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DLM: Elevated Triglycerides, Carbohydrate and Fat (2007)

Jacobs B, De Angelis-Schierbaum G, Egert S, Assmann G, Kratz M. Individual serum triglyceride responses to high-fat and low-fat diets differ in men with modest and severe hypertriglyceridemia, J. Nutr., 134: 1400-1405, 2004.
Study Design:
Randomized Crossover Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To compare the effects of high-fat and low-fat diets on serum triglyceride concentrations and additionally on serum concentrations of total, LDL-, and HDL-cholesterol as well to determine the effects on LDL susceptibility to oxidation and urinary isoprostanoid excretion as a measure of in vivo oxidative stress. 
Inclusion Criteria:

Males with fasting triglyceride (TG) concentrations >2.3 mmol/L on at least 2 occasions.

BMI 30 kg/m2 or less

Exclusion Criteria:

History of symptoms or markers of type III hyperlipidemia

Apolipoprotein C-11 deficiency, diabetes mellitus, pancreatitis

Liver, kidney or thyroid dysfunction

Coronary heart disease

Use of tobacco, regular consumption of large amounts of alcohol

Description of Study Protocol:


Outpatient lipid clinic of the University of Muenster 



Randomized crossover


Blinding used (if applicable)


Intervention (if applicable)

 High-fat diet versus low-fat diet

Statistical Analysis

Number of study subjects was determined by power analysis to detect a difference in serum TG concentration of at least 0.56 mmol/L (50 mg/dL) between subjects consuming the 2 test diets with a power of 80%.  Statistical analyses were conducted using the Statistical Package for the Social Sciences (version 10; SPSS).  The distribution of means was approximateely normal for most variables, as shown by normal plots and histograms of the data and by Kolmogorov-Smirnov tests. In contrast, serum TG concentrations did not appear to be normally distributed and were logarithmically transformed.  Mean differences and 95% CI values were calculated by two-tailed t tests to assess the effect of diet order;  levels did not differ between these 2 time points.  Effects of the high-fat and low-fat diets and differences between them were assessed by two-tailed paired t tests.  Results were considered significant at values of P < 0.05.


Data Collection Summary:

Timing of Measurements

There were four consecutive dietary periods: a 2 week acclimation period, a 3 week dietary period, a 2 week washout and a second 3 week dietary period.  Three day food records were completed during each period plus a second three day food record completed during each dietary period.  Blood samples were taken at baseline, and before and after each of the diet periods.  Additional venous blood samples were taken on day 7 and 14 of each diet period.  Morning urine samples were collected at each visit.


Dependent Variables

  • Variable 1: Bloods were drawn after an overnight fast of 10 h.  After 30 to 60 minutes, serum and plasma containing EDTA were obtained by centrifugation at 2000 X g for 15 minutes at 100C.  Serum and EDTA plasma samples were immediately frozen at -800C and stored until analysis.  Serum concentrations of total cholesterol and TG were measured using enzymatic assays.  The HDL-cholesterol concentration was measured by a precipitation method and the LDL-concentration was measured after precipitation of LDL with dextran sulfate.   Serum concentations of apo A-1 and apo B were measured using immunoturbidimetric assays.  All of these measuremnets were performed in series within 1 d, using a Hitachi 917 autoanalyzer.  Serum TG and pancreatic enzyme concentrations were measured immediately after each clinic visit to detect critically high TG levels. 
  • Variable 2: LDL was separated from EDTA plama by density gradient centrifugation in a single 2-h session.  After centrifugation, the LDL was collected using a syringe and needle, then filtered through a sterile 0.22- µm filter into sterile vacuum containers and stored in darkness at 40C.  Susceptibility to oxidation was measured on the following day.  All samples from each subject were measured in a single session, yielding intraassay CV values of 2.7, 3.8, and 4.5% for the measurements of lag time, rate of propagation, and maximum amount of conjuated diene formation, respectively.
  • Morning urine samples had 0.002% butylated hydroxytoluene added and were frozen at -800C until analysis.  Levels of 8-iso-prostaglandin Fwere measured with a commercially available competitive enxyme immunoassay.  All samples from each subject were measured on the same plate.  An intraassay CV was 3.0%.  Urinary creatinine was measured by an automated kinetic procedure using a Hitachi 747 autoanalyzer.  All samples were measured within 1 day. 


  • Independent Variables

The high-fat (39.9% energy ± 1.4) and low-fat (28.8% energy ± 1.5) diets were isocaloric (2940 kcal ± 215 vs 2892 ± 239), rich in monounsaturated fatty acids (MUFAs) (17.6 ± 0.7 vs. 12.6 ± 0.7% energy), long-chain (n-3)-polyunsaturated fatty acids (PUFAs) (1.6 ± 0.2 vs. 1.8 ± 0.2% energy), fiber (50 vs. 44 gm), and complex carbohydrates (26.2 ± 1.3 vs. 34.3 ± 2.9 % energy),  and without alcohol.  The diets consisted of conventional mixed foods which the free-living subjects ate throughout the study after receiving detailed dietary insturctions from a trained nutritionist.  The subjects and their wives also received a study booklet with information on amounts and types of food items for meal preparation and snacks.  Refined sugars, sweets, soft drinks and alcoholic drinks were not permitted.  The subjects were permitted 100 kcal each day as free-choice foods from an approved list.  The daily amounts of food were calculated for levels of energy intake ranging from 1800 to 3200 kcal/d.  To standardized the intake of long-chain (n-3)-PUFAs, the subjects were provided with canned herring and mackerel and were requested to consume 1 can/d of either during both dietary periods.  Rapeseed oil, margarine, nuts, cereals, and snacks were also supplied.  Compliance was assessed by 3-d food records as described above.  A nutritionist was in regular contact with the sujbects at clinic visits and by phone to provide support and motivations.  The subjects also recorded their daily free-choice items and any deviations from the diets in the study booklet.  The diets were calculated on the basis of standard German food tables.

Control Variables


Description of Actual Data Sample:


Initial N:  17 males

Attrition (final N): 14 (1 withdrew because of conflicts with work demands and 2 withdrew becasue they were unwilling or unable to comply with the dietary regimen)

Age: 32 to 57 y (mean ± SD = 43.8 ± 7.0 y)

Ethnicity: not described

Other relevant demographics

Anthropometrics: baseline levels of TG, cholesterol (total, LDL, HDL) and BMI were similar.  Two subjects had a baseline TG too high to meaure HDL and apo B. 

Location: Muenster, Germany


Summary of Results:



High Fat Diet


Measures and confidence intervals

High Fat Diet


Stat Signif of Group Difference

Low Fat Diet


Measures and confidence intervals

Low Fat Diet


Stat Signif of Group Difference

Stat Signif of High-fat vs. Low-Fat





2.33±1.49  <0.001


2.46±0.88  0.048


Total cholesterol,



5.40±1.34 0.006 


 5.39±1.27 0.004




3.06±1.02 0.568


3.02±0.85 0.163


HDL-cholesterol 0.98±0.28  1.01±0.28 0.439  1.01±0.27  1.01±0.37  1.000 0.970
Apo-A-1, mg/L 1306±220 1261± 221  0.009 1329±254 1272±317 0.066 0.819
Apo B, mg/L 1146±297 1109±307 0.326 1207±317 1091±253 0.088 0.746

Body Weight, kg

83.0±8.0 82.9±7.9 0.604 83.0±8.1 83.1±8.3 0.752 0.559


Other Findings

Subjects were split into 2 subgroups in response to the diet.  Two subjects had similar serum TG levels at the end of each diet period while 7 had lower mean TG levels at the end of the high-fat diet (1.41 vs. 2.66 mmol/L for the high-fat and low-fat diet periods, respectively).   Five subjects had lower mean TG levels at the end of the low-fat diet period (1.89 vs. 3.32 mmol/L for the low-fat and high-fat diet periods, respectively).  Subjects whose serum TG concentrations were lower at the end of the low-fat diet period had higher initial mean TG concentrations than subjects whose TG concentrations were lower at the end of the high-fat diet period (9.56 and 5.19 mmol/L, respectively; p=0.046).

Urine concentations of PGF did not differ among the different study periods. 

The low-fat diet lowered the susceptibility of plasma LDL to oxidation in subjects compared to the high-fat diet.  The rate of propagation mean difference = -2.07 nmol conjugated dienes/(min . mol LDL-cholesterol), 95% CI = -.98 to -3.34 nmol conjugated dienes/(min . mol LDL-cholesterol).  The lower maximal formation of conjugated dienes mean difference = -106 nmol conjugated dienes/mol LDL-cholesterol, 95% CI = -21 to -191 nmol conjugated dienes/mol LDL-cholesterol.  The lag time until the start of oxidation tended to be longer (p=0.06) after consumption of the low-fat diet (mean difference = +2.3 min, 95% CI = -0.11 to +4.69 min).


Author Conclusion:

A diet rich in unsaturated fatty acids [particularly long-chain (n-3)-PUFAs], fiber, and complex carbohydrates and low in saturated fatty acids, simple carbohydrates, and alcohol can be used effectively to treat hypertriglyceridemias.  Individuals with serum TG concentrations <4.5 mmol/L benefit more from such a diet if its fat content is relatively high.  A considerable number of individuals with serum TG concentration >4.5 mmol/L achieve lower serum TG levels by consuming a low-fat diet. 

Funding Source:
University/Hospital: Univesity of Miami School of Medicine, Miami VA Medical Center
Reviewer Comments:
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) 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.) 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%.) 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? 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? 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)? N/A
  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? ???