Sunday, August 17, 2014

Low Carb Diet Trials: Dansinger, et al (2005)

 
Participants and Diets
 
160 participants with BMI between 27-42 and at least 1 metabolic risk factor (high cholesterol, trigs, glucose or blood pressure, or being treated for at least one of them) were randomised to one of four diet groups: Atkins, Zone, Weight Watchers or Ornish.  The groups were similar at baseline although the Zone and Ornish groups had almost significantly higher insulin
 
Diet Group
Diet Advice
Atkins
< 20g carbs, then gradual increase to 50g
Zone
30P:30F:40C
Weight Watchers
Calorie restriction based on points (~1200-1800 kcal)
Ornish
Vegetarian diet and 10% calories from fat
 
“We encouraged all participants to take a nonprescription multivitamin daily, obtain at least 60 minutes of exercise weekly, and avoid commercial support services. To approximate the realistic long-term sustainability of each diet, we asked participants to follow their dietary assignment to the best of their ability until their 2-month assessment, after which time we encouraged them to follow their assigned diet according to their own self-determined interest level.”
 
·         The Atkins group initially reduced carbohydrates from 239g to 68g at 1 month, but returned to 190g at 6 and 12 months.  The Atkins group had the smallest reduction in calories
·         The Ornish group initially reduced fat from 75.5g to 26.5g at 1 month, but returned to 64.0g at 12 months.  Similarly, they increased fibre from 14.0g to 20.5g at 1 month but slid back down to 15.0g at 12 months
·         The Zone and WW groups maintained the largest reduction in calories, which came fairly equally from fat and carbohydrate 

 
For more information see Table 2
 
* Once again the low fibre intake (~15g) in the groups suggests they didn’t eat much whole plant foods, suggesting the overall diet quality was poor
 
Results
 
In the intention to treat analysis:
 
·         All groups lost weight, but there were no differences between the groups
·         All groups lowered their LDL-C except Zone and WW at 6 months and Atkins at all time points
·         All groups increased their HDL-C at 12 months except Ornish
·         All groups lowered the LDL-C:HDL-C ratio
·         Atkins and Zone had significantly lower triglycerides at 1 month, but not at any other timepoint
·         All groups reduced CRP at 12 months except Zone (p = 0.09)
 
See table 3 below.  When missing values (from drop out) were excluded the figures remained pretty similar (see Table 4)
 
 
Adherence was an issue.  Dropout rates were 21% at 2 months, 38% at 6 months and 42% at 1 year.  At 1 year there was an almost significant difference (p = 0.08) between drop out in Atkins (48%) and Ornish (50%) compared to Zone (35%) and WW (35%).  “The most common reasons cited for discontinuation of the study were that the assigned diet was too hard to follow or not yielding enough weight loss”
 
 
Not surprisingly, adherence was associated with weight loss
 
 

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