6.6. Were extra or unplanned treatments described? ???
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes