title: Effects of a low-glycemic load vs low-fat diet in obese young adults: a randomized trial.
abstract: BACKGROUND
  The results of clinical trials involving diet in the treatment of obesity have been inconsistent, possibly due to inherent physiological differences among study participants.
  
  
  OBJECTIVE
  To determine whether insulin secretion affects weight loss with 2 popular diets.
  
  
  METHODS
  Randomized trial of obese young adults (aged 18-35 years; n = 73) conducted from September 2004 to December 2006 in Boston, Mass, and consisting of a 6-month intensive intervention period and a 12-month follow-up period. Serum insulin concentration at 30 minutes after a 75-g dose of oral glucose was determined at baseline as a measure of insulin secretion. Outcomes were assessed at 6, 12, and 18 months. Missing data were imputed conservatively.
  
  
  METHODS
  A low-glycemic load (40% carbohydrate and 35% fat) vs low-fat (55% carbohydrate and 20% fat) diet.
  
  
  METHODS
  Body weight, body fat percentage determined by dual-energy x-ray absorptiometry, and cardiovascular disease risk factors.
  
  
  RESULTS
  Change in body weight and body fat percentage did not differ between the diet groups overall. However, insulin concentration at 30 minutes after a dose of oral glucose was an effect modifier (group x time x insulin concentration at 30 minutes: P = .02 for body weight and P = .01 for body fat percentage). For those with insulin concentration at 30 minutes above the median (57.5 microIU/mL; n = 28), the low-glycemic load diet produced a greater decrease in weight (-5.8 vs -1.2 kg; P = .004) and body fat percentage (-2.6% vs -0.9%; P = .03) than the low-fat diet at 18 months. There were no significant differences in these end points between diet groups for those with insulin concentration at 30 minutes below the median level (n = 28). Insulin concentration at 30 minutes after a dose of oral glucose was not a significant effect modifier for cardiovascular disease risk factors. In the full cohort, plasma high-density lipoprotein cholesterol and triglyceride concentrations improved more on the low-glycemic load diet, whereas low-density lipoprotein cholesterol concentration improved more on the low-fat diet.
  
  
  CONCLUSIONS
  Variability in dietary weight loss trials may be partially attributable to differences in hormonal response. Reducing glycemic load may be especially important to achieve weight loss among individuals with high insulin secretion. Regardless of insulin secretion, a low-glycemic load diet has beneficial effects on high-density lipoprotein cholesterol and triglyceride concentrations but not on low-density lipoprotein cholesterol concentration.
  
  
  BACKGROUND
  clinicaltrials.gov Identifier: NCT00130299.
authors.affiliation: Department of Medicine, Children's Hospital Boston, Boston, Mass 02115, USA.
authors.forename: Cara B
authors.initials: CB
authors.lastname: Ebbeling
authors.forename: Michael M
authors.initials: MM
authors.lastname: Leidig
authors.forename: Henry A
authors.initials: HA
authors.lastname: Feldman
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Lovesky
authors.forename: David S
authors.initials: DS
authors.lastname: Ludwig
mesh_terms: D000328:Adult; D050528:Diet, Carbohydrate-Restricted; D018752:Diet, Fat-Restricted; D015444:Exercise; D005260:Female; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D008297:Male; D009765:Obesity / Q000178:diet therapy* / Q000378:metabolism*; D017060:Patient Satisfaction; D015431:Weight Loss
chemical_list: D007328:Insulin