EAL

FNOA: Assessment of Overweight/Obesity (2012)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

This research examined intentional and unintentional weight loss related to the reasons for intentions for weight loss
All-cause mortality and mortality due to cardiovascular disease (CVD) and non-CVD causes were examined in men aged 56 to 75 years of age.

Inclusion Criteria:

Participants in the British Regional Heart Study who completed the follow-up and study questionnaire 1996 and a subsequent follow-up after seven years.

Exclusion Criteria:

Non-surviving member of the British Regional Heart Study
Missing or incomplete data on participants perceived weight change.

Description of Study Protocol:

Recruitment

Participants in the British Regional Heart Study were recruited from the age-sex registers of one group general practice in 24 towns in England, Wales and Scotland.

Design

Prospective cohort study

In 1978-1980, research nurses administered a questionnaire including questions on smoking, alcohol intake, physical activity and medical history. Height and weight were measured: Body Mass Index (BMI) was calculated.
In 1992 (12 to 14 years later), the same questionnaire was sent to all survivors. Weight change intentions were obtained.
- BMI: Calculated based on reported weight
- Perceived weight change: During previous four years (increased, decreased, not changed, do not know); was it intentional (personal choice, ill health, physician's advice); divided into four categories: Stable, gained, unintentional weight loss, intentional weight loss
- Cardiovascular risk factors: Smoker, occupation/social class, total physical activity score, estimated weekly alcohol intake
- Indicators of ill health: Whether a physician had ever told them they had certain medical condition
- Follow-up: All-cause mortality, CVD morbidity, type 2 diabetes mellitus
Follow-up took place after seven years.

Blinding Used

Implied with measurements.

Statistical Analysis

Cox proportional hazards model to assess relative risk for each weight change category, compared to Stable Group
Adjustments were made for confounding factors: Smoking, social class, BMI, physical activity, alcohol intake and perceived health status were fitted as categorical variables
Obesity and presence of disease were dichotomous variables.

Data Collection Summary:

Timing of Measurements

Subjects from the study completed another questionnaire in 1996 about intentional and unintentional weight loss over the preceding four years and were followed for a subsequent seven years.

Dependent Variables

All cause mortality
CVD morbidity
Development of type 2 diabetes.

Independent Variables

Intentional and unintentional weight loss.

Control Variables

Smoking
Social class
BMI
Physical activity
Alcohol intake
Perceived health status
Obesity
Presence of disease.

Description of Actual Data Sample:

Initial N

7,735 (all male) in 1978 to 1980
5,265 in 1996
4,869 with data on perceived weight change minus those who said their weight fluctuated.

Attrition (Final N)

4,786 (all male).

Age

56 to 75 years.

Ethnicity

Not noted.

Anthropometrics

BMI was higher overall in the "Intentional Weight Loss" Group.

Location

England, Wales and Scotland.

Summary of Results:

Key Findings

Perceived weight change and mortality

Unintentional, but not intentional, weight loss was associated with a higher incidence of all-cause mortality, after adjustments, for both CVD and non-CVD causes
In the Intentional Weight Loss Group, the sub-group of participants who lost weight as a result of personal choice had a significantly lower risk of mortality, compared to the Stable (no change) Group (P=0.05), mainly from non-CVD causes
When the No-Weight Change Group was further divided into those who reported excellent health and those who reported poor or fair health, the latter group showed significantly higher all-cause mortality (RR=1.6; 95% CI, 1.22 to 2.51).

Cause-specific mortality

For all non-CVD deaths:
- 64% cancer
- 19% respiratory
- 17% other non-CVD causes.
Although a small sample size, participants with intentional weight loss from personal choice showed lower mortality risk for cancer and non-cancer causes, compared to those who perceived no weight change.

BMI in 1992, intentionality of weight loss and mortality

Divided into two groups: BMI under 28 and BMI of at least 28 (more than 28 had shown significantly-increased all-cause mortality)
The benefit of intentional weight loss as a personal choice was most prevalent in heavy men (at least 28), with a relative risk of 0.23 (CI, 0.06 to 0.95).

Age, intentionality of weight loss and mortality

Unintentional weight loss was associated with increased risk of mortality in both those under 65 years and at least 65 years of age.

Author Conclusion:

Intentional weight loss of personal choice is associated with lower all-cause mortality and specifically non-CVD mortality in overweight men, compared to no weight change
The older age of men in this study suggests that the earlier in life that the weight loss occurs, the greater the benefit.

Funding Source:

Government:

Department of Health, London, England

Not-for-profit

British Heart Foundation Research Group

Other non-profit:

Reviewer Comments:

Study includes only men, limiting its generalizability to female populations.

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)	N/A
	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)	N/A

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?	Yes
	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?	???
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)	Yes
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	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?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	Yes
	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%.)	Yes
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	Yes
	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?		Yes
	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?	Yes
	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?	N/A
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	Yes
	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