title: Effects of supplemented isoenergetic diets differing in cereal fiber and protein content on insulin sensitivity in overweight humans.
abstract: BACKGROUND
  Despite their beneficial effects on weight loss and blood lipids, high-protein (HP) diets have been shown to increase insulin resistance and diabetes risk, whereas high-cereal-fiber (HCF) diets have shown the opposite effects on these outcomes.
  
  
  OBJECTIVE
  We compared the effects of isoenergetic HP and HCF diets and a diet with moderate increases in both cereal fibers and dietary protein (Mix diet) on insulin sensitivity, as measured by using euglycemic-hyperinsulinemic clamps with infusion of [6,6-(2)H(2)]glucose.
  
  
  METHODS
  We randomly assigned 111 overweight adults with features of the metabolic syndrome to 1 of 4 two-phased, 18-wk isoenergetic diets by group-matching. Per 3-d food protocols, the percentages of energy derived from protein and carbohydrates and the intake of cereal fiber per day, respectively, were as follows-after 6 wk: 17%, 52%, and 14 g (control); 17%, 52%, and 43 g (HCF); 28%, 43%, and 13 g (HP); 23%, 44%, and 26 g (Mix); after 18 wk: 17%, 51%, and 15 g (control); 17%, 51%, and 41 g (HCF); 26%, 45%, and 14 g (HP); and 22%, 46%, and 26 g (Mix). Eighty-four participants completed the study successfully and were included in the final analyses. Adherence was supported by the provision of tailored dietary supplements twice daily in all groups.
  
  
  RESULTS
  Insulin sensitivity expressed as an M value was 25% higher after 6 wk of the HCF diet than after 6 wk of the HP diet (subgroup analysis: 4.61 ± 0.38 compared with 3.71 ± 0.36 mg · kg(-1) · min(-1), P = 0.008; treatment × time interaction: P = 0.005). Effects were attenuated after 18 wk (treatment × time interaction: P = 0.054), which was likely explained by lower adherence to the HP diet. HP intake was associated with a tendency to increased protein expression in adipose tissue of the translation initiation factor serine-kinase-6-1, which is known to mediate amino acid-induced insulin resistance. Biomarkers of protein intake indicated interference of cereal fibers with dietary protein absorption.
  
  
  CONCLUSIONS
  Greater changes in insulin sensitivity after intake of an isoenergetic HCF than after intake of an HP diet might help to explain the diverse effects of these diets on diabetes risk. This trial is registered at clinicaltrials.gov as NCT00579657.
authors.affiliation: Department of Clinical Nutrition, German Institute of Human Nutrition, Potsdam-Rehbruecke, Germany. m.weickert@warwick.ac.uk
authors.forename: Martin O
authors.initials: MO
authors.lastname: Weickert
authors.forename: Michael
authors.initials: M
authors.lastname: Roden
authors.forename: Frank
authors.initials: F
authors.lastname: Isken
authors.forename: Daniela
authors.initials: D
authors.lastname: Hoffmann
authors.forename: Peter
authors.initials: P
authors.lastname: Nowotny
authors.forename: Martin
authors.initials: M
authors.lastname: Osterhoff
authors.forename: Michael
authors.initials: M
authors.lastname: Blaut
authors.forename: Carl
authors.initials: C
authors.lastname: Alpert
authors.forename: Ozlem
authors.initials: O
authors.lastname: Gögebakan
authors.forename: Christiane
authors.initials: C
authors.lastname: Bumke-Vogt
authors.forename: Friederike
authors.initials: F
authors.lastname: Mueller
authors.forename: Jürgen
authors.initials: J
authors.lastname: Machann
authors.forename: Tom M
authors.initials: TM
authors.lastname: Barber
authors.forename: Klaus J
authors.initials: KJ
authors.lastname: Petzke
authors.forename: Johannes
authors.initials: J
authors.lastname: Hierholzer
authors.forename: Silke
authors.initials: S
authors.lastname: Hornemann
authors.forename: Michael
authors.initials: M
authors.lastname: Kruse
authors.forename: Anne-Kathrin
authors.initials: AK
authors.lastname: Illner
authors.forename: Angela
authors.initials: A
authors.lastname: Kohl
authors.forename: Christian V
authors.initials: CV
authors.lastname: Loeffelholz
authors.forename: Ayman M
authors.initials: AM
authors.lastname: Arafat
authors.forename: Matthias
authors.initials: M
authors.lastname: Möhlig
authors.forename: Andreas F H
authors.initials: AF
authors.lastname: Pfeiffer
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D000328:Adult; D000368:Aged; D001794:Blood Pressure; D004043:Dietary Fiber / Q000008:administration & dosage*; D004044:Dietary Proteins / Q000008:administration & dosage*; D019587:Dietary Supplements; D002523:Edible Grain; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D050177:Overweight / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D004043:Dietary Fiber; D004044:Dietary Proteins