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NC: Diabetes Management (2007)


Schafer S, Kantartzis K, Machann J, Venter C, Niess A, Schick F, Machicao F, Haring HU, Fritsche A, Stefan N. Lifestyle intervention in individuals with normal vs. impaired glucose tolerance. Eur J Clin Invest. 2007 Jul; 37 (7): 535-543.

PubMed ID: 17576204
Study Design:
Non-Randomized Controlled Trial
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
  • To determine whether a lifestyle intervention with a fat-reduced diet and an increase in the proportion of unsaturated fats and rich in fiber, together with a moderate increase in physical activity, is similarly effective in Caucasians with normal glucose tolerance (NGT) and impaired glucose tolerance (IGT) to improve glucose tolerance.
  • A secondary research purpose was to determine which fat compartments, ectopic vs. visceral, are most affected by the lifestyle intervention as stated above.
Inclusion Criteria:

Participants were included if they fulfilled at least one of the following criteria:

  • Family history of Type 2 diabetes
  • Body mass index (BMI) greater than 27kg per m2 
  • Diagnosis of IGT
  • Previous diagnosis of gestational diabetes.
Exclusion Criteria:

None stated.

Description of Study Protocol:


Individuals from the southern part of Germany that participated in the Tuebingen Lifestyle Intervention Program ( TULIP)


  • These individuals are participating in a 24-month diet and exercise program designed to prevent Type 2 diabetes (TULIP) 
  • Data included in this study are baseline and nine-month data.

Blinding Used



  • Individuals underwent dietary counseling at baseline and had up to 10 sessions with a dietitian
  • During each visit, participants presented a three-day food diary and discussed the results with the dietitians. Counseling was aimed at:
    • Reducing body weight by at least 5% compared to baseline
    • Reducing intake of calories from fat to less than 30% of energy and saturated fat to no more than 10% 
    • Increasing intake of fiber to at least 15g per 1,000kcal
    • Perform at least three hours of moderate sports per week
  • Dietary intervention was adapted from the diet intervention used in the Finish Diabetes Prevention Study.

 Statistical Analysis

  • Matched pairs T-test
  • Multivariate linear regression analysis.


Data Collection Summary:

Timing of Measurements

Baseline and nine months.

 Dependent Variables

  • Weight: Scale
  • BMI: Calculated as weight divided by the square of height
  • 75g OGTT: Venous samples at zero, 30, 60, 90 and 120 minutes
  • Insulin sensitivity: Calculated from glucose and insulin values during OGTT as proposed by Matsuda and DeFronzo
  • Blood glucose: Bedside glucose analyzer
  • Serum total cholesterol, HDL, LDL: Measured by standard colorimetric method
  • Diet composition: Validated computer program using two representative days of a three-day diary
  • Visceral fat: Measured by magnetic resonance tomography 
  • Liver fat: Measured by proton magnetic resonance spectroscopy (H-MRS)
  • Intramyocellular fat: Measured by proton magnetic resonance spectroscopy (H-MRS)
  • HPA: Standardized self-administered and validated questionnaire to measure physical activity and a habitual physical activity (HPA) score.

Independent Variables

  •       Dietary intervention based on calorie restriction
  •       Physical activity intervention based on three hours weekly. 

Control Variables



Description of Actual Data Sample:
  • Initial N: 181
    • NGT: 54 males, 79 females
    • IGT: 20 males, 28 females
  • Attrition (final N): 143
  • Mean age: 44 NGT; 50 IGT
  • Ethnicity: German population
  • Other relevant demographics: Southern Germany
  • Anthropometrics: IGT vs. NGT 
    • IGT group were an average of six years older and had had higher subcutaneous abdominal fat, compared to NGT group
    • IGT group had higher amounts of visceral fat, liver fat and intramyocellular, compared to NGT group
  • Location: University of Tubingen in Tubingen, Germany.


Summary of Results:



NGT Group

Measures and Confidence Intervals

IGT Group

Measures and Confidence Intervals

Statistical Significance of Group Difference

Weight  (kg)

Decrease of 2.75kg

Decrease of 2.78kg



Decrease of 0.92

Decrease of 1


Fasting Glucose

Decrease of 0.1mm

Decrease of 0.05


Insulin Sensitivity Increase of 2.45 Increase in 0.86 No
OGTT (two-hour) Increase of 0.14mm Decrease of 0.74mm No
LDL Decrease in 4mg/dl Decrease in 6mg/dl No
Triglyceride Decrease in 4mg/dl Decrease in 9mg/dl No

  • Individuals with IGT had a significant decrease in body weight, BMI, fasting insulinaemia, two-hour glycaemia and insulinaemia, LDL-C, triglycerides and TNF-alpha, while insulin sensitivity and adoponectin levels increased
  • Individuals with NGT had a significant decrease in body weight, BMI, fasting glycaemia and insulinaemia, two-hour insulinaemia, total cholesterol, hsCRP and TNF-alpha, while insulin sensitivity and adiponectin levels increased 
  • Insulin secretion remained unchanged in both groups
  • Total body fat, subcutaneous abdominal fat and visceral fat decreased significantly, both in individuals with IGT and NGT
  • Regarding ectopic fat deposition, individuals with IGT had a decrease in liver fat and intramyocellular fat, while only liver fat decreased significantly in individuals with NGT.

Other Findings

  • Visceral fat, liver fat and intramyocellular fat decreased in participants with IGT
  • Changes in visceral fat (-16%) and liver fat (-35%) were significant in participants with NGT
  • The diagnosis of IGT was reversed in 24 out of 48 individuals (50%)
  • 14 of the 133 participants (10.5%) with NGT developed IGT
  • 45% of participants with NGT reached dietary goal of less than 30% fat in total calories
  • 57% of participants with IGT reached dietary goal of less than 30% fat in total calories
  • 41% of participants with NGT increased fiber intake above 15g per 1,000kcal
  • 34% of participants with IGT increased fiber intake above 15g per 1,000kcal
  • 31% of participants with NGT reached dietary goal of weight reduction greater than 5%
  • 29% of participants with IGT reached dietary goal of weight reduction greater than 5%. 
Author Conclusion:
  • After nine months of a lifestyle intervention, half of the participants reached their goals to decrease fat intake and to perform at least three hours of sports per week. The moderate weight loss (5%) and increase of physical activity, resulted in a reduction in total, visceral and ectopic fat, and an increase in insulin sensitivity, which improved glucose tolerance in individuals with IGT, but not with NGT.
  • The beneficial effects of a lifestyle diet and exercise intervention on fat distribution and insulin sensitivity, may also possibly prevent future deterioration in glucose tolerance in participants with NGT
  • The authors also showed that the NGT participants followed the intervention instructions just as well as the participants with IGT. Whether this will continue through 24 months and beyond is yet to be determined.
  • Limitations were stated such as small sample size and the inability to determine whether the lifestyle intervention in the individuals with NGT would prevent Type 2 diabetes.
Funding Source:
Government: Deutsche Forschungsgemeinschaft (Germany)
Reviewer Comments:
  • The authors did show that a moderate (5%) weight loss under a lifestyle intervention of diet and physical activity, did help to increase insulin sensitivity in individuals with IGT. Reduction in total, visceral and ectopic fat were also shown in both the IGT and NGT groups.
  • Concerning the nutrition intervention, the study mentioned certain dietary parameters in the nutrition counseling sessions discussed, but it was not explicit with how the education was done (i.e., cognitive behavior therapy vs. standard dissemination of nutrition education)
  • With the activity portion of the lifestyle intervention, I was unsure what was defined as "sports"
  • I was disappointed with the lack of statistical significance with many of the dependent variables measured in the study after nine months of intervention.
Quality Criteria Checklist: Review Articles
Relevance Questions
  1. Will the answer if true, have a direct bearing on the health of patients? Yes
  2. Is the outcome or topic something that patients/clients/population groups would care about? Yes
  3. Is the problem addressed in the review one that is relevant to dietetics practice? Yes
  4. Will the information, if true, require a change in practice? ???
Validity Questions
  1. Was the question for the review clearly focused and appropriate? Yes
  2. Was the search strategy used to locate relevant studies comprehensive? Were the databases searched and the search termsused described? ???
  3. Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified andappropriate? Wereselectionmethods unbiased? ???
  4. Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methodsspecified,appropriate, andreproducible? ???
  5. Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined? ???
  6. Was the outcome of interest clearly indicated? Were other potential harms and benefits considered? Yes
  7. Were processes for data abstraction, synthesis, and analysis described? Were they applied consistently acrossstudies and groups? Was thereappropriate use of qualitative and/or quantitative synthesis? Was variation in findings among studies analyzed? Were heterogeneity issued considered? If data from studies were aggregated for meta-analysis, was the procedure described? ???
  8. Are the results clearly presented in narrative and/or quantitative terms? If summary statistics are used, are levels ofsignificance and/or confidence intervals included? Yes
  9. Are conclusions supported by results with biases and limitations taken into consideration? Are limitations ofthe review identified anddiscussed? ???
  10. Was bias due to the review's funding or sponsorship unlikely? ???