EAL

PDM: Prediabetes (2013)

Citation:

Lindstrom J, Peltonen M, Eriksson JG, Louheranta A, Fogelholm M, Uusitupa M, Tuomilehto J. High-fibre, low-fat diet predicts long-term weight loss and decreased type 2 diabetes risk: The Finnish Diabetes Prevention Study. Diabetologia, 2006; 49: 912-920.

PubMed ID: 16541277

Study Design:

Randomized Controlled Trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

POSITIVE: See Quality Criteria Checklist below.

Research Purpose:

To investigate the association of dietary macronutrient composition and energy density with the change in body weight and waist circumference and diabetes incidence in the Finnish Diabetes Prevention Study.

Inclusion Criteria:

Individuals in the Finnish Diabetes Prevention Study
Middle-age (40-64 years old)
Overweight (BMI>25kg/m²)
Impaired glucose tolerance according to WHO 1985 criteria.

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment

Participants in Finnish Diabetes Prevention Study, details published elsewhere.

Design

Randomized Controlled Trial

Participants randomized to receive either standard care (control) or intensive dietary and exercise counseling.

Blinding used

Not applicable

Intervention

All study participants were advised to lose weight, increase physical activity and consume a moderate-fat (total fat<30% of energy, saturated fat<10% of energy, high fiber (>15 grams per 1,000kcal)
Intervention group received individualized, detailed dietary counseling with seven sessions during the first year and every three months thereafter. They were also offered free supervised resistance-training-based physical activity sessions. 48 of the participants in the intervention group chose to participate in a two- to five-week very low calorie diet phase to boost weight reduction.
Control group received "standard care".

Statistical Analysis

The two treatment groups were pooled and group assignment was used as a cofactor in the adjusted models
Last-observation-carried-forward method was used in the calculations for those who were diagnosed with diabetes or dropped out before the three-year visit
ANCOVA and x² were used to analyze the baseline and follow-up period differences
The Cox model was used to calculate the hazards ratio for developing diabetes between quartiles of dietary intake; analyses were adjusted for group assignment, sex, age, physical activity, baseline weight, baseline nutrient intake and the weight change from baseline to year three.

Data Collection Summary:

Timing of Measurements

Baseline and annual clinical examinations and questionnaires.

Dependent Variables

Development of Type 2 diabetes
Change in weight.

Independent Variables

Intervention group received intensive individualized dietary counseling and resistance-training based physical activity sessions
Control group received "standard care".

Control Variables

Group assignment
Sex
Age
Physical activity
Baseline weight
Baseline nutrient intake
Weight change from baseline to year three.

Description of Actual Data Sample:

Initial N: 522
- 172 men
- 350 women
Attrition (final N): 500 subjects with follow-up data
Age: 55±7 years old
Ethnicity: Not specified
Other relevant demographics:
Anthropometrics:
Location: Helsinki, Finland.

Summary of Results:

Variables	No Diabetes (N=386)	Diabetes (N=114)	Statistical Significance of Group Difference
Weight
Baseline	85±13	91±15	P<0.001
Year 3	82±13	92±16	P<0.001
BMI
Baseline	30.8±4.4	32.3±4.6	P<0.001
Year 3	29.8±4.5	32.5±4.9	P<0.001
Waist circumference (cm)
Baseline	100±10	105±12	P<0.001
Year 3	97±11	105±12	P<0.001
Fasting plasma glucose (mmol/L)
Baseline	6.0±0.7	6.5±0.9	P<0.001
Year 3	6.0±0.6	7.1±1.0	P<0.001
Carbohydrates (E%)
Baseline	44±7	42±7	P=0.011
Follow-up (mean of years one to three)	47±6	44±6	P=0.002
Fat (E%)
Baseline	36±6	37±7	P=0.13
Follow-up	33±5	35±6	P=0.001
Cholesterol (mg)
Baseline	311±136	306±123	P=0.81
Follow-up	261±99	291±114	P=0.009
Leisure time physical activity (minutes per week)
Baseline	342 (193-551)	289 (124-580)	P=0.20
Follow-up	400 (265-604)	279 (158-469)	P<0.001

Other Findings

Individuals with low fat and high fiber intakes lost more weight compared with those consuming a high fat, low fiber diet (3.1 vs. 0.7kg after three years)
Fiber density, fat E% and energy density of the diet during the follow-up were associated with weight reduction
Weight loss was related to an increase in fiber and decrease in fat and energy density
The most significant dietary predictor for achieving weight reduction was energy density (OR 0.19 (95% CI 0.08-0.41)
High fiber density and lower fat intake were associated with a reduced diabetes risk
Hazard ratios for diabetes incidence during a mean follow-up of 4.1 years were (highest compared with lowest quartile): 0.38 (95% CI: 0.19-0.77) for fiber intake, 2.14 (95% CI: 1.16-3.92) for fat intake, and 1.73 (95% CI: 0.89-3.38) for saturated fat intake, after adjustment for sex, intervention assignment, weight and weight change, physical activity, baseline two-hour plasma glucose and the intake of the nutrient being investigated.
Compared with the low fat, high fiber category, hazard ratios were 1.98 (95% CI: 0.98-4.02), 2.68 (95% CI: 1.40-5.10), and 1.89 (95% CI: 1.09-3.30) for low fat/low fiber, high fat/high fiber, and high fat/low fiber, respectively.
The adjusted three-year weight reduction among those whose diet was both low in fat and high in fiber was 3.1kg (95% CI 2.3-3.9 kg).
Glycemic, lipid, blood pressure and renal outcomes were not reported.

Author Conclusion:

Dietary fat and fiber intake are significant predictors of sustained weight reduction and progression to type 2 diabetes in high-risk subjects.

Funding Source:

Government:	Ministry of Education
University/Hospital:	Finnish Academy, EVO funds from Tampere and Kuopio University Hospitals
Other:	Novo Nordisk Foundation, Yrjo Jahnsson Foundation, Juho Vainio Foundation, Finnish Diabetes Research Foundation

Reviewer Comments:

Mentions in abstract that participants were randomized but that is not discussed in the subjects and methods section (this was part of a larger study, Finnish Diabetes Prevention Study, and states that the study design was described in detail earlier).
Provides numbers of the participants who did not participate in follow-up visits or who had missing data but did not mention if they were in intervention or control group.

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?	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?	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)	???
	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.)	Yes
	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?	N/A
	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%.)	???
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	???
	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?	No
	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?	N/A
	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?	Yes
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	N/A
	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?	Yes
	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)?	Yes
	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